A. Examination of relevant legal frameworks and their operational context

The obligation to rescue persons in distress at sea is widely recognized as a fundamental international norm, reflecting both longstanding maritime practice and core humanitarian principles.Footnote ⁶ State practice and opinio juris demonstrate broad acceptance that those imperilled at sea must be assisted, and this duty manifests across multiple legal regimes that apply in differing circumstances.Footnote ⁷ Although the concrete modalities of rescue vary with context, the underlying normative commitment – that human life at sea warrants priority protection – remains constant. Contemporary doctrine therefore treats maritime rescue as an ever-present obligation whose content is shaped by peacetime maritime laws as well as by the legal regime applicable in armed conflict.Footnote ⁸

In peacetime, maritime rescue operations are governed by international treaties, most notably Article 98 of the 1982 United Nations Convention on the Law of the Sea (UNCLOS),Footnote ⁹ which codifies the duty to save life at sea, in the absence of armed conflict. Article 98 imposes a dual obligation: flag States must ensure that shipmasters render assistance to persons in distress and proceed with all possible speed to their rescue, while coastal States are required to establish and maintain effective search-and-rescue services, including through regional cooperation where necessary. Although this article primarily addresses the obligations of States, the duty to render assistance applies to both States and shipmasters, and the obligations it contains are generally regarded as applicable to all ships, including warships.Footnote ¹⁰ In tandem with the general duty later codified in UNCLOS, the 1979 International Convention on Maritime Search and Rescue (1979 SAR Convention)Footnote ¹¹ provides a detailed framework for national and regional coordination. It establishes search-and-rescue regions, mandates the creation of rescue coordination centres, and standardizes procedures to ensure timely, effective, and cooperative responses to persons in distress at sea.Footnote ¹²

Whereas UNCLOS sets forth the overarching codification of the customary duty to render assistance, and the 1979 SAR Convention establishes procedural and regional coordination mechanisms, the 1974 International Convention for the Safety of Life at Sea (SOLAS)Footnote ¹³ serves as the most fundamental and authoritative international benchmark for maritime safety, contributing in practice to the prevention of maritime accidents by setting minimum safety standards for ships and maritime transport. Although SOLAS explicitly excludes warships, naval auxiliaries, and other government non-commercial vessels from its application,Footnote ¹⁴ such a limitation does not justify a narrow interpretation of the duty to rescue at sea as applying solely to merchant ships, given that the fundamental purpose of maritime rescue is to ensure the saving of human life at sea, a purpose that necessarily extends to all ships, including warships, during peacetime.Footnote ¹⁵

Indeed, this understanding is reinforced by the widespread State practice wherein numerous States explicitly mandate their sovereign immune vessels to render assistance at sea as a matter of national policy and military instructions, rather than as a de jure obligation arising from global maritime Conventions.Footnote ¹⁶ Furthermore, the 1989 Salvage Convention provides a legal framework for salvage operations, including the duty of masters to render assistance to persons in danger at sea; while it likewise excludes warships and other State-owned non-commercial vessels from its scope, it nonetheless permits States to extend the application of the Convention to such vessels at their discretion.Footnote ¹⁷ Taken together, these instruments define the core expectations of modern maritime rescue: prompt action, coordinated responses, and the availability and appropriate use of operational capabilities.

Even in situations of armed conflict at sea, the duty to rescue remains applicable. The humanitarian principle underlying this obligation was first enshrined in treaty form by the 1864 Geneva Convention,Footnote ¹⁸ which sought to protect wounded and sick members of armed forces; however, its scope of application was limited to warfare on land. This limitation was partially addressed by the Hague Convention III (1899), which extended the basic principles of the Geneva Convention to naval warfare and thereby introduced, for the first time at the treaty level, rules aimed at protecting victims of armed conflict at sea.Footnote ¹⁹ That Convention, however, confined itself to requiring military and civilian hospital ships to render assistance and relief, without distinction of nationality, to the wounded, sick, or shipwrecked,Footnote ²⁰ and did not expressly regulate the obligation of belligerents to conduct rescue activities in the course of hostilities, nor the broader duty to carry out rescue in connection with armed engagements.

These shortcomings were remedied with the adoption of the 1907 Hague Convention X, which provides that, after every engagement, belligerents must, so far as military interests permit, take measures to search for the shipwrecked, wounded, and sick, and to ensure their protection, as well as to safeguard the dead against pillage and ill-treatment.Footnote ²¹ These developments, drawing lessons from the devastating experience of naval warfare during the Second World War, ultimately led to the adoption of the Geneva Convention for the Amelioration of the Condition of Wounded, Sick and Shipwrecked Members of Armed Forces at Sea of 12 August 1949 (Second Geneva Convention),Footnote ²² which sought to further expand and strengthen humanitarian protections applicable during armed conflict at sea.

Within the law of armed conflict at sea, the Second Geneva Convention occupies a pre-eminent position because it specifically addresses the protection of the wounded, sick, and shipwrecked arising from naval hostilities and thereby translates the humanitarian core into concrete obligations for belligerents. Article 12 establishes the foundational protective standard: “Members of the armed forces and other persons … who are at sea and who are wounded, sick or shipwrecked, shall be respected and protected in all circumstances”, with “shipwreck” understood to include shipwreck from any cause and forced landings at sea by or from aircraft.Footnote ²³ The Article requires that “such persons shall be treated humanely and cared for by the Parties to the conflict in whose power they may be, without any adverse distinction founded on sex, race, nationality, religion, political opinions, or any other similar criteria.”Footnote ²⁴ This unequivocal nondiscrimination mandate implies that rescue and medical care are owed to all shipwrecked persons without discrimination, regardless of whether they are enemy, friendly, or neutral.

Article 18Footnote ²⁵ sets out the specific duty to conduct rescue operations following a naval engagement.Footnote ²⁶ Its operative language imposes two complementary standards: rescue efforts must be undertaken “without delay”, and Parties are required to take “all possible measures”Footnote ²⁷ to search for, collect, and protect the shipwrecked, wounded, and sick. The temporal phrase “without delay” sets an expectation of the prompt initiation of rescue activities once circumstances permit; the qualitative expression “all possible measures” establishes an obligation to employ the practicable means reasonably available under the prevailing operational conditions. The Article further requires that rescued persons be protected against pillage and ill-treatment and that their adequate care be ensured. In a separate paragraph, it also provides that, whenever circumstances permit, the Parties shall make local arrangements for the removal of the wounded and sick by sea and for the passage of necessary medical and religious personnel and equipment.

