Introduction
A war crime can be defined as a serious violation of the laws or customs of war for which the perpetrator incurs individual criminal responsibility as a direct result of the operation of international law.Footnote 1 This definition implies that a war crime is made up, normatively speaking, of three general elements, Firstly, there is an armed conflict (including situations of occupation), which triggers the application of the laws of war in the area concerned; secondly, within that context, an act is committed that is in violation of international humanitarian law (IHL) and is materially connected to that conflict (or occupation) (“nexus”Footnote 2); and thirdly, international law recognizes such conduct as criminal and as engaging the perpetrator’s individual criminal responsibility.Footnote 3
Explaining the process by which this category of crimes came to be recognized by international law, it has been observed that
[b]efore there could be crimes of war there had to be laws of war. Before there could be laws of war there had to be customs of war. Before there could be customs of war there needed to be some sense that war had limits.Footnote 4
The history of the notion and law of war crimes is indeed a layered affair where one normative development led to the next.Footnote 5 Loose principles regulating the conduct of belligerents slowly turned into standing prohibitions; prohibitions came to be tied to legal consequences, including reparation, reprisals, and later legal responsibility; legal responsibility was first that of the sovereign, kings and States, before it reached individuals as well. This chain of normative events eventually led to the recognition of a corpus of prohibitions that form part of the laws of war and whose breach can engage the individual criminal responsibility of those who have violated them.Footnote 6 These came to be known as war crimes.
This process of transformation from loose principles into international crimes took several centuries, during which the law was made to evolve and adapt in order to address new challenges and circumstances: new types of wars, new methods of warfare, new fighting entities and new ways of inflicting harm.Footnote 7 As far as the Western hemisphere is concerned, the first identifiable stage of this process can be located somewhere between the late twelfth century and the first part of the thirteenth century, although some have chosen to place it even earlier.Footnote 8 This phase extends through the Middle Ages and up to the eighteenth century, when early principles and prohibitions regulating the conduct of warfare started taking juridical shape.Footnote 9 That body of rules became a great deal more sophisticated and uniform in the second half of the nineteenth century, when it was recorded into domestic codes and articles of war; instances of enforcement in respect of individual violators occurred with increasing frequency in the latter part of the nineteenth century and the early years of the twentieth century (phase 2).Footnote 10 Normative developments then shadowed the first international codifications of principles of IHL, without the notion of war crimes being a central element of that process (phase 3). The idea of international criminalization grew in relevance during the First World War, when the need for credible and individualized enforcement of the laws of war became ever more pressing (phase 4), and eventually took its fuller, modern shape in the context of prosecutions linked to the Second World War (phase 5).Footnote 11
Two more phases are important to the history of the law of war crimes. The sixth phase was one in which earlier developments of that law, which had taken place mostly in decentralized and piecemeal fashion, were codified in part and universalized through a process of recognition and specification in the 1949 Geneva Conventions and their Additional Protocol I (AP I) of 1977. The seventh and final phase started with the ad hoc tribunals for the former Yugoslavia and Rwanda, passed through the Rome Statute of the International Criminal Court (ICC), and then continued its path through domestic legislations, criminal prosecutions, and treaties and other international instruments. During that last phase, the law of war crimes became more certain, detailed and specific, expanded into new territories, recognized multiple categories of war crimes as forming part of international law, and shed many of the normative constraints that until then had limited the practical effect and applicability of the notion of war crimes. These successive phases are best understood as a process during which legal norms developed, expanded and changed in response to external pressures to eventually give normative shape to a body of criminal prohibitions rooted in the laws of war. This article will discuss the principal historical signposts of that process.
The present “history” of the notion of war crimes can only hope to constitute a partial and necessarily selective contribution to a broader historical canvass. There are other historical events, people, works of scholarship and sources (in particular, non-Western sources) that this paper fails to mention and which have contributed to giving shape to the notion of “war crimes”. Other scholars will hopefully study and highlight those in order to further refine our understanding of this important category of international crimes.
The slow process of criminalization of violations of the laws of war: From the twelfth century onwards
The beginning of the normative process that would eventually lead to the recognition of a category of international crimes known as “war crimes” can reasonably be placed in the twelfth and thirteenth centuries, at least as far as Europe and the Western hemisphere are concerned. At that point in time, norms regulating the conduct of men in war became increasingly associated with the threat of punishment for those violating these standards. In 1190, for instance, Richard I of England issued an ordinance that sought to regulate, under threat of harsh punishment, the conduct of soldiers and sailors in their voyage to the Holy Land.Footnote 12 While not strictly speaking a law regulating war, the ordinance was a clear assertion of civilian authority over the conduct of the troops and an early illustration of punitive enforcement of military discipline. In 1268, Prince Conrad III, Duke of Swabia, was put to trial and executed by Charles of Anjou for waging war illegally.Footnote 13 Again, while these proceedings could hardly be described as a war crime trial, they hinted at the idea that the waging of war in contradiction to accepted standards of conduct was not just a matter of politics, but one relevant to law as well.
In 1279, the Statute of Westminster laid out the general principle that soldiers were to be punished according to the law and customs of the realm.Footnote 14 The conduct of military men would thus be subject in principle to the same general set of normative limitations and prohibitions applicable to all, creating a general legal framework around the activities of the military and the conduct of its members. Three decades later, an English court tried Sir William Wallace, the Scottish nationalist, for what in effect amounted to alleged violations of the laws of war as well as treasonous acts. Wallace was charged in particular with exceeding the normative remits of lawful warfare when he allegedly indiscriminately slaughtered protected categories of individuals, including women, children and religious men.Footnote 15 In 1385, King Richard II of England adopted the Ordinance for the Government of the Army; this instrument contained various prohibitions applicable to members of the king’s forces, including violence against women and churchmen, the burning and destruction of houses and the desecration of churches and other sacred objects, threatening severe punishment and death (by hanging) in respect of some of these acts.Footnote 16
Around the same time (1393), in another part of Europe, the Federal Diet of Switzerland was adopting a document known as the Covenant of Sempach. This treaty was drawn up in the aftermath of the Battle of Sempach (1386), in which Swiss troops had successfully defeated Habsburg forces. Following indications that members of the Swiss force had engaged in insubordination and plunder, the Covenant was intended to set general rules of conduct for those fighting on behalf of the Swiss Cantons and to ensure that discipline was regulated by clear legal standards. The Covenant was, in effect, a basic military code, binding on a political and military coalition, that provided for certain restraints of a humanitarian sort on the conduct of the troops. In particular, the Covenant contained prohibitions on individual acts of spoliation, regulated matters of military discipline, provided for jurisdiction and punishment in respect of those who violated its terms, and provided for the protection of the wounded, places of worship, and women and girls – the latter point explains why it was sometimes referred to as the “Charte des Dames” (“Ladies’ Charter”).Footnote 17
A short time later (1419), Henry V, King of England, adopted similar regulations for his forces. Like their predecessors, these rules regulated matters such as the protection of the church and of women (including from rape), the rights and treatment of prisoners, and the use and taking of property; disobedience to these prohibitions was subject to punishment, including the death penalty.Footnote 18 Similar military codes, providing basic guidance for men in arms and core prohibitions in respect of their conduct, were later issued by other European leaders,Footnote 19 including Charles VII of France in 1439,Footnote 20 Ferdinand of Hungary in 1526, Emperor Maximilian II in 1570, King Gustavus II Adolphus of Sweden in 1621,Footnote 21 and James II in 1686.Footnote 22 King Gustavus’ Articles of War (1621) were particularly detailed, regulating many aspects of the life of the soldier and providing for specific prohibitions that would, through repetition and acceptance, come to form core elements of the laws of war.Footnote 23
These codes were significant attempts to moderate the hardship of war.Footnote 24 They increasingly drew a distinction between individuals participating in war, who could be attacked and killed, and the general population, who should in general be spared from violence.Footnote 25 They also built up the idea that violence, even between warring forces, was not without limitations and that certain categories of warriors who had lost the ability to fight (prisoners and the wounded and sick, in particular) should suffer no harm once rendered powerless.Footnote 26 Some of the later codes also provided what has been described as “the rudiments of what would become a regular judicial process for the ascertainment of guilt” and thus an institutionalized enforcement of the idea of personal responsibility.Footnote 27 Finally, they inspired a new idea: namely, that individuals and not just States or kings were bound by the laws regulating wars, and that an individual breaching those laws could bear personal responsibility for doing so.
In 1625, echoing those ideas, Hugo de Groot, dit Grotius, wrote about the possibility of individuals being held accountable for violating the law of nations.Footnote 28 Emer de Vattel similarly underlined the limits that the law regulating war placed upon belligerents and pointed to “this rule of justice and humanity” that was binding upon all nations and those fighting on their behalf.Footnote 29 De Martens likewise thought that a soldier who had committed violence unjustified by his charge could be denied the status of prisoner of war for that reason and be subject to punishment for it.Footnote 30 Indeed, all through that period, prosecutions of individuals such as Arnault Guilhem de Barbazan,Footnote 31 Sir Wallace,Footnote 32 Hamon Le Strange,Footnote 33 Messrs Arbuthnot and Ambrister,Footnote 34 and othersFootnote 35 for violating nascent standards of war laws helped consolidate the idea that individuals could bear responsibility, including individual criminal responsibility, in respect of those found guilty of breaching those laws.
When considered together, these codes, pronouncements and prosecutions solidified the idea that war was regulated by law and that breaches of that law could engage a perpetrator’s responsibility.Footnote 36 They also amplified and clarified the scope of what was prohibited in war and, through repetition, crystallized and, in a loose manner, “codified” certain core prohibitions that would come to constitute central tenets of the laws of war and of the law of war crimes (e.g., the prohibitions against pillage, attacks on hospitals and churches, and violence to women, prisoners and the wounded). Finally, they reflected the idea of a common humanity that set some limits to the lawful exercise of military violence and recognized as common to all certain basic protections that likewise reflected this idea.Footnote 37
In the latter part of the eighteenth century, these developments started finding their way into so-called “articles of war” adopted by various nations to regulate the conduct of their forcesFootnote 38 and in treaties binding on those nations. Thus, the 1785 and 1799 treaties between Prussia and the United States did not provide for penal sanctions, but they included prohibitions of a humanitarian sort which would later come to be recognized as core prohibitions of IHL and provide the normative foundation for certain categories of war crimes.Footnote 39
The nineteenth century and international codification
The nineteenth century
The next relevant stage of normative development of the law of war crimes occurred between the middle and the end of the nineteenth century, when three principal circumstances came together to ease the further development of that body of law. First was the consolidation of State sovereignties and, within those sovereignties, the growing professionalization of armies, which in turn called for laws and regulations in respect of them; second was the need for States to regulate their mutual relationships, including when at war with each other; and third was the fact that the small currents of laws and customs of war that had shaped the conduct of men of war over the past centuries were becoming increasingly uniform and consistent across Western nations, thus facilitating the process of finding common normative grounds between them. Three important codifying instruments of that era reflect these trends: General Dufour’s 1847 instructions, the 1864 First Geneva Convention, and Francis Lieber’s 1863 Code.
In November 1847, Switzerland was briefly at war. A federal army, led by General Guillaume-Henri Dufour, was facing a force of up to 80,000 men of the Sonderbund alliance, a group of seven mostly Catholic cantons linked by a secret military alliance and secessionist ambitions.Footnote 40 On 4 November, General Dufour issued detailed instructions to his subordinates regarding their expected conduct, treatment of prisoners, and the conduct of hostilities.Footnote 41 This was a code of humanitarian moderation, protective of the vulnerable and demanding restraints in the conduct of war, giving particular protection to the population, religious buildings, local officials, and wounded soldiers and prisoners.Footnote 42 In a post scriptum, Dufour also placed upon military superiors the responsibility to ensure compliance by subordinates with his instructions:
Superior commanders should endeavor to inculcate these principles in their subordinates; and these in the lower officers so that from there they may pass on to the soldiers and serve as a rule for the entire army. It must do everything to prove to the world that it is not a collection of barbarians.Footnote 43
These instructions were reiterated by General Dufour over the course of the following days and weeks.Footnote 44 Within a month, the war had been won by Dufour’s side, with only limited casualties on both sides and the Confederation intact.
