Introduction
Europe has increasingly been portrayed as strategically weak, militarily dependent on the United States, politically fragmented, and unable to deter aggression on its own continent.Footnote 1 President Trump’s repeated accusations that Europe cannot defend itself, coupled with demands for sharply increased NΑTO defence spending, have brought this critique into sharp relief.Footnote 2 Yet such claims often overlook a crucial historical and legal dimension. Europe’s post-war security posture was neither an accident nor solely the product of political choice. It was shaped by a dense web of treaties, alliances, and normative commitments designed to prevent the recurrence of catastrophic wars on the European continent.
The end of the Cold War generated profound optimism regarding the future of European security. The collapse of bipolar confrontation, the expansion of economic interdependence, and the institutionalisation of arms control regimes encouraged the widespread perception that Europe had entered a fundamentally transformed strategic environment in which large-scale interstate war had become increasingly unlikely. Across much of Europe, defence spending declined substantially, military force structures were reduced, and strategic attention shifted from territorial defence towards crisis management, peacekeeping, and institutional cooperation. Simultaneously, arms control treaties, multilateral organisations, and legal frameworks became increasingly central components of European security governance.
Yet the re-emergence of geopolitical confrontation in Europe, particularly following the deterioration of relations between Russia and the West, exposed significant structural vulnerabilities within European defence capabilities and strategic preparedness. Europe’s contemporary security predicament therefore raises a broader analytical question: how did a continent historically shaped by military competition and strategic balancing become so deeply reliant upon external guarantees and so institutionally committed to military restraint?
Theoretical and conceptual framework
Existing explanations of post–Cold War European security predominantly emphasise US primacy, alliance dependence, and NΑTO-centred security hierarchy as the principal foundations of European strategic retrenchment. Within these approaches, military restraint among European states is generally interpreted as a rational response to the stabilising effects of American security guarantees and the diminished likelihood of interstate conflict following the collapse of the Soviet Union. Recent scholarship has also highlighted the persistence of European military dependence upon the United States and the structural limitations of European strategic autonomy. Stephen G. Brooks and Benjamin Meijer, for example, argue that Europe lacks the military capabilities required for independent territorial defence and remains deeply reliant upon American power projection, intelligence, logistics, and strategic infrastructure. Such accounts convincingly explain important material dimensions of European strategic dependence.Footnote 3
At the same time, scholarship on the post–Cold War order has often focused on NΑTO enlargement and the consolidation of Western institutional predominance. Scholars such as Mary Elise Sarotte and Timothy Hill emphasise how post–Cold War institutional arrangements increasingly privileged NΑTO-centred security structures while limiting Russia’s role within the evolving European order.Footnote 4 Yet this interpretation does not fully capture the broader multilateral orientation that also characterised the 1990s and early 2000s. The institutionalisation of the Organization for Security and Co-operation in Europe in 1995, Russia’s admission to the Council of Europe in 1996, and its later accession to the World Trade Organization reflected parallel Western efforts to integrate Russia into cooperative legal, political, and economic frameworks rather than simply exclude it from the post–Cold War European order.Footnote 5 Even discussions concerning possible forms of cooperation or future association between Russia and NΑTO, however limited and ultimately unsuccessful, illustrated the broader assumption that post–Cold War European security could increasingly be organised through institutional engagement and cooperative integration rather than traditional geopolitical confrontation.Footnote 6 A NΑTO–Russia Council functioned well until 2014, when Russia annexed Crimea; limited meetings continued to occur until Russian aggression against eastern Ukraine, at which point NΑTO declared that it could no longer consider Russia a partner, effectively bringing an end to the functioning of the partnership to that point.Footnote 7
This article does not reject these explanations. Rather, it advances a different, though complementary, argument. It argues that Europe’s post–Cold War strategic retrenchment cannot be understood solely through alliance politics, hegemonic hierarchy, or American security guarantees. Instead, the article shifts analytical attention towards the constitutive role of legal and arms control regimes in reshaping European strategic culture after the Cold War.
A significant body of literature has conceptualised the European Union as a ‘civilian power’Footnote 8 or, later, as a ‘normative power’,Footnote 9 emphasising its reliance on law, economic integration, and multilateral institutions rather than military force. This scholarship views Europe’s restraint as not weakness but rather transformation, a deliberate departure from traditional power politics. Critics, however, have argued that this self-image obscures continued reliance on US hard power and NΑTO’s security umbrella.Footnote 10 Another strand of literature focuses on NΑTO burden-sharing, recurrently criticising European underinvestment in defence.Footnote 11 Scholars such as Walt, Mearsheimer, and Posen have framed Europe’s dependence as a rational response to US dominance, while policy-oriented analyses emphasise free-riding dynamics.Footnote 12 Yet this literature often under-theorises the legal and treaty-based constraints that structured European demilitarisation. Legal scholars have examined arms control treaties primarily through lenses of verification, compliance, and stability. The Helsinki Final Act, CFE, INF, and NPT are frequently treated as technical instruments rather than constitutional elements of a broader security order. This article departs from that approach by treating arms control regimes as constitutive constraints that reshaped European strategic culture.Footnote 13 Recent literature on the erosion of the liberal international order by Ikenberry, Krasner, and others provides the broader theoretical context for this analysis.Footnote 14 Russia’s revisionism and US ambivalence under the Trump administration are seen as twin pressures destabilising an order once thought durable. This article contributes by highlighting how Europe has been uniquely exposed by its deep legal internalisation of that order.