This treaty-based mandate is further reinforced by a consistent body of State practice, as evidenced by the military manuals of leading naval powers which align their operational guidelines with the Second Geneva Convention. For instance, the US Commander’s Handbook on the Law of Naval Operations and the UK Joint Service Manual of the Law of Armed Conflict both explicitly reaffirm the duty to take all possible measures without delay to search for and collect the shipwrecked after an engagement.Footnote ²⁸ Crucially, these manuals contextualize this obligation by conditioning it upon “military exigencies” or “consistency with their own security”, thereby demonstrating that major naval States view the rescue duty not as an inflexible absolute, but as a mandatory legal requirement to be implemented within the bounds of feasibility and force protection. Such State practice is consistently mirrored in the leading restatements of naval warfare law, notably the San Remo Manual (Rule 159) and the Newport Manual (Section 10.6). While the San Remo Manual establishes a fundamental link by mandating that its rules shall not depart from the detailed provisions of the Convention,Footnote ²⁹ the Newport Manual further clarifies that the Article 18 obligation is expected to be fulfilled insofar as military exigencies permit.Footnote ³⁰

This convergence of treaty law and State practice reinforces the broad consensus that the duty to rescue at sea constitutes an enduring norm applicable even in armed conflict. As the core embodiment of this norm, Article 12 solidifies the humanitarian bedrock of this duty by ensuring that neither hostile statusFootnote ³¹ nor any protected attributes negate the right to rescue and medical care. In practical terms, however, its implementation may involve a due account of military exigencies and the measures necessary to achieve legitimate military objectives. Nonetheless, the legal framework fundamentally demands that rescue actions be initiated swiftly and pursued with all feasible means – a balance codified in Article 18 through the combination of “without delay” and “all possible measures”. Building upon this operational consensus, the following section examines the substantive meaning of these two expressions, their interaction, and the inherent limitations in their application within contemporary naval warfare.

B. Conceptual analysis of key phrases: “without delay” vs. “all possible measures”

The phrase “without delay” emphasizes the temporal urgency of an obligation, but it does not denote an absolute requirement to commence rescue activities unconditionally upon the cessation of an engagement, irrespective of legitimate constraints. In this regard, the interpretation of the International Court of Justice (ICJ) in the Avena caseFootnote ³² provides an important point of reference. The ICJ clarified that “without delay” cannot be understood as requiring the immediate performance of a particular act following any specific point in timeFootnote ³³; rather, where the treaty itself does not define the term, its meaning must be derived from the context, object, and purpose of the treaty, as well as the relevant travaux préparatoires.Footnote ³⁴ This interpretative reasoning may be analogously applied to the post-engagement rescue obligation under the Second Geneva Convention, which seeks to reconcile humanitarian imperatives with operational exigencies. Accordingly, a good-faith interpretation of the ordinary meaning of “without delay” supports the view that a temporary delay in initiating rescue process may be justified where legitimate circumstances prevent prompt action in the immediate aftermath of an engagement.

This raises the question of what constitutes a justifiable delay in the rescue obligation following the cessation of an engagement under the Second Geneva Convention. In the Avena case, dozens of persons of Mexican nationality or origin faced criminal charges in the US, raising the question of whether their consular authorities were notified of their right to communicate with and to receive assistance from consular officers “without delay” under Article 36(1)(b)Footnote ³⁵ of the Vienna Convention on Consular Relations. The Court emphasized that compliance with the notification obligation must be assessed on a case-by-case basis, and the outcome may vary depending on the specific circumstances of each situation: in cases where foreign nationality was clearly established at the time of arrest, a 40-hour delay was considered a breach,Footnote ³⁶ whereas a delay of five days did not amount to a violation when nationality was initially uncertain.Footnote ³⁷ This illustrates that, in the context of obligations arising from international law, a temporary delay may be justified if reasonable grounds exist to prevent the immediate commencement of assistance measures. Ultimately, the determination of what constitutes a justifiable delay in the fulfilment of the post-engagement rescue obligation depends on the specific circumstances and constraints faced by the rescuing authorities, rather than on an absolute temporal standard.

The obligation to take “all possible measures” constitutes an obligation of conduct and entails the exercise of due diligence to achieve a specific objective.Footnote ³⁸ In its ordinary meaning, the term encompasses all measures that are practically feasible or attainable, implying that every effort must be undertaken under the prevailing circumstances to realize the purposes intended by the Convention. Thus, the term is inherently resolute both in its scope and in the manner of its implementation. In comparison, Article 16(1) of the 1907 Hague Convention XFootnote ³⁹ restricted the rescue obligation with the phrase “as far as military necessity permits”, thereby subordinating the duty to military objectives. Whereas Article 18 of the Second Geneva Convention replaced this formulation with “all possible measures”, it can be understood as broadening both the modalities and the scope of rescue obligations. Although military considerations remain relevant, this revised formulation reflects the contemporary expectation that all available measures be actively employed, in line with the era’s imperative for robust humanitarian considerations. Accordingly, the provision is not merely a matter of choice but constitutes a norm mandating an active duty to rescue after engagement.