These events and other local incidents of war would have an immediate rippling effect on the laws of war. In 1863, in the aftermath of the Battle of Solferino, the organization that would become the International Committee of the Red Cross (ICRC) was created with the sole objective of protecting and giving assistance to victims of armed conflicts and civil strife.Footnote 45 General Dufour would be instrumental in the creation of the ICRC and became, together with Henry Dunant and Gustave Moynier, one of the organization’s early leaders and promoters.Footnote 46 These men immediately set about drawing up a convention that would reflect the ICRC’s humanitarian ideals, leading, a year later (1864), to the adoption of the First Geneva Convention, which laid out a number of basic legal principles seeking to protect the wounded in armies in the field and those (ambulances, hospitals, medical personnel, local civilians) that seek to come to their aid.Footnote 47 In doing so, the 1864 Geneva Convention participated in the slow process of humanization of the law regulating war that was occurring in that period.Footnote 48 This process of humanization resulted in the increasing disapproval of excessive and parasitical violence unrelated to any successful military campaign;Footnote 49 this would constitute a central ingredient of the law of war crimes, which seeks to sanction and punish acts regarded as inhumane, as contrary to human dignity or as going beyond military necessity. While the 1864 Convention was rather modest in its ambitions, it provided for a dual mechanism of enforcement: it called for the intervention of a neutral intermediary to see that the humanitarian principles embodied in the new treaty were respected,Footnote 50 and it placed certain important obligations of compliance and implementation upon high-ranking military officers.Footnote 51 The Convention did not, however, provide for any punitive mechanism for breaches of its terms.Footnote 52
In 1868, an important agreement prohibiting the use in warfare of a particular type of projectiles (those weighing less than 400 grams that are explosive or charged with fulminating or inflammable substances) was established.Footnote 53 It came to be known as the St Petersburg Declaration, after the city in which it was adopted,Footnote 54 and its preamble provided for two important elements that would in due course contribute to the law of war crimes. The first of these was the prohibition of arms causing unnecessary suffering, which set a strict and normative limit to the methods and means that could be used in pursuit of military victory and would later crystallize into a specific category of war crimes.Footnote 55 The second was the preamble’s reference to “the laws of humanity” as a relevant normative restriction on warfare, which augured the Martens Clause of the Hague Conventions and would, a century later, become an important normative device that would shape various aspects of the law of war crimes.Footnote 56
The limitations and shortcomings of the regime of enforcement attaching to this nascent body of law were clear to all, and in the years that followed, the then president of the ICRC, Gustave Moynier, among others, started calling for the establishment of an international tribunal for the repression of breaches of the First Geneva Convention and articulated a principle of individual criminal responsibility in respect of breaches of the laws of war.Footnote 57 The fact that there were violations of the laws of war that qualified as criminal offences was also highlighted by others during that period, including Professor Johann Caspar Bluntschli, who, in 1866–72, used the notions of war crimes and war criminal (Kriegsverbrechen and Kriegsverbrecher in German) to describe a particularly serious sort of violation of the laws of war that engages the personal responsibility of its perpetrators.Footnote 58 These were among the earlier formal acknowledgments of the bridge that was being built between the laws of war and an associated body of criminal law. They coincided with a growing opposition to the use of reprisals and retaliation as means of enforcement of the laws of war, as these were seen as increasingly counterproductive and as generating more violence rather than less.Footnote 59 The slow rise of the idea of individual criminal responsibility in respect of violations of the laws of war also reflected the erosion of the proposition that war was a matter of normative concern to States only; war and the law regulating it were increasingly seen as also involving the rights and obligations of men.
Parallel normative developments were taking place in the New World. In the late eighteenth century and the early part of the nineteenth century, the United States adopted its Articles of War – i.e., early iterations of rules and principles regulating the conduct of war. The American Articles of War were adopted in 1775 and were quickly followed by successive revised versions.Footnote 60 These early normative attempts to regulate the life and conduct of the US military dealt with a variety of practical and disciplinary issues,Footnote 61 establishing, in particular, a number of principles regulating the responsibility of military officers in respect of the discipline and punishment of subordinates, thereby laying down another piece of what would in time become the doctrine of command responsibility.Footnote 62 A variety of cases of that era – some civil, some penalFootnote 63 – as well as military regulationFootnote 64 helped further crystallize the idea that the laws regulating war set normative limits on the conduct of both men and nations and that certain categories of departures from those norms could engage the legal responsibility of the culprits.Footnote 65
The US Civil War (1861–65) would give further impetus and urgency to these normative developments. The Civil War witnessed significant advances in the regulation of war and important instances of enforcement of the new law of armed conflict, and it soon became apparent that the Articles of War which were in force in the United States at the time were inadequate to regulate that conflict. A German entrepreneurial immigrant by the name of Francis Lieber and a small group of military men were tasked by General Henry Halleck and Secretary of War Edwin Stanton with revising the Articles of War to make them fit for purpose. Their brief quickly morphed into a request to draft a “code of regulations” drawn from the laws and usages of war that would regulate the conduct of troops in the ongoing conflict.Footnote 66 Lieber was the main author of that document, which he compiled from different sources, adding his own style and language to a hodge-podge of principles, prohibitions and obligations. On 24 April 1863, President Lincoln promulgated this code, as reviewed and edited by General Halleck, as General Order No. 100, under the title of Instructions for the Government of Armies of the United States in the Field.Footnote 67 The Lieber Code contained, expressed, consolidated and reformulated a great number of modern ideas regarding the regulation of war that would come to constitute central tenets of the laws of war and set the general outlines of the criminalized parts of that law.Footnote 68 Particularly important to the law of war crimes, the Lieber Code prohibited certain basic violations of the laws of warFootnote 69 and provided personal sanctions in respect of those who committed such acts.Footnote 70 The Code was also significant in that it contained repeated references to criminal punishment in relation to certain categories of violations of the prohibitions which it contained.Footnote 71 This, no doubt, echoed both the experience of violence of earlier conflicts and the fact that the armies on both sides of the Civil War were for the most part made up of inexperienced and untrained citizens who might not be all that prepared to comply with military discipline.Footnote 72 In that sense, the Lieber Code provided an important reminder to the troops that the responsibility to comply with the laws of war was also individual and that punishment awaited those who failed to comply with those laws.Footnote 73 That reminder was backed by a set of provisions on military justice, not least Article 13, which put some necessary institutional and procedural meat onto the normative bone.Footnote 74 The Code also highlighted in clear terms the right and obligation of each belligerent to punish those who violated its standards, thus auguring the regime laid out a century later in the 1949 Geneva Conventions in respect of so-called grave breaches of those Conventions.Footnote 75
The US Civil War also witnessed hundreds if not thousands of prosecutions in respect of acts regarded as being in violation of the applicable laws of war, not least in respect of acts of treason, conspiracies against the Union, and spying.Footnote 76 There were also prosecutions of violations of the laws of war in respect of the mistreatment and detention in inhumane conditions of Union prisoners.Footnote 77 These cases support the general proposition that, at that point in time already, there was little doubt that certain categories of violations of the laws of war were regarded as criminal offences which could engage the responsibility of those who commit them and that such individuals could be prosecuted by competent authorities, particularly courts-martial and military commissions.Footnote 78 They also highlight and underline the growing acceptance that military commanders carried certain responsibility of control in relation to their subordinates.Footnote 79
This era contributed enormously to the development of the law of war crimes. First, it created a normative impetus which, as will be discussed next, made it possible for States to discuss and agree upon a set of rules that would regulate warfare. Second, this early phase helped to crystallize a number of core, basic elements of the laws and customs of war that were generally accepted and which would form the foundation of international codificatory efforts over the following decades. In particular, the period sanctioned three related elements that form central tenets of the notion of war crimes: (1) the principle that certain violations of the laws of war constitute criminal offences, (2) the associated principle of individual criminal responsibility whereby an individual committing or taking a culpable part in the commission of such acts can be prosecuted and held criminally responsible for it, and (3) the right and possibility for a belligerent to exercise jurisdictional competence over such acts, whether committed by a national or the national of a foreign country.Footnote 80
Origin of the phrase “war crimes”
There has been some dispute regarding the attribution of the first use of the phrase “war crime” and whether credit for it should go to Johann Caspar Bluntschli or to Francis Lieber.Footnote 81 The debate does little to elucidate the notion of war crimes and, in any case, appears to constitute a distortion of reality. First, the branding or naming of criminalized violations of the laws of war as “war crimes” is of much less significance than the recognition of the principle, irrespective of name, that certain violations of the laws of war are indeed crimes under international law. And, as is apparent from the above, this idea and proposition long predated the writings of Bluntschli and Lieber. The attribution to either of them of the first use of the expression “war crime” is also, at best, a historical shortcut. That phrase (“war crime”, “crime de guerre”, “Kriegsverbrechen”) had in fact long been in use before either of these men made use of it. For instance, in a 1711 publication of his letters and writings, Mr Esprit Fléchier, bishop of the French city of Nismes (Nîmes), wrote about an army general who, acting under the authority of his sovereign, killed an enemy of his prince. He then queried whether the general’s conduct could be considered a “crime de guerre”.Footnote 82 In his 1764–65 “portable” dictionary (Dictionnaire philosophique portatif), the French philosopher François-Marie Arouet, better known as Voltaire, discussed and mused about the topic of “war” (“Guerre”) and its many hardships; in that context, he too made use of the phrase “crime de guerre”.Footnote 83 Not long after (1769), Louis-Mayeul Chaudon, a French intellectual of more modest standing, published his own Dictionnaire anti-philosophique in response to Voltaire’s book and what he saw as Voltaire’s underlying anti-Christian attacks. In the context of discussing whether Christian “orators” (i.e., intellectuals or public figures) had spoken against the scourge of war, he likewise used the phrase “crime de guerre”.Footnote 84
The 1788 record of Des États généraux, et autres assemblées nationales Footnote 85 discusses the various species of “revolutionary crimes” (“crimes révolutionnaires”) and lists among them the notion of “crime de guerre”, describing such acts as those taken against insurgents fighting for freedom and liberty.Footnote 86 These are crimes, the record makes clear, that are punished on the battlefield and not outside of it.Footnote 87 In the German-speaking world, the same phrase had perhaps been used as early as 1669, if not before;Footnote 88 Swiss military regulations of 1799 likewise referred to the notion of “war crimes”.Footnote 89 In his 1827 Neues Archiv des Criminalrechts, Christian Gottlieb Konopak and his fellow editors discussed the availability of the defence of necessity in respect of war crimes.Footnote 90 In a personal account written in 1871 of the Battle of Orléans (1870) between French and Prussian forces, one author described the indiscriminate destruction of civilian structures as a large “war crime” (“crime de guerre”).Footnote 91
By the time Bluntschli and Lieber made use of the phrase “Kriegsverbrechen”/“war crimes”, the expression was thus well known already.Footnote 92 It is apparent from the above that the phrase “war crimes”, “crimes de guerre” or “Kriegsverbrechen” was not a sudden invocation attributable to one man but un terme de son temps, an expression used in various languages and contexts that came to be increasingly accepted as the normative description of certain particularly serious violations of the laws and customs of war. It is the case, however, that both Bluntschli and Lieber were critical legal architects of that notion in the sense that they both helped to develop the idea that certain categories of violations of the laws of war were crimes under international law and helped give normative shape to this idea.
International codification of the laws and customs of war and the place of war crimes
The idea that certain violations of the laws of war were offences which could trigger the criminal responsibility of the individual perpetrators was also slowly making its way into international treaties. On the initiative of Czar Alexander II of Russia, delegates from fifteen European countries met in Brussels on 27 July 1874 and drew up an international agreement concerning the laws and customs of war prepared by the Russian government. It came to be known as the Brussels Declaration, and although it was never ratified,Footnote 93 it was an important step in the creation of a broad-based consensus in Europe regarding basic norms regulating warfare.Footnote 94 Drawn up by such eminencies as Messrs Bluntschli, Moynier and Rolin-Jaequemyns, the Declaration was described as “the reasonable expression of the obligations that the legal conscience of the European peoples imposes both on belligerent armies and occupied nations”.Footnote 95 In particular, Article 13 of the Brussels Declaration provided for a short list of “forbidden” acts, many of which would come to be regarded as recognized categories of war crimes and/or grave breaches of the Geneva Conventions.Footnote 96 In this context, one of the French delegates, General Eugène Arnaudeau, invited delegates to agree to a uniform regime of sanctions to be provided in national military codes to punish violations of international law committed by members of their armed forces.Footnote 97 While the proposal failed to gain enough support, it reflected the growing importance of individual accountability as a guarantor of the effectiveness of the laws of war.
That same year, the Institute of International Law, a scientific association founded in 1873, appointed a committee to study the Brussels Declaration and to submit additional proposals for providing humanitarian limits to war. These efforts eventually resulted in the drafting and adoption by the Institute of a manual of the laws and customs of war at Oxford in 1880.Footnote 98 Building upon the Brussels Declaration, the Oxford Manual had been drafted in large part by the ICRC’s Gustave Moynier with the stated purpose of codifying and providing an agreed set of humanitarian rules that would constrain State violence in war.Footnote 99 The Manual was a compact and innovative accounting of some of the core principles regulating war on land.Footnote 100 Interestingly, Article 84 of the Manual provided that “offenders against the laws of war are liable to the punishments specified in the penal law”,Footnote 101 though this principle was still in competition with the more traditional mode of compliance of the laws of war: reprisals.Footnote 102 The express provision of a principle of individual responsibility for lawbreakers did, however, again reflect the growing awareness of the importance of individual accountability to the overall effectiveness of the laws of war, albeit with little in the way of practical details of the proposed regime.Footnote 103
The increasing importance of the principle of individual accountability in respect of violations of the laws and customs of war at the turn of the century is also plainly illustrated by the war crimes prosecutions that multiplied around that time. Prosecutions of violations of the laws of war took place, for instance, in respect of crimes committed during the Boer War of 1899–1902,Footnote 104 but also in respect of the American anti-insurrection campaign of 1901 in the Philippines,Footnote 105 and in respect of the Franco-Prussian war of 1870–71.Footnote 106 Military regulationsFootnote 107 and treaties of the same era similarly integrated the idea of criminal punishment for violations of the laws of war.Footnote 108
The Brussels Declaration and the Oxford Manual would provide important inspiration for the process of codification of the laws of war which took place in The Hague and Geneva between 1899 and 1907. Starting with the Hague Conventions of 1907, their contribution to the law of war crimes was limited but not insignificant. In case of violations of their terms, the Hague Conventions only provided for the responsibility of States Parties to pay damages;Footnote 109 States were, therefore, left free to decide whether and how to punish acts committed by their troops or by their enemies in violation of the Conventions.Footnote 110 In this sense, the Hague Conventions could be said to “mark a return to the traditional view of relations between states as being confined to reparation for damages, and [to leave] to states the responsibility to stop and repress violations committed by members of their respective armed forces”.Footnote 111 However, the Hague Conventions were important to the development of the law of war crimes in other, perhaps less apparent, ways. First, the Conventions drew a clear enough line in respect of various aspects of the conduct of hostilities between what was regarded, as a matter of international law, to be lawful and what was not, rather than leaving that determination to be made by each belligerent for itself.Footnote 112 In doing so, they identified certain categories of acts that were regarded as unlawful under international law and whose violation would come to be regarded as war crimes in the aftermath of the Second World War.Footnote 113 Secondly, the Conventions contained a variety of obligations that were binding not just on States, but on individuals.
That international law would talk directly to individuals and bind them to certain conduct is again an important premise of a criminal law being built on the back of those obligations.Footnote 114 For instance, Article 41 of the Hague Regulations annexed to Hague Convention IV provided that the violation of the terms of an armistice by private persons acting on their own initiative entitles the injured party to demand the punishment of the offenders or, if necessary, compensation for the losses sustained.Footnote 115 Article 56(2) of the same Regulations provided for a meek but unqualified “injunction” that all seizure of, destruction or wilful damage done to institutions dedicated to religion, charity, education and the arts and sciences, as well as historic monuments and works of art and science, “is forbidden, and should be made the subject of legal proceedings”.Footnote 116 While this system was generally ineffective in ensuring actual criminalization of deviant conduct, it highlighted the growing expectation and understanding that certain particularly serious violations of the laws of war warranted criminal punishment.Footnote 117 Similarly, Article 21 of the 1907 Hague Convention X for the Adaptation to Maritime Warfare of the Principles of the Geneva Convention required States to enact penal legislation and take necessary steps to punish individual acts of pillage and ill-treatment in respect of the sick and wounded in the fleet.Footnote 118 Finally, the preamble of the 1899 and 1907 Hague Conventions contained a residual regulatory mechanism, today known as the Martens Clause, which made it clear that the Conventions were not an exhaustive iteration of the limits which international law places upon the conduct of States at war and referred in that context to the relevance of “the usages established among civilized peoples, from the laws of humanity, and the dictates of the public conscience”.Footnote 119 That clause opened up a normative territory in which IHL would grow outside the diplomatic and political constraints of positive law, and it also provided a lens that enabled the expansion of humanitarian law and the law of war crimes in a direction that built in these considerations of humanity, civilization and the public conscience. The Hague Conventions were thus significant in the history of the law of war crimes in that they reflected the growing interest of the community of States in binding individuals to certain obligations and providing sanctions in respect of a common normative group of legal prohibitions forming part of the laws of war. In so doing, they demonstrated the international community’s mounting concern for matters once exclusively situated within the protected internal affairs of States.Footnote 120
In the period between the Hague Conventions of 1899 and 1907, the Convention for the Amelioration of the Condition of the Wounded and Sick in Armies in the Field was adopted in Geneva in 1906. This was in effect a revision of the outdated 1864 Geneva Convention. The 1906 Convention updated, improved and supplemented the earlier Convention and introduced additional elements of normative regulation of war. It was also, in no small part thanks to Moynier,Footnote 121 the first international treaty to contain provisions dealing with the (indirect) repression of violations of its prohibitions, specifically abuse of the protective emblem and robbery and ill-treatment of the wounded and sick in armies.Footnote 122 Under this regime, States Parties undertook to provide in their municipal law for the criminalization of these violations.Footnote 123 This was, in effect, a penal regime à deux temps: certain conducts were identified internationally as violations of international law warranting criminal sanctions, with the normative (and prosecutorial) responsibility to turn these into penal offences being delegated to individual States.Footnote 124
The First World War and the inter-war period
The First World War
The First World War is often characterized as a failure to assert the existence and relevance of the laws of war and to enforce them in respect of those who ignored and trampled upon them during that conflict. The reality, however, is more nuanced. Normatively speaking, it was in fact a critical time for the development of what came to be known as international criminal law, if not for its enforcement. It was when a powerful group of States – with some, including the United States and Japan, still showing some reticence – formally recognized that there were violations of international law that were criminal in character, the commission of which could trigger an individual’s criminal responsibility as a direct result of the operation of international law,Footnote 125 however high-ranking or important the perpetrator.Footnote 126 In particular, an initial list of war crimes was drawn up in 1919 by an international body, the Commission on the Responsibility of the Authors of the War and on Enforcement of Penalties (Commission of Responsibilities),Footnote 127 containing the core of what is regarded to this day as war criminality. In this context, the Commission held that
[a]ll persons belonging to enemy countries, however high their position may have been, without distinction of rank, including Chiefs of States, who have been guilty of offences against the laws and customs of war or the laws of humanity, are liable to criminal prosecution.Footnote 128
This was both a clear assertion of the principle of individual criminal responsibility under international law in respect of violations of the laws of war and an unmistakable acknowledgment that no man, however important, could evade responsibility under international law if engaged in the commission of an international crime. The Commission of Responsibilities also pointed to the jurisdictional principle, already long in existence, that any belligerent would be permitted to prosecute those responsible for such acts.Footnote 129
The Versailles TreatyFootnote 130 and the Sèvres TreatyFootnote 131 recorded and furthered important normative developments going in the same general direction.Footnote 132 These treaties contained provisions that reflected the birth of a still primitive system of international criminal law.Footnote 133 Particularly important in the present context are Articles 228 and 229 of the Versailles Treaty.Footnote 134 These provisions formally recognized that certain categories of violation of the laws and customs of war were “criminal acts”, which belligerents were authorized to punish.Footnote 135 The Treaty provided separately for the creation of a specialized jurisdiction to address the responsibility of the Kaiser.Footnote 136 Prosecutions for violations of the laws of war ensued, in particular and most famously in Germany,Footnote 137 as well as in Turkey,Footnote 138 FranceFootnote 139 and other countries.Footnote 140 Many of these prosecutions were disappointing and unsatisfactory from the point of view of sheer justice; they were limited in number, often distorted by national bias and resulted in judgments that failed to establish the depth and extent of criminality witnessed during the war.Footnote 141 Some of these cases did, however, sanction important aspects of the laws of war, which would resonate loudly in the aftermath of the Second World War.Footnote 142
Three other important developments occurred during this period. First, a significant section of the international community of States recognized the existence of a core set of rules, prohibitions and principles that would later crystallize into a body of international criminal law. Particularly important to the foundations of that body was the acceptance of the idea that a breach of international law could engage an individual’s criminal responsibility as a direct result of said breach, and that an official position provided no defence against or exception to that possibility.Footnote 143 Germinating in that context was also the idea that it was not only the direct perpetrators of such crimes who could be punished for them, but also other categories of individuals who contributed to them, including those in a position of command and authority who had failed to act to prevent or punish the criminal deeds of their subordinates.Footnote 144 Once recognized, these principles could not easily be ignored, and they would instead find new resonance when dusted off and enforced in the aftermath of the Second World War.Footnote 145 Articles 227 and 228 of the Versailles Treaty, which foresaw the possibility of German criminals being tried before domestic jurisdictions or a high tribunal, were thus referred to almost three decades later by the International Military Tribunal (IMT) at Nuremberg in support of the view that international law recognized the principle of individual criminal responsibility for certain types of violations and the right of belligerents to punish such acts.Footnote 146 Similarly, in the Peleus case arising from the Second World War, the Judge-Advocate General relied as precedent upon the Llandovery Castle case, which had been tried by a German court in the aftermath of the previous war.Footnote 147
Second, normative developments of that era laid out important jurisdictional principles that would be put into action in the aftermath of the Second World War – not least a division of the labour of punishing international crimes between domestic courts and specialized international(ized) jurisdictions and the recognition of the general right of belligerents to punish those crimes.Footnote 148 In that context, the failure of the domestic courts of the countries whose nationals and officials had allegedly committed these crimes – especially Germany and Turkey – to deliver on the demands for justice highlighted the fact that the law as well as its institutions and enforcement mechanisms should be internationalized in order to increase the likelihood of justice and accountability. Following the Second World War and the experience of the previous conflict, no serious consideration was thus given to the possibility of German or Japanese courts being entrusted with the responsibility of dispensing justice for crimes committed by German and Japanese forces in the immediate aftermath of the war. Instead, Allied and internationalized courts were established for that purpose, and specialized Allied courts were drawn up with competence over crimes committed outside national borders and, on occasion, with jurisdiction in respect of crimes committed by foreigners against foreigners. This was a direct historical echo of the terms of the Versailles Treaty and the work of the Commission of Responsibilities.Footnote 149 Also, by pointing to the judicial process as a credible avenue for punishing and deterring violations of the laws of war, Allied States further eroded the sense that traditional means of enforcement of the laws of war – in particular reprisals and retaliation – could be regarded as effective means of implementation of those laws.Footnote 150
Third, the list established by the Commission of Responsibilities effectively served as a first international codification of the law of war crimes. While the thirty-two categories of crimes contained in that list were somewhat randomly put together and factually focused on the events of the last war, the list provided a first clear and broad outline of some of the conduct already recognized by international law as crimes.Footnote 151 No State involved in this process questioned whether any of the listed category of war crimes were indeed criminal offences under international law.Footnote 152 Still other categories of war crimes were identified at the time by States that were investigating the possibility of their prosecution.Footnote 153 The Commission’s list would be used after the Second World War as an authoritative – though non-exhaustive – statement of the law and serve as a normative starting point for the effective investigation and prosecution of crimes committed by officials and servants of the Nazi regime and its allies.Footnote 154
The inter-war period
While the inter-war period was not legally very fruitful as far as the laws of war and of war crimes were concerned, a few instruments are worth mentioning.Footnote 155 The 1922 Washington Conference on the Limitation of Armaments formed part of the normative legacy of the First World War and resulted in the adoption of the Treaty relating to the Use of Submarines and Noxious Gases in Warfare.Footnote 156 The treaty was negotiated by five of the victorious powers of the First World War (the United States, United Kingdom, France, Italy and Japan) but never entered into force due to France’s failure to ratify it.Footnote 157 Article 3 of that failed treaty included an important provision that can be said to have served as inspiration for future such provisions. It stated:
The Signatory Powers, desiring to ensure the enforcement of the humane rules of existing law declared by them with respect to attacks upon and the seizure and destruction of merchant ships, further declare that any person in the service of any Power who shall violate any of those rules, whether or not such person is under orders of a governmental superior, shall be deemed to have violated the laws of war and shall be liable to trial and punishment as if for an act of piracy and may be brought to trial before the civil or military authorities of any Power within the jurisdiction of which he may be found.