In operational terms, “all possible measures” requires commanders to explore and deploy all available avenues to execute rescue missions effectively. In this regard, it is the Parties to the conflict who must determine what constitutes “possible measures” in each situation, guided by the principle of good faithFootnote ⁴⁰ and informed by their own established State practice.Footnote ⁴¹ In other words, the implementation of “all possible measures” presupposes not only the actions of the on-scene commander, but also the coordinated efforts of higher command and the broader operational structure, so that all feasible measures can in fact be carried out at a broader and systemic level. This understanding indicates that, even in the analysis of a single engagement, the post-engagement rescue obligation is not merely a delegated duty imposed on the on-scene commander alone. Rather, it constitutes a “package” obligation incumbent upon the Party State to the conflict, encompassing not only the conduct of hostilities itself but also the organization and execution of post-engagement rescue. Accordingly, such measures include not only the direct rescue efforts undertaken by the warship involved, but also the broader responsibility of the Party to maintain comprehensive situational awareness of the rescue theatre, to disseminate information on the location of the rescue, to identify and deploy the most appropriate rescue assets, and to assess and coordinate in real time what measures should be taken to effectuate rescue.Footnote ⁴² By way of illustration, if a submarine is unable to surface and conduct rescue after an attack – for instance, due to tactical reasons – the Party to the conflict must immediately assess alternative modes of rescue and take steps to identify and implement other feasible options capable of addressing the situation.Footnote ⁴³

Article 18 does not employ terms such as “immediately” or “forthwith”, but instead requires action “without delay”, nor does it mandate the taking of “all measures”, referring rather to “all possible measures”. These formulations reflect a deliberate normative design that presupposes the existence of practical and situational constraints, thereby avoiding the imposition of an obligation of absolute immediacy or the assumption of unlimited resources. Read in conjunction, these two standards define not only the substantive content of the post-engagement rescue obligation but also the analytical matrix within which compliance with Article 18 is to be assessed in practice. From that perspective, the combination of these two requirements structures the assessment of the timing of rescue and the manner in which they are to be conducted over time following an engagement. A temporary delay in initiating rescue activities, where justified by residual operational risks or objective constraints, may therefore be regarded as prima facie compatible with these requirements. However, as time passes and surrounding circumstances evolve, continued inaction may give rise to a presumptive violation, shifting the burden of justification to the Party concerned to demonstrate that the delay remained necessary and justifiable in light of prevailing risks and available alternatives.Footnote ⁴⁴

In short, these expressions reflect an effort to reconcile the imperative of prompt rescue with the practical realities inherent in post-engagement naval environments. While “without delay” emphasizes temporal promptness and “all possible measures” emphasizes the scope and intensity of effort, the two concepts are complementary. Together, they establish a dual framework for maritime rescue after an engagement that operates not as a rigid, momentary test but as a dynamic benchmark for legal assessment. Commanders are required to act swiftly when conditions permit and to maximize their efforts within feasible limits, implementing a practical balance between operational constraints and the humanitarian imperative. Integrating these two standards provides both procedural and substantive guidance, ensuring that the protection of human life at sea remains both effective and sensitive to field realities.

A. Operational constraints on immediate post-engagement rescue

In the period following an engagement, various factors – particularly considerations of military necessity – can make immediate rescue actions difficult. Maritime rescue after an engagement often occurs in an environment marked by lingering threats, including enemy vessels remaining in the area, intermittent or sporadic gunfire, or hostile aircraft that have just recently withdrawn after an attack,Footnote ⁴⁵ thereby creating an unstable and volatile situation for the Parties to the conflict. These conditions complicate the commanders’ decisions on whether to initiate search and rescue missions without delay. In addition, hidden threats, including submerged submarines, suspected mines, and undeclared missile threats, further strain the decision-making process and increase operational risk. Such dangers may remain undetected until the last moment, necessitating a cautious approach. Even after apparent residual threats have subsided, commanders must remain vigilant in anticipation of unforeseen hazards. Because the timing of such unpredictable threats cannot be determined in advance, precautionary periods may be prolonged, resulting in further delays to rescue efforts.

In practical terms, situations may also arise in which a ship’s performance or tactical environment is unsuitable for the prompt conduct of rescue. For surface ships, engine failures or damage from enemy fire can result in a loss of manoeuvring capability, while structural characteristics like high freeboards can make the recovery of survivors difficult even once the scene is reached.Footnote ⁴⁶ However, the most acute constraints often emerge from the inherent characteristics of submarines. Given that they are designed primarily for subsurface missions, surfacing to approach survivors entails fatal exposure to both sea and air threats. Maintaining stealth is a prerequisite for a submarine’s survival, and the risk of counter-detection in a contested environment often weighs heavily against a commander’s decision to initiate rescue efforts.Footnote ⁴⁷ A prominent precedent illustrating these constraints is the 1982 sinking of the ARA General Belgrano by the British submarine HMS Conqueror. Immediately following the torpedo attack, the submarine “withdrew at high speed” to evade potential counter-attacks and resumed offensive patrolling without surfacing to collect survivors.Footnote ⁴⁸ During the subsequent rescue efforts conducted by Argentine forces, the submarine refrained from attacking these assets, allowing the recovery of survivors to proceed without further interference.Footnote ⁴⁹ More recently, in March 2026, a US Navy fast-attack submarine torpedoed and sank the isolated Iranian frigate IRIS Dena within the exclusive economic zone of Sri Lanka in the Indian Ocean.Footnote ⁵⁰ Following the strike, the submarine avoided surfacing to collect survivors; instead, it alerted Sri Lankan authorities to the rescue location while maintaining its underwater stealth to fulfil its original military tasks.Footnote ⁵¹

Furthermore, commanders of the Parties to the conflict may face additional logistical constraints in the post-engagement phase. Fuel shortages may require resupply, and where no logistics support vessel is available in the vicinity, units may be compelled to forego immediate rescue and proceed to a port with refuelling facilities. Small warships alone are generally unsuitable for rescuing large numbers of persons due to their limited onboard accommodation, and therefore rescue must, in such cases, be conducted in coordination with nearby larger vessels. These limitations, arising from structural characteristics, may also apply to submarines involved in rescue efforts.Footnote ⁵² In addition, adverse weather conditions – such as severe storms – can significantly impede rescue missions, particularly for small warships that struggle to maintain stability. Where a typhoon is approaching, commanders may be required to seek shelter to ensure the vessel’s own safety rather than continue these activities. Collectively, these factors can create operational delays even when commanders are otherwise willing to conduct rescue immediately.