The provision hit on several of the points that would become core features of the regime of criminal responsibility for war crimes, providing for (1) individual in addition to State responsibility; (2) criminal responsibility for individuals arising directly from international law; (3) the irrelevance or absence of defence based on superior orders; (4) the notion of international crimes (albeit indirectly, by reference to the notion of piracy); and (5) a nascent notion of universal (albeit non-mandatory) jurisdiction over such conduct.Footnote 158
Next came the 1929 Geneva Conventions.Footnote 159 These were a missed opportunity to build upon the principles of penal responsibility outlined by the Commission of Responsibilities after the First World War. Article 29 of the Convention on the Wounded and the Sick called upon States Parties to propose to their legislatures, should their penal laws be inadequate, the adoption of necessary measures for the repression in time of war of any act contrary to the provisions of the Convention.Footnote 160 Few did.Footnote 161 Also, Article 30 of that same Convention provided for the establishment of an inquiry mechanism in case of alleged violation of the Convention; this provision contained an obligation of “repression” but proved ineffective.Footnote 162 Thus, while the 1929 Geneva Convention on the Wounded and Sick crystallized the notion that there should be some form of enforcement or sanction in respect of violations of the laws of war, it did little to secure actual individual accountability or to make that enforcement credible and effective.Footnote 163 The 1929 Geneva Convention on Prisoners of War contained no mechanism of sanctions.
Two more instruments are worth mentioning here. The first of these is the 1934 Draft Monaco Convention,Footnote 164 which was intended to reinforce the 1929 Convention on the Wounded and Sick and to provide, in particular, for a regime of protected “medical cities and localities”, for the provision of medical assistance by non-belligerent parties, and for certain protections for prisoners of war.Footnote 165 Most importantly for our present purposes, the draft treaty provided for a regime of sanctions which included provisions on investigations and penal sanctions.Footnote 166 In particular, draft Article 6 provided for the judiciarization of the responsibility of both States and individuals.Footnote 167 Less helpfully, the draft treaty also provided for recourse to reprisals and other legal measures and that in the event of serious and repeated violations of the laws of humanity, the State victim of those violations was freed of its own obligations to the same extent as its adversary.Footnote 168
The second instrument worth noting is the 1937 Nyon Agreement. This treaty was a normative echo of the Spanish Civil War, in the course of which nine powers (the United Kingdom, France, the Soviet Union, Yugoslavia, Bulgaria, Egypt, Greece, Romania and Turkey) agreed to take collective measures to suppress attacks by submarines against merchant vessels as were happening in the Mediterranean sea at the time.Footnote 169 The enforcement regime foreseen in the Nyon Agreement was a sort of mixture between penal instruments and mechanisms that described the acts which it prohibited as “acts of piracy” and “acts contrary to the most elementary dictates of humanity”, thereby echoing core elements of international criminal law. At the same time, the Agreement stated in its Article II that any submarine committing violations of its terms “shall be counterattacked and, if possible, destroyed”, and laid out a set of practical means by which such a system could be enforced. As such, and as Yves Sandoz has noted, the regime was “more a form of reprisal than a form of penal justice”.Footnote 170 A penal response was thus, at this point, still far from the only or obvious redress for violations of the laws of war.
A quantum leap: The Second World War and its aftermath
Before Nuremberg
However disappointing and unsatisfactory it may have been, the legacy of the First World War would come to play an important role during the Second World War.Footnote 171 When the first reports of Nazi and Japanese atrocities started to emerge, the view that these crimes should be subject to legal punishment went largely unquestioned amongst the Allies. The reticence aired by some States, not least the United States, at the end of the First World War was all but gone.Footnote 172 The first significant public response to the news of these crimes came in the form of parallel statements issued by President Roosevelt and Prime Minister Churchill on 25 October 1941.Footnote 173 Churchill’s declaration made express reference to the fact that “[r]etribution for these crimes must henceforward take its place among the major purposes of the war”.Footnote 174 Shortly thereafter, on 7 November 1941, Foreign Minister Molotov of the Soviet Union issued a note condemning German atrocities and calling for the punishment of perpetrators.Footnote 175 The Allied plan for retribution started taking shape with the Declaration of St James of 13 January 1942,Footnote 176 which made explicit reference to the 1907 Hague Conventions as regulating the conduct of belligerents in occupied countries, and placed among the signatories’ war aims the punishment “through the channels of organized justice” of those responsible for violating the laws and customs of war.Footnote 177 The work of the London International Assembly, a non-official body made up of members appointed by Allied governments, prepared the ground further by identifying various categories of acts prosecutable as war crimes and laying down normative, practical and procedural elements of the machine that would soon start investigating and prosecuting those crimes.Footnote 178
On 7 October 1942, the Allied governments announced that they would set up a commission for the investigation of war crimes.Footnote 179 The resulting United Nations War Crimes Commission (UNWCC) was eventually created on 20 October 1943 at a meeting of Allied nations at the British Foreign Office in London.Footnote 180 Its mandate was to investigate and record evidence of war crimes, identifying, where possible, the individuals responsible for such crimes, and to report to the Allied governments cases in which it appeared that adequate evidence might be expected to be forthcoming.Footnote 181 The UNWCC did not, however, provide a general definition of the notion of “war crimes”; in its History, it explained that it had refrained from doing so because a definition “involves limitation and exclusion”,Footnote 182 and hence the Commission “did not think it necessary or desirable to formulate a precise definition, nor did it give more than a working list”.Footnote 183 Instead, it was decided that the UNWCC would operate on the basis of the list of war crimes prepared by the 1919 Commission of Responsibilities.Footnote 184 This course of action presented the added advantage that Italy and Japan had been parties to the preparation of the list and thus accepted the general tenor of it, while Germany had never raised any objection to it.Footnote 185
Preparations for the prosecution of Nazi war crimes continued throughout the war, culminating on 30 October–1 November 1943 with the adoption of the Moscow Declaration by Roosevelt, Churchill and Stalin. The Moscow Declaration foresaw that at the end of the conflict,
those German officers and men and members of the Nazi party who have been responsible for or have taken a consenting part in the above atrocities, massacres and executions will be sent back to the countries in which their abominable deeds were done in order that they may be judged and punished according to the laws of these liberated countries and of free governments which will be erected therein.Footnote 186
The question of the meaning of “war crimes” arose again in the work of the UNWCC when the scope and nature of the crimes committed by the Axis powers became ever more apparent as information was being collected. In that context, it was initially recommended that the notion of “war crimes” under which the UNWCC operated should include the perpetration and waging of aggressive war and crimes committed, within or outside any Axis country, for the purpose of racial or political extermination.Footnote 187 While elements of the latter criminality came to be prosecuted as war crimes, a clear normative line would be drawn between war crimes stricto sensu and what came to be known as the notion of “crimes against peace” or “aggressive war”.Footnote 188
The second occasion when the meaning of “war crimes” came to be discussed by the UNWCC was in relation to the question of whether such crimes could only be committed against enemy nationals or whether the notion would also cover crimes committed by a warring party against its own nationals. Initially, the Commission took the view that war crimes could only be committed by enemies against “allied” nationals and only in relation to offences committed since the outbreak of the war in September 1939. Both propositions would be challenged as early as October 1943 at the diplomatic conference instituting the UNWCC. The Chinese delegation voiced the view that offences committed prior to September 1939 should also come within the scope of the Commission’s work. The subcommittee charged with considering the matter recognized that the elements of time and nationality were not to be regarded as absolute constraints on the work of the Commission and recommended that expansions of the reach of the law of war crimes should be considered at a later stage.Footnote 189 The issue was further considered in April 1944, when the Belgian representative to the UNWCC proposed that certain offences committed against individuals who were not “allied” nationals should also be treated as war crimes and that the nationality of the victim or place of commission of the crime should be regarded as irrelevant to the definition of this category of crimes.Footnote 190 The proposal was considered by the UNWCC in May 1944 and generally accepted by many members of the Commission. A draft recommendation to that effect was submitted by the chairman of the Commission, which favoured the proposal insofar as Danish and Italian victims were concerned, on account of the terms of the Moscow Declaration;Footnote 191 absent unanimity, however, consideration of the matter was adjourned. An initiative regarding crimes committed against stateless persons also remained unaddressed, though the UNWCC noted in its report that the principle that stateless persons could be victims of war crimes lato sensu was observed in many instances by the Committee on Facts and Evidence as deriving from the terms of the preamble of Hague Convention IV and the spirit of the Moscow Declaration. As a result, offences committed before September 1939 (for instance in China and Czechoslovakia), offences against stateless persons or enemy nationals, and offences committed by Allied nationals in conjunction with the enemy were treated by the UNWCC as war crimes “stricto sensu, and in any event as part of the notion of war crimes in a wider sense”.Footnote 192 The Commission suggested that the basis and justification for what appeared to be the expansion of the reach of the laws of war lay,
concurrently or alternatively, in the heinous nature of the offence, irrespective of whether the victim or the perpetrator was or was not an Allied national, or in the belligerent position of the country whose inhabitants were victimized, irrespective of whether the status of war was recognized or recognizable under the traditional terms of international law.Footnote 193
There remained one category of crimes that appeared to be beyond the scope of the laws of war crimes: crimes committed by a nation (or rather, by the officials and agents of that nation) against fellow nationals. In relation to such acts, the UNWCC proposed to develop a new legal concept: crimes against humanity.Footnote 194 As noted by the UNWCC,
[t]he development of the subject in the Commission took, technically speaking, the course of extending the concept of war crimes to a wider notion than that hitherto restricting it to the laws and customs of war. Accordingly, along with the notion of war crimes stricto sensu, there evolved the concept of war crimes in a wider, non-technical sense, as a common denominator devised so as to include crimes against humanity, and … also that of crimes against peace.Footnote 195
This amounted not to an extension of the notion of “war crimes” but to an extension of the mandate of the Commission that would eventually result in the recognition of a new category of international crimes known as “crimes against humanity”.Footnote 196
The Nuremberg Charter and Judgment
On 8 August 1945, the United Kingdom, United States, Union of Soviet Socialist Republics and France adopted the Agreement for the Prosecution and Punishment of the Major War Criminals of the European Axis (London Agreement),Footnote 197 annexed to which was the Charter of the IMT (Nuremberg Charter).Footnote 198 Article 6(b) of the Nuremberg Charter provided that the following acts were to be regarded as war crimes within the jurisdiction of the IMT, for which there would be individual responsibility:
War crimes: namely, violations of the laws or customs of war. Such violations shall include, but not be limited to, murder, ill-treatment or deportation to slave labour or for any other purpose of civilian population of or in occupied territory, murder or ill-treatment of prisoners of war or persons on the seas, killing of hostages, plunder of public or private property, wanton destruction of cities, towns or villages, or devastation not justified by military necessity.Footnote 199
The statutory list of war crimes was intentionally non-exhaustive (“shall include, but not be limited to”) and focused on a core group of serious crimes that involved attacks on the integrity or the physical well-being of individuals or groups of people and of property and which were thought relevant to the prosecution of the major Nazi war criminals.Footnote 200 This provision would go on to inspire the list of “grave breaches” provided a few years later in the 1949 Geneva Conventions.Footnote 201 In contrast, the Tokyo Charter, which set out the jurisdiction of the International Military Tribunal for the Far East, did not list any particular category of war crimes but instead generically referred to violations of the laws or customs of war.Footnote 202
From the statutory list of offences, the Nuremberg Tribunal developed a basic corpus of war crimes law. Responding to the defence challenge that the law that was being applied by the Tribunal was not binding on Germany as the “general participation” clause of the 1907 Hague Conventions had not been satisfied,Footnote 203 the Tribunal explained that the law that was being applied had long passed into customary international law so that limitations on its application as treaty law were without bearing on the case:
The law of war is to be found not only in treaties, but in the custom and practices of states which gradually obtained universal recognition, and from the general principles of justice applied by jurists and practised by military courts. This law is not static, but by continual adaptation follows the needs of a changing world. Indeed, in many cases treaties do no more than express and define for more accurate reference the principles of law already existing.Footnote 204
…
Several of the belligerents in the recent war were not parties to this convention.
In the opinion of the Tribunal it is not necessary to decide this question. The rules of land warfare expressed in the convention undoubtedly represented an advance over existing International Law at the time of their adoption. The convention expressly stated that it was an attempt “to revise the general laws and customs of war,” which it thus recognized to be then existing, but by 1939 these rules laid down in the convention were recognized by all civilized nations, and were regarded as being declaratory of the laws and customs of war which are referred to in Article 6(b) of the Charter.Footnote 205
The defence raised the further argument that, even if applicable, the Hague Conventions did not expressly characterize any of their violations as war crimes – i.e., criminal acts that could engage an individual’s penal responsibility. As such, it was argued that violations of the laws of war could at most engage Germany’s responsibility as a State, but not the responsibility of individual defendants. The IMT dismissed the argument in these terms:
The Hague Convention of 1907 prohibited resort to certain methods of waging war. These included the inhuman treatment of prisoners, the employment of poisoned weapons, the improper use of flags of truce, and similar matters. Many of these prohibitions had been enforced long before the date of the Convention; but since 1907 they have certainly been crimes, punishable as offences against the laws of war; yet the Hague Convention nowhere designates such practices as criminal, nor is any sentence prescribed, nor any mention made of a court to try and punish offenders. For many years past, however, military tribunals have tried and punished individuals guilty of violating the rules of land warfare laid down by this Convention.Footnote 206
Focusing specifically on the list of war crimes contained in Article 6(b) of the Nuremberg Charter, the IMT added that it was
of course bound by the Charter, in the definition which it gives both of War Crimes and Crimes Against Humanity. With respect to War Crimes, however, as has already been pointed out, the crimes defined by Article 6, section (b), of the Charter were already recognized as War Crimes under International Law. They were covered by Articles 46, 50, 52, and 56 of the Hague Convention of 1907, and Articles 2, 3, 4, 46, and 51 of the Geneva Convention of 1929. That violations of these provisions constituted crimes for which the guilty individuals were punishable is too well determined to admit of argument.Footnote 207
The affirmation by the IMT that these prohibitions were part of customary international law and sanctioned as criminal offences was extraordinary for various reasons. First, there was international law binding not just on States but also on individuals, and it was binding on them outside of and in addition to treaty prohibitions and independent of domestic law.Footnote 208 Second, that law was universal in character and, if violated, had penal consequences for its violators;Footnote 209 this reasoning was the implicit reflection of the Tribunal’s famous holding that “[c]rimes against International Law are committed by men, not by abstract entities, and only by punishing individuals who commit such crimes can the provisions of International Law be enforced”.Footnote 210 Third, the Tribunal’s holdings were a significant and conscious normative advance into the territoire réservé of State sovereignties.Footnote 211 New crimes were being created and defined by international law, and made superior to and detached from domestic law.Footnote 212 The novelty was also jurisdictional in character as it made it clear that the right to prosecute such acts belonged not just to the country of nationality but to all nations which have an interest in the punishment of those crimes.Footnote 213 In that context, the relevance of the Versailles Treaty as a “precedent” for the idea that the punishment of such crimes was in the interest of the community of States as a whole was duly noted by the Tribunal.Footnote 214 The UNWCC summarized this as follows:
It is by no means a novel principle in international law that the sovereignty of one State does not prevent the punishment of crimes committed against other States and their nationals. The laws and customs of war are not a restriction on state sovereignty. They regulate the relationship between one State and persons who are not subject to its sovereignty.Footnote 215
Commenting upon the IMT Judgment, the UNWCC was content to support the Tribunal’s view that the law of war crimes which was applied to the major war criminals had been pre-existing law.Footnote 216 Arguably, this conclusion was somewhat generous. The criminalization of many of those acts, which were already recognized as prohibitions under the laws of war, benefited from a good dose of judicial legislating. It is true that there had been growing acceptance that the violation of a core group of prohibitions forming part of the laws of war was to be regarded as a crime under international law,Footnote 217 but the status of these prohibitions as customary international law had remained uncertain. In recognizing the existence of a variety of war crimes binding on all as a direct result of international law, the Tribunal gave normative sanction to the moral outrage of the international community by declaring those to be crimes under international law and recognizing that their commission would engage the individual responsibility of their perpetrators as a direct result of international law.
The Nuremberg and Tokyo Judgments also helped to expand the reach of the law of war crimes in several directions. Ratione materiae, they gave judicial recognition as war crimes to a whole new range of prohibited conduct the status of which as criminal offences under international law had in some cases been uncertain until then.Footnote 218 The categories of crimes recognized as war crimes during that period were not the result of any in-depth evaluation of the state of the law but were rather a consequence of the Allies having used a juridical mirror to identify offences necessary to sanction the criminality of their enemies. In contrast, questionable methods of warfare that had also been used by the Allies, and not just by the Axis powers, often escaped criminalization.Footnote 219 The expansion of the law was also apparent ratione loci and ratione personae. Counsel for the Nuremberg defendants submitted that Germany had ceased to be bound by the laws of war once occupied territories came to be subjugated and integrated into the Reich. The IMT set aside those submissions and made clear that the laws of war continued to apply to occupied territory – incorporated or not – and provided strict protection to its population.Footnote 220 Ratione personae, the law of war crimes had until then generally been understood as criminalizing violations of the laws of war committed by nationals of a belligerent against enemy nationals, but this period witnessed clear signs of porosity towards the protection of categories of individuals other than enemy nationals.Footnote 221 During the work of the UNWCC, a proposal was thus put forward to allow the Commission to investigate not just crimes committed by the Nazi regime against Allied nationals but also nationals of States who were formally allied to Germany, including Italian hostages, and nationals of Denmark, Hungary, Romania and other neutral, co-belligerent or enemy countries.Footnote 222 While there was no legal objection to such a possibility, it was never formally adopted.Footnote 223 The fact that this was legally permissible under existing law – i.e., that the laws of war were not limited, ratione personae, to crimes committed by individuals associated with one party against enemy nationals – was also apparent from the IMT Indictment, which included charges pertaining to crimes committed by German forces against Danish and Italian nationals.Footnote 224 This process would eventually result in the disappearance of most of the distinctions drawn by the law of war crimes between different categories of victims on grounds of nationality or the “side” to which they belong.
These jurisdictions – and many others after them – also eliminated, reduced in scope or relegated to the status of mitigating factors a number of defences, exceptions and justifications (immunities, superior orders, acts of State, primacy of domestic law, duress) that had until then shielded individuals from personal liability in respect of violations of international law. The disappearance or erosion of these exceptions to liability effectively expanded the range of conduct and individuals subject to the demands and sanction of international law.Footnote 225 International crimes were, in effect, crimes that knew no personal exception. The promise of the First World War that men would be held responsible for their actions “however high their position …, without distinction of rank, including Chiefs of States”, was now being effectively vindicated.Footnote 226
The law of war crimes that came out of Nuremberg and subsequent prosecutions was, however, in need of further clarification.Footnote 227 It was still infused with considerable concern for the sovereignty of States and failed to expand on the means and methods of warfare. What the law of war crimes lacked in normative sophistication at this stage, however, it compensated for with a regime that was simple and free of many of the intricate distinctions that the laws of war born from the 1949 Geneva Conventions would inject into that regime. This made the law particularly effective for the purpose of criminal prosecution – it left little room for arguments regarding the lawfulness of war crimes as then conceived and defined, and had little time for legalistic defences.
From the 1949 Geneva Conventions to the International Law Commission’s Draft Code Of Crimes
From Nuremberg to Geneva
The principles that came out of the Nuremberg process were particularly significant as they were the judicial and normative expression of the collective interest of the international community in prosecuting and punishing international crimes.Footnote 228 This endowed them with a special status that almost immediately led to their recognition as customary international law.Footnote 229 Nuremberg and Tokyo were of course not the only prosecutions for war crimes following the Second World War; many trials also took place in domestic jurisdictions, building upon the normative and judicial legacy of these two international trials and adding their own contributions to this collective enterprise.Footnote 230 When compared to these national prosecutions, the Nuremberg and Tokyo proceedings carry with them a particular aura – that of the first truly international war crimes trials tried on behalf of a universal or at least collective community of interests. As precedent, they are therefore truly foundational: they stated the law, set it out, made it general and universal in reach and relevance, and served as a starting point for further developments.
The enthusiasm for international criminal law was soon on the wane, however. While the notion of genocide was codified in 1948,Footnote 231 no convention on crimes against humanity or crimes against peace was adopted and no permanent international criminal court was set up at that point. And while the Nuremberg proceedings helped crystallize some of the core elements of what came to be known as international criminal law, the Nuremberg Principles that were drawn from them did little to solidify and develop the law of war crimes.
The 1949 Geneva Conventions and their 1977 Additional Protocols
The fast-shrinking interest in the criminalization of the laws of war was in full view during the negotiation of the 1949 Geneva Conventions.Footnote 232 At the time of the adoption of the Conventions, there still was broad agreement with the suggestion that certain categories of serious violations of the laws of war could engage the individual responsibility of those concerned.Footnote 233 There was also a common acceptance that a system of sanctions should be built into the Conventions to provide a degree of deterrence and the possibility of enforcement of individual punishment for rule-breakers.Footnote 234 However, consensus could not be reached at the time for the creation of an international jurisdiction that would be responsible for the punishment of such acts.Footnote 235 In its place, the Conventions provided for a two-tiered regime that distinguished between two categories of violations: so-called “grave breaches” of the Conventions, which are exhaustively listed and which are war crimes by another name; and other breaches of the Conventions that do not fall within the first category. In relation to the latter “non-grave breaches”, the Conventions only foresee an obligation on the part of High Contracting Parties to ensure that such breaches cease.Footnote 236 In contrast, the Conventions provide for a number of specific obligations in respect of grave breaches which are intended to provide an effective mechanism for the investigation and punishment of such acts. States are obliged under that regime to adopt legislation capable of enforcing the regime of grave breaches foreseen by the Conventions,Footnote 237 to search for and detain individuals suspected of such acts,Footnote 238 and, where they are detained, to either prosecute or extradite the individuals concerned.Footnote 239 And while the Conventions do not provide for an international jurisdiction, they do provide for the second-best jurisdictional arrangement in the form of a system of mandatory universal jurisdiction.Footnote 240 That regime of repression was provided in respect of “grave breaches” only, and only in relation to situations of international armed conflict (including occupation). In this sense, the Geneva Conventions provided for a regime that combined criminal responsibility (in respect of individuals)Footnote 241 with a provision that excluded the possibility for a State to absolve itself or another State for liability incurred as a result of the commission of grave breaches of the Conventions.Footnote 242 The effective implementation of the criminal part of that regime was left to the responsibility of contracting States.