Reinforcing units deployed for rescue may, through misjudgment by the adversary, be subjected to unexpected treatment. This risk of misperception increases the likelihood of hostile fire directed at rescue assets, which is why naval commanders often hesitate to initiate immediate rescue in order to avoid unnecessary casualties. As an illustrative example, the 1942 Laconia incident highlights this concern. On 12 September 1942, in the South Atlantic off the coast of West Africa, U-156 torpedoed the British Royal Mail ship Laconia, which was carrying Italian prisoners of war, Allied soldiers, and civilians.Footnote ⁵³ Following the sinking, U-156 and supporting submarines towed lifeboats, provided medical care to the wounded, and displayed Red Cross flags to signal their humanitarian activities.Footnote ⁵⁴ Nevertheless, they were attacked by US B-24 bombers, resulting in numerous casualties among the survivors and damage to one of the submarines.Footnote ⁵⁵ In response, German Admiral Karl Dönitz, outraged by the exposure of his submarine crews to danger during the rescue, issued the so-called Laconia Order. The order essentially mandated the cessation of all efforts to rescue survivors of sunken ships, permitting rescue only for those who could provide information deemed strategically significant to the U-boat mission.Footnote ⁵⁶ This incident demonstrates that the rescue and evacuation of shipwrecked persons during or immediately after combat may be vulnerable to attack due to misidentification by adversaries.

A further concern is that these factors may arise simultaneously and in a layered manner. Residual armed threats, structural limitations, adverse weather conditions, and the risk of misidentification may operate cumulatively, compelling commanders to recognize that immediate rescue is not always feasible and to weigh the need for rescue against military imperatives. Such judgments are inevitably influenced by the commander’s situational awareness,Footnote ⁵⁷ an appreciation of acceptable levels of risk, and sensitivity to international humanitarian considerations. These factors may be understood as reflecting the distinct operational realities of naval warfare, and, in contrast to the First Geneva Convention,Footnote ⁵⁸ the fact that Article 18 of the Second Geneva Convention confines the obligation to rescue to the post-engagement phase may likewise be seen as stemming from the inherent peculiarities of armed conflict at sea.Footnote ⁵⁹ Taken together, these operational realities demonstrate that delay per se cannot be equated with non-compliance, provided that the commander remains engaged in continuous assessment and alternative rescue planning aimed at enabling rescue at the earliest feasible opportunity.

Viewed in this light, the operational constraints that impede immediate rescue may be understood, under the framework of the ILC Articles on State Responsibility, as grounds upon which the wrongfulness of a State’s omission may be precluded. First, when a commander delays rescue due to residual enemy threats – including the tactical vulnerability of submarines upon surfacing – or the grave risk of adversary misperception and subsequent attacks on rescue assets, the wrongfulness of the delay may be precluded under the principle of necessity.Footnote ⁶⁰ In these volatile scenarios, temporarily deferring can be an unavoidable measure to safeguard the State’s vital strategic assets and crew against an imminent and grave security peril. Second, a failure or delay caused by severe meteorological hazards can have its wrongfulness precluded under the concept of force majeure,Footnote ⁶¹ as an irresistible natural force like a typhoon renders the physical deployment of rescue assets or the rescue mission itself practically impossible. In contrast, logistical constraints such as inherent structural limitations of the vessel or severe fuel shortages constitute unavoidable field realities that practically and objectively limit the feasibility of immediate execution. Because the treaty mandate to take “all possible measures” inherently conditions the performance of the duty upon immediate physical capabilities, a failure or delay arising from such absolute operational deficits should not be construed as a breach of duty, provided that such relevant circumstances are properly proven. Crucially, while the aforementioned grounds provide persuasive legal baselines to preclude wrongfulness for a temporal delay, they do not grant commanders an elastic license or unlimited authority to bypass conventional duties indefinitely.

Above all, these operational realities do not relieve the Parties to a conflict of their continuing obligation to pursue rescue with diligence once circumstances permit. Commanders must remain prepared to initiate rescue efforts at any moment through continuous post-engagement situational assessment, and such a posture may be regarded as consistent with the ordinary meaning of Article 18 of the Convention. Where the Parties to the conflict cannot themselves conduct prompt rescue missions, they should make every feasible effort to mobilize all available nearby assets to facilitate rescue, including, where appropriate, those of the adversary. In practical terms, where neutral vessels are present near an engagement, they may serve as potential rescue assets, although the extent to which they may be compelled to assist is open to interpretation. In this context, the following section examines the interpretative limits imposed by the Convention on the role and use of neutral vessels in post-engagement rescue.

B. Interpretative challenges in applying “appeal to the charity” under Article 21

Article 21 of the Second Geneva Convention serves as a crucial legal instrument that extends the primary rescue obligations of the Parties to the conflict, as enshrined in Articles 12 and 18, to the broader maritime community. Its significance lies in institutionally enabling humanitarian rescue by neutral civilian vessels – not only where the Parties’ own capabilities are unavailable, but also where supplementary assistance is required. In doing so, the provision interfaces with the enduring rescue obligations of neutral mariners under peacetime maritime law, such as UNCLOS and SOLAS, which operate in parallel with IHL during an international armed conflict. By explicitly authorizing Parties to request that neutral commanders take on board the wounded, sick, or shipwrecked and collect the dead,Footnote ⁶² Article 21 operationalizes the mandate to take “all possible measures” for rescue, thereby ensuring that the combatants’ inherent duty is not constrained by their immediate military resources.

At the same time, the wording of the provision is notable because, in requesting rescue, it contains no terms carrying any legal compulsion, but rather encourages Parties to an armed conflict to “appeal to the charity” of commanders of neutral vessels. This choice of language seems to reflect a matter of humanitarian goodwill rather than legal obligation. In this respect, the reliance on the terms “appeal” and “charity”, when understood in good faith, sits uneasily with the exigent post-engagement distress scenarios where urgent assistance is required, thereby introducing some degree of ambiguity.Footnote ⁶³ As a result, the provision leaves room for interpretative debate as to whether such appeals may give rise to any binding legal effect, or whether they remain purely moral and humanitarian in character. This formulation, however, is not unique to the Second Geneva Convention. Similar language can be found in earlier instruments regulating humanitarian rescue in naval warfare, indicating a certain historical continuity in the legal treatment of assistance by neutral vessels.