However, some of the same States that had so keenly broken new legal ground to prosecute former enemies a few years earlier were much less keen to tie themselves to a supranational body of criminal law and resisted the inclusion of any reference to the notion of war crimes in the Geneva Conventions.Footnote 243 In its stead, a new concept of “grave breaches” of the Conventions was used to describe what, in effect, were a particularly serious sort of violations of IHL.Footnote 244 The irony of the situation – recognizing certain violations as in effect being “war crimes” but making sure to call them something elseFootnote 245 – was compounded by the fact that the list of “grave breaches” was heavily inspired by those categories of violations recognized as war crimes at Nuremberg.Footnote 246 And while providing for the first bare-boned regime regulating non-international armed conflicts, the Conventions also failed to arm that regime with an equivalent quasi-penal regime applicable to this particular sort of armed conflicts.Footnote 247 It would take fifty years to correct this omission.Footnote 248
At the time of its adoption, the “grave breaches” regime of the Geneva Conventions was generally perceived as a positive development. It was noted that it was the first conventional criminalization of violations of the laws of war,Footnote 249 and it imposed upon States a number of strict and demanding legal obligations which it was hoped would render the enforcement of these prohibitions effective. As time has passed, however, the assessment of this regime has grown more negative.Footnote 250 Overall, hindsight suggests that the 1949 Geneva Conventions and, in particular, their “grave breaches” regime were an important, albeit somewhat disappointing, advance for the law of war crimes. First, they provided a conventional acknowledgment that the violation of certain prohibitions of IHL could carry individual penal consequences for the rule-breakers;Footnote 251 arguably, this limited achievement from the point of view of international criminal law was a significant one from the point of view of IHL, particularly when combined with the set of obligations binding on High Contracting Parties in relation to those breaches. The list of conducts recognized as amounting to criminalized violations of the laws of war was, however, far from exhaustive, omitting in particular conduct of hostilities war crimes that had already been carefully ignored in the prosecutions of the Second World War.Footnote 252 Nor was the list of grave breaches contained in the 1949 Conventions a complete reflection of those categories of war crimes that had by then been recognized as crimes under international law since at least the First World War – it was in effect the reflection of a minimum common denominator that States were willing to recognize as being relevant to their own conduct. This minimalist approach has had a rather deleterious effect on the development of the law of grave breaches. No new grave breach was born outside of the Geneva Conventions and AP I, in stark contrast with the continued recognition of new war crimes from out of Article 3 common to the four Conventions (common Article 3).Footnote 253
Second, while the regime of “grave breaches” may have been a disappointment to those with greater normative ambitions, it came to be accepted by all as a common core of criminal prohibitions – though rarely enforcedFootnote 254 – that are recognized by customary international law.Footnote 255
Third, the Geneva Conventions in effect validated the course of action taken at Nuremberg and Tokyo by making it clear that the war crimes for which Axis leaders had been prosecuted were crimes not just for those prosecuted after the Second World War but for everyone. This helped address, to an extent, the claim that the law which was applied to convict these individuals had been made to fit their crimes.
Fourth, out of a seemingly modest normative root, common Article 3 grew an entire regime of war crimes applicable to non-international armed conflicts. Few observers would have recognized at the time of the 1949 Conventions’ adoption that this provision would become the source of such a regime, demonstrating perhaps the capacity of IHL to adapt and grow in order to fulfil its protective goals and to guarantee its own relevance and effectiveness.
The 1977 Additional Protocols to the Geneva Conventions contributed only modestly to the law of war crimes. AP I added a number of “grave breaches” to the existing list, including some pertaining to the conduct of hostilities.Footnote 256 AP I also made it clear that “grave breaches” were bona fide war crimes,Footnote 257 but did little to improve on the inadequacies of the regime of enforcement of such breaches.Footnote 258 However, AP I did add two provisions – Articles 86 and 87 – that would help to consolidate the doctrine of command or superior responsibilityFootnote 259 and to constrain yet further the lawful usage of reprisals as a means of enforcement of the laws of war.Footnote 260 As for non-international armed conflicts, Additional Protocol II (AP II) failed entirely to criminalize conduct in breach of its terms.Footnote 261 The reluctance of States to criminalize conduct occurring in a non-international armed conflict was apparent not just from the absence of such provisions in AP II, but also from the scope of criminalization of certain offences in AP I.Footnote 262
The work of the International Law Commission
Pursuant to Resolution 177(II) of 1947, the International Law Commission (ILC) was tasked by the UN General Assembly with drawing up the main legal principles to come out of the Nuremberg process.Footnote 263 As far as the law of war crimes was concerned, this effort added little to the body of existing law. Principle VI of the Principles of International Law Recognized in the Charter of the Nürnberg Tribunal and in the Judgment of the Tribunal (Nuremberg Principles) reiterated the content of Article 6(b) of the Nuremberg Charter, suggesting that the IMT had been correct when taking the view that the war crimes listed in the Charter were crimes under international law.Footnote 264 More pertinent was the reiteration by the ILC that “[a]ny person who commits an act which constitutes a crime under international law is responsible therefor and liable to punishment” (Principle I) and that the person’s position (including as head of State) (Principle III), their domestic laws (Principle II) or an order given (Principle IV) had in principle no bearing upon their responsibility for the commission of such acts.Footnote 265
In parallel, the ILC was mandated with preparing a draft code of offences against the peace and security of mankind, “indicating clearly the place to be accorded to the [Nuremberg] principles”.Footnote 266 This process, which eventually resulted in the adoption in 1996 of a Draft Code of Crimes against the Peace and Security of Mankind (Draft Code),Footnote 267 turned out to be a disappointment as far as the law of war crimes is concerned.Footnote 268 The Draft Code provided for various categories of war crimes, some inherited from the grave breaches regime of the Geneva Conventions, some from common Article 3 and Additional Protocols I and II, and some being generic violations of the laws and customs of war.Footnote 269 The Draft Code did not provide for an exhaustive list of war crimes, nor did it seek to define any of them,Footnote 270 but it did expand the list of recognized categories of war crimes and include a series of war crimes applicable to non-international armed conflict, thereby preparing the ground for the formal recognition of these war crimes in the Tadić case and in the statutory instruments of a number of international war crimes tribunals.Footnote 271
For the most part, the ILC Draft Code left the law of war crimes the way it had found it: as a work in progress. The Code remained principally aspirational in character, with sporadic references being made to it in the jurisprudence of international(ized) criminal tribunals as an illustration of the evolution and mainstreaming of some of the crimes it contained.Footnote 272 It also provided an inspiration for what would eventually become Article 8 of the Rome Statute of the ICC.Footnote 273 In particular, the terms of the Draft Code presaged the expression in the Rome Statute of a particular jurisdictional preference for war crimes committed on a broader scale; the Code’s reference to “when committed in a systematic manner or on a large scale” was replaced in the Rome Statute, however, by the milder and non-compulsory expression “in particular when committed as part of a plan or policy or as part of a large-scale commission of such crimes”.Footnote 274
A temps mort in the development of the law of war crimes
As far as the law of war crimes is concerned, the period from the 1950s to the early 1990s was very much a temps mort – a time where little of any significance for that law happened. Prosecutions occasionally occurred but were insufficient to set a strong current in motion; academic literature showed some interest in the topic but remained at the margins of public debate; and while domestic legislations were slowly integrating the idea of war crimes, in particular on the back of the “grave breaches” provisions of the Geneva Conventions, enforcement remained spotty and symbolic.Footnote 275 At the same time, international human rights law helped shape a normative minimum of legal protection that should be guaranteed to anyone in all circumstances, including war. In so doing, it prepared the ground for the erosion of the distinction between international and non-international armed conflicts when it comes to serious violations of IHL and made the forthcoming Tadić revolution a little more palatable to States.Footnote 276
The ad hoc tribunals
Statutory instruments
The ad hoc International Criminal Tribunal for the former Yugoslavia (ICTY) and International Criminal Tribunal for Rwanda (ICTR) marked a qualitative leap in the development of the law of war crimes. These jurisdictions served four principal functions in respect of that law: (1) as means of enforcement in respect of war crimes; (2) as clarifiers of the law; and as normative venues that helped (3) dust off and expand the reach of that law, as well as (4) giving greater protection for persons of concern to the laws of war.
The Statute of the ICTY provided for two categories of war crimes. Article 2 set out an (exhaustive) list of grave breaches, all of which were taken verbatim from the 1949 Geneva Conventions;Footnote 277 absent from the list were the other categories of grave breaches foreseen in AP I.Footnote 278 This provision was supplemented by Article 3 of the Statute (“Violations of the Laws or Customs of War”), which listed five other, non-exhaustive categories of war crimes.Footnote 279 This second provision made it clear that grave breaches of the Geneva Conventions were only one of several categories of war crimes recognized under international law. Article 3 was initially thought to capture only criminalized violations of the Hague law,Footnote 280 though the jurisprudence took it far beyond this and interpreted it, instead, as a residual clause to capture and bring within the ICTY’s jurisdiction a series of other criminalized violations of the laws of war, includingFootnote 281 (1) serious violations of the Hague law applicable to international and/or non-international armed conflicts; (2) serious infringements of provisions of the Geneva Conventions other than those classified as “grave breaches” by those Conventions; (3) serious violations of common Article 3 and other customary rules applicable to non-international armed conflicts; and (4) serious violations of Additional Protocols I and II.Footnote 282 In particular, it is from this statutory provision that the law of war crimes applicable to non-international armed conflicts would grow, first at the ICTY and then beyond its jurisdictional borders.Footnote 283
The jurisdiction of the ICTR was crafted differently in relation to war crimes. The ICTR Statute provided for the Tribunal’s jurisdiction over one sort of war crimes only, described as “[v]iolations of Article 3 Common to the Geneva Conventions and of Additional Protocol II” and consisting of eight non-exhaustive subcategories of war crimes,Footnote 284 including one that criminalized “threats” to commit a war crime.Footnote 285 This particular and more limited jurisdictional competence was the consequence of the view taken during the establishment of the ICTR that the armed conflict that had taken place in Rwanda during the relevant time period was non-international in character.Footnote 286 The ICTR Statute also made explicit what Tadić would confirm judicially a year later – namely, that serious violations of common Article 3 are crimes under international law.Footnote 287
Perhaps more important than the list of crimes foreseen in these statutory instruments was the fact that the two tribunals took the view that those offences – and other categories of war crimes read into the statutes – formed part of customary international law.Footnote 288 This was a way for the tribunals to demonstrate their attachment to the principle of legality: crimes existed under customary law at the time of the events so that the law of the statutes was not post facto law, but merely a written acknowledgment of pre-existing prohibitions applicable – as international law – to those concerned. It was of no consequence, therefore, that some of those might not have been foreseen by domestic law. The view that these were customary law crimes and not just the law of the ad hoc tribunals was also essential to making the tribunals’ jurisprudential pronouncements universal in character and relevance. This would play a significant part in shaping the list of war crimes that would come to be recognized in the Rome Statute of the ICC.
As already noted, the contributions of the ICTY and ICTR to the law of war crimes are at least fourfold: first, in terms of enforcement of these offences; second, through the jurisprudential refinement of definitions of many categories of war crimes; third, by expanding the reach of the law, ratione loci, materiae and personae (and perhaps even temporis), and thus multiplying the cases and situations subject to normative limitations; and fourth, as part of this, by furthering and accelerating the process of humanization of the laws of war – i.e., by placing greater weight on humanitarian concerns and less on countervailing considerations of military necessity when interpreting the underlying principles emanating from the laws and customs of war. Each of these four aspects will be considered in turn below.
Enforcement
While the law of war crimes had a somewhat long history of enforcement, the ad hoc tribunals signified a new era of accountability. Here were two temporary but functional international criminal tribunals with time and resources to investigate and prosecute widespread war criminality. The range of cases – in magnitude, nature, individuals involved, and types of violations of humanitarian law – was a clear illustration of the prosecutorial potential of the law of war crimes. Instances of ethnic cleansing (e.g., Karadžić, Prlić et al. and Milutinović et al.), sexual violence (e.g., Kunarac et al.), detention-related crimes (e.g., Kvočka et al. and Krnojelac), attacks on civilians and civilian objects (e.g., Strugar, Galić and Dragomir Milošević), and killings (e.g., Popović et al., Krstić, Vasiljević and Lukić and Lukić) were thus prosecuted under the umbrella of, inter alia, the law of war crimes.
This broad and forceful enforcement of the laws of war on behalf of the international community epitomized the deep erosion of the principle of absolute State sovereignty in respect of the enforcement of criminal law. First, the primary responsibility over the prosecution of these crimes was taken away from the relevant territorial States and jurisdictional primacy was handed over to the tribunals.Footnote 289 This was perhaps most significant in respect of war crimes committed in non-international armed conflicts, which until then had been understood to stand within the exclusive or at least primary jurisdictional boundaries of States. Second, the individuals of concern to these jurisdictions were not only those at the front lines of war criminality but included, as a priority, the planners and masterminds, who were the symbols and instruments of sovereign States. This resulted in the prosecution and conviction for war crimes of former presidents, ministers and generals.Footnote 290 New modes of liability were being created, and older ones refined and expanded to account for and capture the variety of ways in which one could participate in the commission of such crimes.Footnote 291 At the same time, the law continued to narrow down the circle of excuses and defences that could provide a valid exception to liability. At Nuremberg, the excuse of superior orders had been taken away as a defence;Footnote 292 before the ad hoc tribunals, immunities from prosecution were inapplicable, while the scope of application of certain defences (duress, intoxication, mistakes of law and fact) was narrowed down significantly. Most of the privileges that once attached to men in high offices were now gone, thereby keeping a promise first made in the aftermath of the First World War – namely, that anyone could in principle be held accountable for partaking in the commission of international crimes.
The law of war crimes developed by these jurisdictions also ventured into areas traditionally subject to much judicial deference, particularly in respect of the conduct of hostilities. The ICTY suggested, for instance, that reprisals were no longer a valid means of enforcement of the laws of war, or were at least a much reduced one.Footnote 293 It also held that military attacks which fall individually into the grey area between lawfulness and unlawfulness could be regarded by a tribunal to be unlawful as a whole through the cumulative effect of individual incidents of hostile acts of questionable legality.Footnote 294 The same tribunal looked critically into a party’s choice of weapons,Footnote 295 the protection of cultural objects,Footnote 296 and the manner of conducting offensive military operations;Footnote 297 it set out a whole range of steps and measures that military commanders would be expected to take as a precaution before launching an attack where civilians are present at or near the site of a military operation or planned attack;Footnote 298 and it criminalized acts committed not just against enemy fighters or civilians, but also against members of a party’s own forces.Footnote 299
The active enforcement of the laws of war by the ad hoc tribunals, and in particular by the ICTY, also contributed to the creation of the necessary momentum for the establishment of the ICC and the drawing up of a wide jurisdictional competence for this Court over war crimes.Footnote 300 Furthermore, the investigative and prosecutorial work of these jurisdictions sent a clear message that for those still hoping to evade justice when committing war crimes, room for impunity was becoming increasingly narrow and means of accountability increasingly sharp.
Defining
A second significant contribution of the ad hoc tribunals to the development of the law of war crimes consists of their efforts to define, clarify and bring a degree of certainty to the elements of various categories of war crimes within their jurisdiction.
Many of the war crimes recognized as such since the First World War had lived as normative beings for almost a century without any clear understanding of their definition and elements. The ICTY, and to a lesser extent the ICTR, would prove to be extraordinary interpreters and perhaps also part-legislators of many of these offences’ definitions. The tribunals not only defined a whole range of war crimes – from “outrages upon personal dignity” to unlawful attacks on civilians – but also set out the normative prerequisites for their application, such as (1) what amounts to an “armed conflict”, (2) what factual circumstances amount to a situation of occupation, (3) what the “nexus” requirement implies and requires, and (iv) what categories of individuals and properties are protected under different branches of the laws of war and what sort of acts or attacks carried out against them can constitute a war crime. They also clarified the conditions – ratione loci, temporis and personae – for the applicability of the laws of war and a variety of notions built into those laws, including proportionality, precaution, discrimination, protected persons and active participation in hostilities. Finally, the jurisprudential efforts that these tribunals put into defining the crimes within their jurisdictions also provided for a better and clearer understanding of the interaction and overlap that exist between, on the one hand, war crimes and, on the other, other categories of international crimes, particularly crimes against humanity and genocide.Footnote 301
Expanding
The jurisprudential activity of the ad hoc tribunals was strongly coloured by humanitarian considerations and did not merely build upon existing structures. Here were judges, restricted only by a general framework of statutory law, with the responsibility of dusting off and enforcing a rather powerful but unsophisticated body of prohibitions. The combination of the many normative uncertainties affecting this body of law, creative spirits on the bench, and the sheer horror of the crimes being punished legitimized a certain amount of jurisprudential creativity on the part of these jurisdictions, resulting in a broadening of the law’s reach and protective effect.
For a start, the ICTY defined the notion of “armed conflict” – the prerequisite for the applicability of the laws of war and a precondition for the possibility of war crimes – quite expansively.Footnote 302 Under its definition, any resort to armed force between States would constitute an international armed conflict,Footnote 303 while protracted armed violence between governmental authorities and organized armed groups, or between such groups within a State, would constitute a non-international armed conflict.Footnote 304 By setting a low(-ish) threshold to determine what situations would constitute an “armed conflict”, the ad hoc tribunals broadened the scope of situations that would come to be regulated by the laws of war and thus expanded the range of circumstances in which war crimes could be committed. Ratione temporis, the notion of “armed conflict” was also drawn up broadly,Footnote 305 being made to capture both the early stages of hostilities and the tail end of them in order to ensure that IHL comes into play and remains relevant until the point when there is no longer any need for it.
The second way in which the ad hoc tribunals expanded the reach of the law of war crimes was perhaps even more remarkable. Up until the mid-1990s, there was a quiet and conservative consensus that war crimes only existed, normatively speaking, in the context of international armed conflicts.Footnote 306 This consensus was shattered once and for all by a single decision of the Appeals Chamber of ICTY, presided by Judge Antonio Cassese. The Tadić Jurisdiction Decision all but buried that view and turned it into an obsolete, almost absurd, thing of the past; from that point onwards, there was little question that war crimes could be committed not only in international armed conflicts (including situations amounting to an occupation) but also in non-international armed conflicts.Footnote 307 From the recognition of that fundamental principle, there was only one more step, enthusiastically taken by the ad hoc tribunals, to start outlining a whole range of war crimes that were said to be of relevance to this sort of conflict, including serious violations of common Article 3Footnote 308 as well as serious violations of AP II.Footnote 309 The resulting body of law grew steadily to a point where the range of war crimes relevant to non-international armed conflicts now closely resembles those applicable to international conflicts.Footnote 310
Third, the law that came out of these jurisdictions was also expanded ratione personae. In relation to potential victims, the law of war crimes was interpreted as encompassing categories of individuals that until then might have been thought to fall outside of it. For instance, under the ad hoc tribunals’ jurisprudence, members of a party’s own forces,Footnote 311 fellow nationals,Footnote 312 individuals listed as reservists in the perpetrators’ forces,Footnote 313 members of allied forces or co-belligerents,Footnote 314 or the personnel of UN missions – even if they used force (in self-defence) against the perpetrators – could all in theory be victims of a war crime.Footnote 315 The notion of “protected person”, which determines whether an individual can be the victim of a grave breach of the Geneva Conventions and which was once reserved for those who carried a different nationality than the perpetrator, was according to the ICTY also applicable to those whose “allegiance” was different to that of the perpetrator even though they might carry the same passport as their victimizer.Footnote 316 Similarly, the concept of “active participation in hostilities”, which is central to the question of protection under the laws of war, has been interpreted by the ICTY quite narrowly, so that only those whose actions are clearly and materially connected to the prosecution of hostilities would lose their protection as civilians under the laws of war.Footnote 317
Humanizing
The contribution of the ad hoc tribunals to the law of war crimes was not limited to expanding its reach and better defining its contours. These jurisdictions also changed the very texture of many parts of that law by resetting the equilibrium built into the laws of war between humanitarian considerations and military necessity, often in favour of the former.
The expansion of the scope of application of the laws of war was itself humanizing: by defining the notion of “armed conflict” broadly, the application of the laws of war was triggered in many situations which until then might have been thought to escape the protective edge of the law. Furthermore, the level of acceptable violence in war was normatively pushed downwards by the jurisprudence of these tribunals. Practices once tolerated as legitimate methods of war, such as reprisals, starvation, recruitment and use of child soldiers, use of indiscriminate weapons, and the creation of a humanitarian crisis as a means of displacement of the population, were all prohibited or heavily constrained by the laws of war and criminalized by the law of war crimes. Following Tadić, conduct considered to be inhumane and therefore criminal in international armed conflicts was clearly considered to be also inhumane and criminal in the context of non-international armed conflicts.Footnote 318 In this way, the ICTY effectively declared that there was no greater acceptance of gratuitous violence in non-international armed conflicts than there was in the international sort.
The Rome Statute and beyond
The adoption in 1998 of the Rome Statute of the ICC was an important codificatory moment in respect of all international core crimes, in particular the law of war crimes.Footnote 319 This was an instrument that was taking stock of decades of normative developments and refinement, a great deal of which had taken place jurisprudentially outside of States’ control and with limited input on their part. The text is, however, not purely codifying in nature but constitutes a mixture of normative accounting, novelties and retractions. On the one hand, it sticks more closely than the jurisprudence of the ad hoc tribunals to the normative root (IHL) of the recognized categories of war crimes. For instance, since at least the First World War, customary international law has criminalized as a war crime the act of “wanton destruction of cities, towns or villages, or devastation not justified by military necessity”.Footnote 320 Such an offence does not expressly feature in the Rome Statute; instead, one finds two distinct offences that re-anchor this general prohibition in IHL, narrow its scope, and subject proof of its commission to the verification of a variety of conditions set out in the laws of war.Footnote 321 On the other hand, the Rome Statute also takes on board much of the jurisprudential developments recorded before the Yugoslav and Rwanda tribunals, in particular a wide range of war crimes relevant to non-international armed conflicts,Footnote 322 and includes in its catalogue of offences a series of gender-based and sexual offences that had earlier fallen into broader, non-descriptive categories.Footnote 323
The Rome Statute is thus only a partial, non-exhaustive accounting of the law of war crimes, and one which is not fully aligned with that law. For instance, the war crime of murder is not part of the ICC’s jurisdiction, and neither are the war crimes of slavery/enslavement, unlawful or forced labour, terror, arbitrary detention or collective punishment – all of them recognized categories of war crimes under customary law. Furthermore, the definitions of several categories of war crimes under the Rome Statute differ from their customary law counterparts.Footnote 324 For instance, Article 8(2)(b)(iv) provides for the war crime of
[i]ntentionally launching an attack in the knowledge that such attack will cause incidental loss of life or injury to civilians or damage to civilian objects or widespread, long-term and severe damage to the natural environment which would be clearly excessive in relation to the concrete and direct overall military advantage anticipated.Footnote 325
The requirement of the damaging effect being “clearly excessive” is not mentioned in the Geneva Conventions or their Additional Protocols and does not form part of customary law.Footnote 326 Customary law also recognizes offences of “plunder of public or private property”; in contrast, the Rome Statute provides for the narrower notion of “[p]illaging a town or place, even when taken by assault”, which thus restricts the sort of unlawful acquisition of property over which the ICC has jurisdiction.Footnote 327 As a result, the regime of war crimes applicable before the ICC can be said to be generally grounded in existing customary law, but it also departs from it in several ways.Footnote 328
Importantly, the Rome Statute became a normative pivot for subsequent domestic and international texts on international crimes. Not only did it inspire many domestic implementing legislations, but it also served as a starting point for drawing up the statutory instruments of other international(ized) criminal jurisdictions, although some of these departed from the ICC regime.Footnote 329
In the broader picture of a history of war crimes, the Rome Statute of the ICC is therefore both a long step forward and a short step back. For it not to stunt the continued development of the law, it will be important that the Court and those making use of the ICC regime do not freeze the law in time and that they consider it for what it represents – namely, a partial and incomplete work of codification tailored to the needs and specificities of this particular jurisdiction.
Hybrid, internationalized and domestic jurisdictions have made similarly important contributions to the clarification and development of the law of war crimes. For instance, domestic courts have read into common Article 3’s guarantee of “humane treatment” a war crime of “arbitrary detention”.Footnote 330 They have also confirmed that, ratione loci, war crimes can be committed not just on the territory of the State in which an armed conflict is taking place, but also on the territory of a neighbouring State into which the conflict has, normatively speaking, spilled over.Footnote 331 For their part, the Special Court for Sierra Leone and the Extraordinary Chambers in the Courts of Cambodia have clarified and developed the law applicable to a variety of war crimes, including those involving sexual violence, terror, collective punishment, the recruitment and use of child soldiers, and the wilful deprivation of fair trial rights to prisoners of war; as part of that jurisprudential process, they have helped to iron out some of the normative differences between the regime of war crimes applicable to international and non-international armed conflicts.Footnote 332 Collectively, hybrid, internationalized and domestic courts have also contributed to clarifying the nature and scope of obligations binding upon non-State armed groups and their leadership, in particular in respect of ensuring compliance with IHL and sanctioning violations of that law attributable to their members.