Article 9 of the 1907 Hague Convention X likewise employs the expression “appeal to the charity” of the commanders of neutral vessels.Footnote ⁶⁴ This demonstrates that appeal to the charity was not an incidental choice of words, but a deliberately adopted formulation from the early stages of treaty law governing humanitarian rescue at sea. The continued use of this terminology may be understood as reflecting legislative prudence to respect the status of neutral States and to ensure that the navigational rights of neutral vessels are maintained notwithstanding hostilities between the Parties to the conflict. In other words, by refraining from imposing an explicit legal obligation, the drafters appear to have sought to prevent the erosion of neutral rights under the guise of humanitarian rescue. Nevertheless, the obligation to render assistance to persons in distress at sea is generally regarded as a customary duty,Footnote ⁶⁵ applicable in both peacetime and armed conflict, and binding on all vessels irrespective of nationality. From this perspective, the formulation “appeal to the charity” should be understood as a deliberately restrained expression; it simultaneously upholds the rights of neutral States and acts as an implicit call for the active participation of all vessels, acknowledging that the duty to rescue persists even in armed conflict.

The 2017 ICRC Commentary on the Second Geneva Convention notes that the wording “appeal to the charity” signifies that, from the perspective of IHL, commanders of neutral vessels are not subject to a strict legal obligation to comply with such requests, as the provision does not confer authority over them.Footnote ⁶⁶ Read literally, this might suggest that the decision to make such an appeal lies entirely within the discretion of the Parties to the conflict. However, this view should be evaluated alongside the fundamental legal duty of States to provide for the rescue of the shipwrecked under Articles 12 and 18 of the Convention. While the response of a neutral vessel remains voluntary, the State’s decision to initiate such an appeal is not a matter of unfettered discretion where external assistance is the only viable means to fulfil its inherent rescue obligations. In this sense, the “option” to appeal under Article 21 may effectively operate as an imperative for the Party to the conflict, ensuring that the State exhausts all possible measures in good faith to discharge its primary responsibility for rescue.

The conceptualization of Article 21 as an operational imperative rather than a matter of discretion is further illustrated when analysed against the backdrop of contemporary naval warfare and actual State practice. When a State exercises de facto tactical secrecy or immediate perimeter control over an engagement zoneFootnote ⁶⁷ but faces practical capacity constraints to execute immediate rescue itself, simply notifying distant coastal authorities may not fully exhaust the mission-related options envisaged under Articles 12 and 18. Instead, to give full practical effect to the core humanitarian objective of rescue, the legal regime encourages the active utilization of the institutional mechanism of Article 21 to coordinate with nearby commercial vessels bearing parallel peacetime rescue duties. The practical necessity of this approach is underscored by the aforementioned IRIS Dena incident, where the post-engagement coordination relied on remote regional authorities rather than an immediate appeal to nearby merchant shipping.Footnote ⁶⁸ This case highlights that in contemporary naval warfare, proactively mobilizing the available civilian maritime network through Article 21 remains a critical and necessary component for ensuring that the mandate to pursue rescue with all feasible means is fully incorporated into such maritime endeavours.

Overall, Article 21 encourages Parties to an armed conflict to seek the assistance of neutral vessels through an appeal to the charity, which frames such cooperation as motivated by humanitarian considerations rather than as a binding legal obligation. However, when considered alongside the customary law duty to rescue persons in distress at sea, applicable in both peacetime and armed conflict, as well as comparable obligations recognized in other international instruments, such an appeal cannot be regarded as merely discretionary. In particular, this interpretation must be read in light of the binding obligations of belligerent States under Article 18 to search for, collect, and care for the shipwrecked after armed engagement. From this systemic perspective, requests to neutral vessels must be interpreted in a manner consistent with the requirements of “all possible measures” and “without delay”, and, accordingly, neutral merchant vessels receiving such requests should, insofar as the circumstances permit, actively respond to them.

A. Balancing military necessity and humanity in the timing of post-engagement rescue

Defining the appropriate timing for post-engagement rescue activities remains a complex and contested issue. Given the objectives and nature of armed conflict, Parties are likely to devote their utmost efforts toward achieving military objectives, and in that process, humanitarian considerations can be easily overlooked. Although IHL has advanced considerably since the Second World War, it is unrealistic to expect combatants to observe humanitarian principles at every moment of combat. On the battlefield, the imperatives of military necessityFootnote ⁶⁹ can frequently override the principles and procedures established under IHL.Footnote ⁷⁰ For these military reasons, the humanitarian expectation that rescue must commence immediately upon the cessation of an engagement is inevitably qualified by operational realities. Consequently, the definition and practical implementation of the timing of rescue cannot be fully determined by abstract legal norms alone.

The 2017 ICRC Commentary on the Second Geneva Convention takes the position that the phrase “without delay” implies the feasibility of taking certain measures to search for and collect persons in distress at sea, even during ongoing engagements in the vicinity.Footnote ⁷¹ It further suggests that the mere fact that additional combat activities may occur later or nearby does not, in itself, render the implementation of some or all of the measures envisaged under Article 18(1) necessarily impossible.Footnote ⁷² While such an interpretative stance may be regarded as highly desirable from a humanitarian perspective, it also gives rise to certain concerns when viewed through the lens of military necessity. In naval warfare in particular, the beginning and end of an engagement are often difficult to ascertain with precision, and threats that appear to have subsided may re-emerge unexpectedly, posing potential risks to vessels and their crews. The Laconia incident during the Second World War provides a well-known illustration of these challenges. Admiral Dönitz was aware of the humanitarian imperative underlying the duty to rescue; yet he came to recognize that, in practice, rescue conducted immediately after an engagement could be tactically risky and might adversely affect subsequent engagements as well as overall military effectiveness.Footnote ⁷³ This episode underscores how, in naval warfare, the constant requirement for vigilance and readiness – namely, military necessity – may operate as a meaningful constraint on both the manner and timing of the implementation of rescue obligations.

In the specific context of post-engagement maritime rescue, military necessityFootnote ⁷⁴ manifests not in the permissibility of violence, but in the requirement to preserve tactical readiness and force protection during periods of heightened residual risk. Even where armed engagements are assessed as having subsided, the possibility of renewed hostile action – whether from surface, subsurface, or air – cannot be excluded, requiring commanders to maintain vigilance in their operational judgment. In its general application, military necessity is limited to the minimum degree and kind of force necessary to achieve a legitimate military objective, and not all claims of military necessity can justify acts that are barred under IHL.Footnote ⁷⁵ Crucially, while military necessity may condition the temporal feasibility of rescue, it cannot be invoked as an extrinsic legal justification to excuse a complete non-performance of the obligation itself.Footnote ⁷⁶ Moreover, the principle of humanity seeks to prevent unnecessary suffering, injury, or destruction and establishes fundamental standards for the protection of human dignity in armed conflict.Footnote ⁷⁷ The Martens Clause, which embodies that principle, declares that even in the absence of specific legal provisions, the conduct of hostilities must remain governed by established custom, the laws of humanity, and the dictates of public conscience.Footnote ⁷⁸

Importantly, IHL reflects a carefully negotiated balance between military necessity and humanity, such that the application of either principle alone cannot fully justify certain military conduct.Footnote ⁷⁹ This balance is inherent in the relative character of the two principles. When the anticipated military advantage of a given act is marginal, even limited incidental harm cannot be tolerated; by contrast, when the military advantage is substantial, a correspondingly greater degree of incidental harm may be considered justifiable.Footnote ⁸⁰ Accordingly, whether by action or omission, a belligerent Party should bear legal responsibility for incidental harm that is excessive in relation to the concrete and direct military advantage anticipated. It should not be overlooked that an omission consisting in a State’s failure to carry out conduct required of it may also constitute an internationally wrongful act.Footnote ⁸¹ This interpretation is of particular significance in determining the timing of rescue following naval engagements. In such situations, military necessity may justify a delay in rescue measures, while the principle of humanity requires that rescue be carried out as promptly as possible, thereby giving rise to a concrete tension between the two principles within the framework of IHL.

In an environment still marked by the immediate aftermath of an engagement, a central question arises as to how a commander of a belligerent Party can realistically initiate rescue activities “without delay”. On the one hand, humanitarian expectations dictate that immediate rescue measures be undertaken even where hostilities continue in the vicinity; on the other hand, operational judgment demands the deferral of such measures until surrounding threats have been sufficiently neutralized and a safer opportunity presents itself. Accordingly, once a reasonable period has passed following the termination of an engagement and no additional threats are present, the commander is required to commence rescue efforts pursuant to humanitarian imperatives, that is, within the bounds of lawful action. It should be noted that the prolonged abandonment of persons in distress – particularly in cold waters or open maritime environments – may be regarded as a failure to fulfil the obligation to rescue,Footnote ⁸² constituting an omission. In view of this risk, commanders should, where necessary, be able to demonstrate that rescue activities were initiated with feasible immediacy following the cessation of an engagement.

However, such immediacy should not be understood as an absolute temporal requirement. Rather, the timing of rescue needs to be assessed in light of the circumstances, using the concept of a “reasonable time”.Footnote ⁸³ In international law, the fulfilment of many obligations has been assessed by reference to whether they were carried out within a reasonable period, from which the lesson has been drawn that a failure to take appropriate action once that period has elapsed may constitute an internationally wrongful act.Footnote ⁸⁴ The severity of the consequences resulting from such omissions may influence the assessment of whether they amount to a war crimeFootnote ⁸⁵ or instead constitute an internationally wrongful act falling below that threshold. In particular, unreasonably leaving shipwrecked persons without assistance beyond a reasonable period following the cessation of an engagement cannot be excluded as potentially amounting to a war crime. Accordingly, the factors invoked to justify any delay in rescue must be capable of contributing to a context-sensitive assessment that accounts for the timing of such delayed rescue efforts. By taking these factors into account, commanders should be prepared to articulate a rationale demonstrating that rescue activities were initiated as promptly as circumstances reasonably permitted.

Although the determination of a reasonable time is inherently context-specific, international jurisprudence and doctrine have identified recurring analytical considerations for assessing reasonableness, which – by analogy – are equally relevant to the timing of post-engagement rescue situations. Such considerations typically encompass, inter alia, factors relating to residual enemy risks, operational capacity, temporal proximity following awareness, prevailing environmental conditions, vulnerability of the shipwrecked, the scope of the actor’s knowledge, and the internal coherence of the reasons advanced. Among these, this latter consideration contributes logically to the justification of delayed or omitted rescue by linking the other factors within a consistent explanatory framework. This dynamic is illustrated by the ICJ in the Corfu Channel case, where Albania advanced alternative arguments concerning its knowledge of the minefield in the territorial sea, but the Court found that these explanations were irreconcilable with the overall factual record and Albania’s conduct, ultimately holding the State responsible for failing to warn of the known danger.Footnote ⁸⁶ The judgment thus demonstrates how internal inconsistency in the reasons advanced may undermine their persuasive and legal weight.

However, different considerations may apply to submarines. Since the Second World War, submarines have evolved predominantly as submerged platforms and, as a consequence of this design orientation, exhibit markedly reduced manoeuvrability and survivability when operating on the surface.Footnote ⁸⁷ Given these inherent limitations, surfacing after an engagement, approaching persons in distress, and conducting rescue missions entail significant time, tactical risk, and structural limitations when compared to surface vessels.Footnote ⁸⁸ During the First World War, when submarines still operated partly on the surface, German U-boats incurred significant losses during stop-and-search engagements against merchant vessels, largely due to their exposure to disguised Q-shipsFootnote ⁸⁹; in the Second World War, the issuance of the Laconia Order following the Laconia incident further demonstrated that surfacing rendered submarines directly vulnerable to enemy attack. This operational constraint was reaffirmed in 1982 when HMS Conqueror withdrew at high speed after the Belgrano engagement to evade potential counter-strikes rather than surfacing for rescue.