The last important contemporary piece of the law of war crimes is to be found in the ICRC’s Customary Law Study.Footnote 333 In this document, through a careful study of the practice of States, international jurisprudence and international instruments, the ICRC has drawn up a detailed accounting of customary IHL. Among the rules which it has found to form part of customary international law are a series of principles and prohibitions that form part of the law of war crimes: the principle of individual responsibility embedded in the law of war crimes (Rule 151), including the principle of command responsibility (Rules 152–153); the exclusion of superior orders as a defence (Rules 154–155); the definition and categories of war crimes recognized under customary international law (Rule 156); jurisdictional and prosecutorial principles relevant to the prosecution of war crimes (Rules 157–158); and rules on amnesty (Rule 159), statutes of limitations (Rule 160) and international cooperation (Rule 161). Like the Rome Statute, the ICRC Customary Law Study serves an important function of crystallization, clarification and undeniability of the State of the law that regulates war crimes, in particular in respect of war criminality in non-international armed conflicts.
Conclusions
The notion of war crimes is the point at which IHL meets international criminal law. At their core, war crimes are the reflection of a subset of particularly important prohibitions forming part of IHL, such as the prohibitions on attacking civilians who are not or are no longer directly participating in hostilities, on forcible displacement and on inhumane treatment. On top of these prohibitions, international law has built an additional layer of criminal law pursuant to which an individual who violates these core humanitarian guarantees can engage his or her individual criminal responsibility as a direct result of international law.
The idea that international law regulates warfare and that some of its breaches are crimes under international law took centuries to be accepted and to take definite normative shape. First, various currents of law – Roman, canon and natural law; principles of chivalry; military customs; domestic military codes and regulations; international humanitarian conventions – converged to create an initial block of rules and prohibitions accepted as binding by those fighting wars. These came to be known as the laws and customs of war, and they were understood to provide a basic though important core of humanitarian rules and principles that enabled warring parties to conduct the business of war with one eye on humanitarian considerations and the other on practical, economic and military matters.
Once this modest basis of yet-to-be-named humanitarian law came to be accepted, it required some sort of enforcement system to give it an element of compulsion and to build in a degree of accountability in respect of its violators. Over the course of time, a variety of means – ransom, financial reparations, reprisals, hostage-takingFootnote 334 – were tried in order to give the laws of war an element of sanction and compulsion. Their evident limitations as means of enforcement of the laws of war helped to make the case for a more potent response to breaches of IHL – namely, the idea of individual criminal responsibility.Footnote 335
This idea came to be associated with a number of core prohibitions that formed part of the nascent body of law, in particular the prohibitions against pillage and plunder; attacks on churches and religious personnel; rape, abduction and abuse of women and children; attacks on the wounded and the sick; mistreatment of prisoners; attacks on civilians, medical personnel and undefended places; deportation and internment of civilians in inhuman conditions; and forced labour, along with a variety of other grave violations of core features of the laws and customs of war.Footnote 336 By recognizing that the commission of any of these acts could engage the responsibility of its perpetrator, a new mechanism of enforcement was built into the laws of war which looked beyond the parties to the conflict and directly at those fighting on their behalf and who engage in such conduct.Footnote 337 By the end of the First World War, it was generally accepted that an individual who violates the laws of war could engage his or her criminal responsibility not just as a result of domestic criminal law but of international law itself.Footnote 338
The recognition of the principle that individuals are answerable to international law for certain violations of the laws of war came with new elements of enforcement. As the idea of individual criminal responsibility was taking shape in respect of such acts, the jurisdictional principle that all belligerents are permitted to try those who breach the laws of war became uncontroversial and part of customary international law.Footnote 339 The notion of war crimes was therefore a recognition not just that certain violations of international law are criminalized by international law, but also that international law endows all belligerents with the competence and jurisdiction to punish such acts. Further, from the reflections of Moynier and the work of the Institute of International Law, the idea grew that punishment for such acts should not be contingent on the will or ability of any single State. International or internationalized jurisdictions were being imagined to prosecute those who, like the Kaiser, had trampled upon the collective interests of the international community. These jurisdictional developments reflected the view that the laws of war were not just the concern of the belligerents but were general prohibitions that protected collective interests and were made binding on all by international law.
These developments broke a number of taboos. One was that individuals and not just States are subject to international law, and part of that law that was binding on individuals is penal in character, so that its breach could engage the responsibility of a culpable individual as a direct result of the operation of international law and irrespective of domestic law. Broken, too, was the taboo of exclusive jurisdictional competence of States. In Versailles, the Allied powers had set out a general – and highly inadequate – architecture for an international sort of judicial mechanism, which never came into being. At Nuremberg, however, Moynier’s dream of an international court became a reality in the form of the IMT and set a model for later such endeavours. These developments made it increasingly clear that the prohibition and prosecution of war crimes was in effect the enforcement of a collective good that one nation, or group of nations, could not deny all others.
Together with these seismic changes came a number of perhaps more modest but no less important normative developments. First, the law of war crimes was soon to become “universal” in character (or close to it), with jurisdictional principles to match. Conventions were adopted by relevant powers, and international customs were developing that were increasingly regarded as applicable to all. The 1919 list of war crimes was an early reflection of that new reality: it contained thirty-two different categories of conduct that were crimes for any and all individuals, irrespective of status, rank or nationality.
Second, over time, the law regulating war criminality was becoming more sophisticated and more expansive in its reach. From modest beginnings, it came to regulate several core elements of warfare: weaponry; persons deprived of their liberty; means and methods of warfare; the treatment of local populations; the use and appropriation of enemy property; occupation of another State’s territory; and a variety of other important aspects pertaining to the conduct of hostilities. The list of conduct recognized as criminal under the laws of war also became broader and more specific.
Less explicit perhaps, but equally relevant to the development of the notion of war crimes, was the fading away of exceptions to the principle of individual responsibility for serious violations of the laws of war. This was apparent, for instance, from the shrinking tolerance of amnesties in respect of acts amounting to war crimes,Footnote 340 the increasingly restrictive possibility of lawful reprisals, ever more demanding obligations placed upon military commanders in respect of the conduct of their subordinates, and the narrowing discretion of military men in the way they could conduct hostilities. All of these developments highlighted one common normative reality: there was a growing belief that individuals and not just States were responsible for the manner in which war was being carried out, and that those who disregarded the limitations that the laws of war placed upon the conduct of warfare should be held to account for doing so.
That first long era in the life of the law of war crimes came to an end with the Second World War. It had been a time of important developments, but also a time of arrested development. There was still resistance to this new international criminal law amongst some States, which considered that it was encroaching too far and too fast into their sovereignties.Footnote 341 Concerns for State sovereignty were in full view, for instance, in the dissenting reports of the American and Japanese delegations on the Commission of Responsibilities. They were also apparent from the absence of provisions on war crimes in international treaties from that era and from the reticence of States to create supranational mechanisms of enforcement for the laws of war. And what was considered to be law at that point in time would soon show its total inadequacy in the face of criminality the likes of which had never been witnessed before.Footnote 342
The events and criminality of the Second World War would turbo-charge the development of the law of international crimes and the law of war crimes in particular. At the core of those developments stood the realization that international law lagged far behind the criminality that this conflict had witnessed. New law and new mechanisms of enforcement were therefore needed, so new law was made (relating, for instance, to crimes against humanity and crimes against peace), old law was brought up to date (war crimes), exceptions to liability (such as immunities and superior orders) were set aside, and a new architecture was devised, consisting of a body of international criminal law that would stand above domestic laws, focused on the responsibility of individuals, regardless of rank or status, and with an international(ized) structure to serve as its enforcer.Footnote 343 The setting up of the IMT for the trial of war criminals whose offences had no particular geographical location was critical to that new legal environment.
By enforcing these new legal standards, the Nuremberg Tribunal helped to crystallize and shape the law of war crimes and triggered many of the later developments of that body of law.Footnote 344 First, the Tribunal recognized that the laws of war were constituted not just of treaties but also of customary law – i.e., law binding on all regardless of adhesion to a treaty and regardless of any “general participation” clause. At Nuremberg, the Hague and Geneva law, as then existed, thus effectively gained universal status and relevance. Second, the laws of war applied at Nuremberg were evidently brought up to date in order for them to meet the demands of the day: they were said, for instance, to apply in occupation regardless of any claim of annexation; superior orders were de-recognized as a defence against charges involving allegations of violations of international law;Footnote 345 the application ratione personae of the laws of war was also expanded, in respect of both perpetrators and victims;Footnote 346 and some of the core prohibitions of these laws were criminalized so that individuals participating in such acts could be punished for doing so.Footnote 347 The expansive criminalization of violations of the laws of war was also a clear indication of the growing awareness of the shortcomings of traditional means of enforcement of the laws of war – including reprisals, hostage-taking and third-party complaint mechanismsFootnote 348 – in terms of deterrence, retribution and accountability.Footnote 349
This process of criminalization of the laws of war involved the erosion of State sovereignties in relation to one of their core attributes – namely, the application of criminal law and associated punishment. It also signified that while war was still a business primarily between States, those acting on their behalf could lose the benefit of their national laws, and other defences associated with their status and position, if they engaged in conduct regarded as amounting to war crimes. As a result, individual criminal responsibility now very much ran parallel to the notion of State responsibility.
The next phase of development of the law of war crimes was one of partial codification of previous developments. The 1949 Geneva Conventions and their 1977 Additional Protocols clarified and updated the laws of war in many ways, making it clear that a great deal of what had been authorized (or at least not prohibited) before the Second World War was now regarded as unlawful. The regime of “grave breaches” also provided for a number of legal obligations binding on States (to investigate, to prosecute or extradite, to exercise universal jurisdiction) that were intended to render the system of enforcement of the law of war crimes more effective. The Geneva Conventions further drew up or highlighted new normative distinctions – such as between international and non-international armed conflicts, between grave breaches and other categories of breaches of the Conventions, between “protected persons” and other categories of people enjoying the protection of IHL, and between prisoners of war and other sorts of detained persons – that the law of war crimes would in turn have to build into its own architecture. This rendered what had up to that point been a rather simple and straightforward body of penal prohibitions into something more compartmentalized and unwieldy.
As soon as the law of war crimes went back into the hands of judicial institutions, judges – in particular, those of the ICTY and ICTR – spent a good deal of time ironing out and neutralizing some of the normative subtleties that were born of the Geneva Conventions. The hard line drawn in the Conventions between international and non-international armed conflicts, while still relevant, was rendered a lot less important by the judicial recognition of a universe of war crimes applicable to the latter sort of armed conflicts. Similarly, the notion of “protected persons” built into the Geneva Conventions, which differentiated between people on the ground of nationality, was judicially diluted into a test that focuses on the question of allegiance and legal protection of those concerned under the laws of war. Furthermore, the rather constricted regime of “grave breaches” foreseen by the Geneva Conventions was rendered all but secondary through the development of a much broader regime of war crimes that applies to all categories of armed conflicts, generally ignores questions of nationality or allegiance, and covers a much broader set of protected interests. The law of war crimes as it came out of the combined jurisprudence of the ICTY and ICTR was also a great deal more specific, more encompassing and more focused on humanitarian considerations than it had been when it entered the pipeline of those jurisdictions. Finally, the Rome Statute and the ICRC Customary Law Study provide a snapshot – albeit a momentary and partial one – of what the refreshed law of war crimes looked like at the turn of the last century.
Today, the greatest challenge facing the law of war crimes is not about its normative contours; rather, it is one of effective enforcement, and a rather painful lesson of history is that enforcement has generally come only after cataclysmic events. There is, however, a more optimistic reading of history – one where States are reminded of the fact that they created and committed to certain minima of legal protection for all those affected by war not as an expression of their individual interests, but as a recognition of their shared humanity. In that context, the timely and effective prosecution of war criminals is not to be understood as purely or even primarily punitive in character. It is a necessary element of the preservation of a common humanity, a reminder of the relevance of the law for those who engage in warfare, and a rare point of deterrence standing against the temptation of unrestricted violence and the sense of impunity that often fuels such violence.
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