Nevertheless, the IRIS Dena incident presents a highly controversial case, as the US submarine failed to fully discharge its primary duty as a combatant to render assistance without delay in the absence of additional hostile threats at the scene. While the US asset did notify remote coastal authorities, it did so without proactively initiating an appeal to nearby merchant shipping – an institutional mechanism under Article 21 that could have mobilized immediate civilian maritime networks. Furthermore, under the framework of the law on State responsibility, leaving the scene without exhausting such feasible options or initiating direct rescue in an environment devoid of a “grave and imminent peril” to the essential interests of the State appears clearly insufficient to satisfy the threshold for precluding wrongfulness. Against this evaluative background, while the particular constraints facing submarines may allow for a more flexible application of immediacy depending on the contextual threat level, they do not offer an absolute exemption from direct rescue efforts. Rather, a submarine’s choice to discharge its obligations through third-party notification must be strictly appraised against the actual presence of an imminent peril. Where secure conditions permit, a departure from the scene – without exhausting all feasible rescue options, including direct rescue efforts – may arguably constitute an unwarranted omission that fails to satisfy the threshold for legal justification under international law.

In sum, determining the timing of post-engagement rescue requires a contextual balancing of military necessity and humanitarian considerations. While the 2017 ICRC Commentary on the Second Geneva Convention suggests that rescue measures may be feasible even amid nearby engagements,Footnote ⁹⁰ historical naval practice demonstrates that premature rescue efforts can expose forces to grave danger. Crucially, once a reasonable interval – assessed in light of the relevant operational factors – has passed and no imminent threats remain, commanders must act without delay. For submarines, while their inherent design constraints and operational vulnerability necessitate a flexible application of immediacy, they do not grant an exemption from the fundamental duty to assist. Therefore, even for these platforms, commanders remain obligated to exhaust all feasible rescue options, including direct action, once the security environment permits.

B. Practical measures for post-engagement rescue

Rescue activities conducted immediately after an engagement may entail relatively limited procedural complexity when carried out by a single vessel; however, they can become significantly more complex when multiple vessels participate simultaneously or sequentially, with irregular time lags and sustained involvement. This complexity is further compounded where residual enemy threats persist, as such conditions expose rescue vessels to heightened risk and may hinder prompt and well-coordinated rescue efforts. Accordingly, in order to ensure the safety of assets participating in the rescue and to encourage their involvement, it is necessary to identify a decisive temporal point marking the commencement of post-engagement rescue. On this basis, the initiation of humanitarian rescue obligations may be formally declared.

Such declaratory actions, effected by a Party to the conflict, can generate several positive impacts. First, they can serve as a warning to adversary forces not to regard the assets participating in the rescue as hostile combat reinforcements. If properly communicated to the adversary, this warning may prevent unnecessary additional engagements and eliminate the risk of misidentification, thereby enabling safer and more effective rescue activities. Second, by signalling the commencement of humanitarian rescue to friendly forces, the declaration may convey an expectation of additional reinforcements or support. During the Second World War, for instance, in the Laconia incident, the U-boat command stationed in France promptly dispatched additional assets for rescue efforts at the request of the on-scene commander, thereby facilitating a multi-asset endeavour.Footnote ⁹¹ Third, such a declaration may draw the attention of nearby neutral vessels and encourage the active participation of available ships. On 29 December 1943, the Irish small merchant vessel Kerlogue, belonging to a neutral State, received a distress signal from a German bomber circling overhead while sailing from Lisbon to Dublin, proceeded to the Bay of Biscay, and successfully rescued numerous survivors clinging to wreckage following an engagement between Allied and German forces.Footnote ⁹²

In this context, determining the appropriate moment to commence a safe rescue presents a particularly challenging task. Commanders, although inherently focused on the achievement of military objectives, must continuously assess both the humanitarian imperative and tactical risks in order to determine the point at which the former should be accorded priority. Subject to the circumstances prevailing after an engagement, the commander is under an obligation to participate in rescue as soon as feasible, even where a certain passage of time is unavoidable. For these reasons, this paper introduces the term Humanitarian Rescue Moment (HRM) to denote the temporal point at which post-engagement rescue obligations become formally actionable. The HRM serves three complementary purposes: as a procedural trigger to operationalize the initiation of rescue, as an evidentiary safeguard documenting compliance with IHL, and as a confidence-building mechanism indicating the commencement of humanitarian activities to both adversary and neutral forces, thereby enhancing the safety and coordination of participating assets. To fulfil these functions, the HRM may be implemented and communicated by reference to the distress signals under the International Regulations for Preventing Collisions at Sea.Footnote ⁹³

To ensure that the HRM remains a strictly non-combat undertaking, it is essential to address the potential for its operational abuse. The authority to initiate and declare the operationalization of the HRM should reside with the commanders of the Parties to the conflict on the scene, who are best positioned to assess the tactical situation and humanitarian needs. Since a warship engaged in rescue inherently retains its legal status as a legitimate military objective under IHL, its prolonged presence in a combat zone may readily be perceived as a tactical threat rather than a humanitarian undertaking.Footnote ⁹⁴ To mitigate such risks, the HRM should incorporate temporal and spatial limitations that delineate the boundaries of protected rescue activities. To this end, the “24-hour rule” established under Article 12 of the 1907 Hague Convention XIIIFootnote ⁹⁵ provides a vital normative reference. Just as this rule prevents neutral ports from being used as safe havens or tactical bases, applying a similar objective timeframe to the HRM ensures that rescue efforts do not devolve into a ruse for gathering intelligence or reconstituting combat power. By adopting such clear temporal constraints, the HRM can prevent the indefinite presence of warships under the guise of rescue, thereby safeguarding the integrity of the mission and reducing the likelihood of escalatory counter-strikes.Footnote ⁹⁶

As applied to submarines, significant practical limitations arise in surfacing to conduct direct rescues, due to constraints in underwater communication, heightened vulnerability when surfaced, and difficulties in accommodating multiple survivors on board. While surfacing for rescue is generally expected, such measures may be militarily impossible or entail excessive risk. In these cases, alternative methods can be justified, primarily through the immediate dissemination of distress information and feasible communication of the need for rescue.Footnote ⁹⁷ However, the requirement that submarines operate near the sea surface in order to employ communication equipment entails a continued reduction in survivability and inherent temporal delays, which must be taken into account.Footnote ⁹⁸ Even under these constraints, a submarine can operationalize the HRM as a procedural and evidentiary tool, thereby triggering and encouraging participation of friendly or third-party assets. Notwithstanding the practical impossibility or delay of direct rescue, this approach may serve to demonstrate the submarine’s faithful fulfilment of its humanitarian obligations.

Another measure to encourage expeditious and safe participation in rescue following an engagement is the use of distinctively visible means of identification on vessels indicating that they are engaged in humanitarian rescue activities. While the Second Geneva Convention and Additional Protocol IFootnote ⁹⁹ explicitly regulate external markings for dedicated medical and rescue assets, such as hospital ships or coastal rescue craft,Footnote ¹⁰⁰ they contain no provisions regarding the visible identification of vessels or other assets participating in rescue missions after an engagement. This regulatory gap means that assets involved in post-engagement rescue may lack clear means of identification, making it difficult to ensure their safety during their missions and to effectively benefit from the protection or privileges under IHL. Accordingly, it is necessary to establish externally recognizable means of identification for such assets, from the moment rescue efforts commence. Possible measures include visual means, such as signal flags or temporarily installed fixtures, that can be rapidly implemented or displayed in the aftermath of engagements; in particular, the provisional installation of large, deck-mounted flag-type displays clearly visible from the air would facilitate identification by aircraft and significantly enhance the safety of rescue activities. Of course, the use of such displays carries the risk of misuse or deliberate abuse, for example by disguising a vessel for the purpose of carrying out a surprise attack. Nevertheless, enabling rescue-participating assets to operate safely through such identification is a measure that should be actively encouraged and pursued from a humanitarian perspective. Furthermore, any deliberate abuse of such displays should be regarded as perfidy and may constitute a war crime, requiring appropriate international accountability measures.Footnote ¹⁰¹

In rescue efforts, the simultaneous participation of multiple military and civilian assets may give rise to problems such as communication congestion, tactical inefficiency, and greater operational risks to rescue assets. While internationally recognized distress, urgency, and safety communication procedures exist in peacetime,Footnote ¹⁰² no dedicated humanitarian communication network exists for post-engagement rescue. As a result, practical difficulties accumulate in the rescue phase, including the allocation of search areas, coordination of manoeuvring among rescue assets, and mutual identification between aircraft and vessels. IHL requires Parties to the conflict to take “all possible measures” to rescue persons in distress; however, uncoordinated multilateral involvement may paradoxically expose both rescue assets and survivors to additional and unreasonable risks. In other words, a greater number of participating assets does not automatically enhance the safety or effectiveness of rescue efforts; rather, there arises a paradox whereby the deployment of a smaller number of well-coordinated assets may produce a more genuinely humanitarian outcome. In light of these concerns, there is a growing need to establish, at the international level, dedicated communication networks, communication procedures, and minimum common operational frameworks specifically tailored to post-engagement rescue situations. Such efforts and their resulting outcomes may contribute to the international community’s recognition of rescue obligations arising after the cessation of an engagement as a clearly defined legal norm under IHL.

As noted earlier, Article 21 of the Convention provides a legal basis for a Party to the conflict to request assistance from the master of a neutral vessel, without establishing an explicit international legal obligation on the part of that master to comply. Nonetheless, it should be understood as a practical means for a Party to fulfil its rescue obligations under Articles 12 and 18 of the Convention, and as a request that should be regarded as carrying the weight of a humanitarian and legal duty. Accordingly, a neutral vessel receiving such a request should not treat it merely as a matter of voluntary discretion, but rather is expected, in the absence of exceptional circumstances, to respond actively in a manner consistent with the spirit of IHL. With respect to the protection afforded to such neutral vessels, Article 21(2) provides that a responding neutral vessel may enjoy “facilities for special protection and support”, and Article 21(3) specifies that it is generally exempt from capture, thereby safeguarding the legal status of neutral vessels participating in humanitarian rescue.

Importantly, no specific provision currently defines the scope of “exceptional circumstances” that may prevent a neutral vessel from responding, and its interpretation remains ambiguous. While a more detailed discussion is necessary, clearly identifiable exceptions – such as engine failure or an inability to navigate due to force majeure – should be explicitly enumerated, thereby delineating the situations in which a neutral vessel’s unavoidable non-response can be objectively justified. Regarding the interpretation and application of these provisions, greater clarity and practical support may be facilitated through the technical expertise of international organizations, including the ICRC, in a manner that assists States in fulfilling their treaty obligations. Ultimately, the advancement of IHL regarding post-engagement rescue may depend less on the addition of new individual rules than on the enhancement of procedural and institutional mechanisms that effectively implement and concretize existing norms. In this regard, the San Remo Manual, for which a revision is being pursued,Footnote ¹⁰³ should carefully identify the contemporary challenges associated with rescue obligations following engagements and, in particular, provide guidance on practical mission-related issues, including rescue coordination centres, radio communication networks and procedures, and other fundamental operational protocols.Footnote ¹⁰⁴

In sum, post-engagement maritime rescue is complicated by various factors that make commanders’ judgment and prompt action more difficult. Accordingly, to effectively fulfil humanitarian rescue obligations, it is necessary to appropriately and decisively determine the HRM through the on-scene commander’s authority and to indicate it through signalling systems and external markings, thereby ensuring the safety and cooperation of participating assets. Furthermore, the implementation of the HRM should be governed by temporal and spatial constraints, such as the spirit of the 24-hour rule, to prevent tactical abuse and maintain humanitarian integrity. Assets with significant physical constraints, such as submarines, should, of course, conduct direct rescue activities if circumstances allow; however, they may more effectively fulfil their obligations through prompt reporting of the situation and coordination with nearby assets. When multiple assets are involved in rescue, communication congestion and tactical inefficiency may arise, making it necessary at the international level to establish dedicated communication networks and minimum common procedural frameworks. Ultimately, post-engagement rescue cannot be adequately addressed by mere compliance with legal norms; it requires the establishment of institutional mechanisms that account for operational realities and humanitarian principles, alongside proactive interpretative efforts led by international organizations.