This article conceptualises treaty-based security regimes as not merely regulatory instruments or derivative expressions of geopolitical order but also constitutive institutional structures capable of reshaping strategic expectations, defence planning, procurement priorities, and broader strategic culture over time. While existing literature frequently treats arms control arrangements as secondary manifestations of underlying power relations, the argument advanced here is that such legal–security regimes exerted independent and long-term effects upon European understandings of security, interstate conflict, and military necessity.
Importantly, the article’s analytical focus is neither NΑTO enlargement as such nor NΑTO’s original Cold War role as a Euro–Atlantic collective defence alliance established to contain Soviet influence in Western Europe. Rather, the article focuses on the broader treaty-based security architecture that emerged during and after the Cold War and that included Russia itself as a central participant. Agreements such as the NPT, INF Treaty, the CFE Treaty, and broader arms control frameworks were negotiated primarily between the United States and the Soviet Union/Russia and reflected wider efforts to institutionalise strategic restraint through reciprocal legal commitments. Although distinct from NΑTO’s alliance structure, these arrangements nevertheless exerted significant influence on European security policies, including the substantial reduction of defence spending and force structures among many European NΑTO member states during the 1990s and early 2000s.
The article further argues that these legal–security arrangements operated within a broader normative environment characterised by strong confidence in cooperative security, multilateral governance, and the capacity of international law to regulate interstate relations. The institutionalisation of the Organization for Security and Co-operation in Europe in 1995 reflected broader assumptions that inclusive and rule-based security arrangements could progressively replace traditional geopolitical balancing within Europe. During the 1990s and early 2000s, arms control, institutional cooperation, and economic interdependence increasingly came to be viewed as not merely complementary mechanisms of stability but also viable substitutes for classical power politics.
In this respect, the article also engages with broader debates concerning the nature and viability of the post–Cold War liberal order. Critics such as Patrick Porter have questioned the coherence and sustainability of liberal international order narratives and warned against assumptions that institutional frameworks could durably transcend geopolitical competition.Footnote 15 The present article does not depend upon the assumption that a fully coherent liberal order objectively existed. Rather, its argument is that many European states increasingly acted upon the belief that cooperative security, legal institutionalisation, and economic interdependence had substantially reduced the likelihood of large-scale interstate conflict within Europe. These assumptions profoundly shaped defence planning, procurement patterns, and strategic priorities across much of the continent.
The post–Cold War embrace of strategic restraint was particularly visible in Germany, where the notion of ‘civilian power’, most prominently associated with Hanns W. Maull, became closely linked to preferences for multilateral diplomacy, economic influence, and military caution. Originally developed in the German and Japanese contexts, the civilian power concept reflected the broader post–Cold War belief that economic interdependence, institutional integration, and normative legitimacy could increasingly displace traditional forms of geopolitical competition.Footnote 16 In this sense, Germany represented perhaps the clearest expression of wider European assumptions that institutionalised cooperation and legal frameworks had reduced the centrality of military power within Europe.
This broader normative transformation was also reflected materially in European defence policies. Following the end of the Cold War, many NΑTO member states significantly reduced defence spending and force structures, reflecting the widespread belief that territorial military confrontation in Europe had become unlikely. NΑTO itself increasingly shifted its strategic focus during the 1990s from territorial defence towards crisis management, stabilisation operations, and partnership frameworks. Importantly, however, these transformations were not experienced uniformly across the continent. While many Western European states increasingly embraced post-geopolitical assumptions grounded in multilateralism and economic integration, several Eastern European states continued to perceive traditional security vulnerabilities and therefore strongly supported NΑTO enlargement as a means of obtaining strategic reassurance against potential future instability. The coexistence of NΑTO enlargement and broader European military retrenchment therefore reflected differing historical experiences and threat perceptions within Europe rather than a singular strategic logic.
This article therefore treats legal–security regimes as not merely dependent variables of geopolitical order but also institutional arrangements capable of producing path-dependent strategic consequences. Over time, sustained reductions in defence spending, procurement capacity, force structures, and military–industrial capability became embedded within broader European security policy and increasingly difficult to reverse rapidly once geopolitical competition re-emerged. Europe’s contemporary strategic vulnerabilities therefore must be understood through not only material dependence on the United States but also the long-term institutionalisation of treaty-based restraint within the post–Cold War European security order.
Contribution, methodology, and structure
This article contributes to debates on post–Cold War European security in three principal ways. First, it shifts analytical attention from NΑTO enlargement and alliance politics alone towards the constitutive role of legal and arms control regimes in shaping European strategic culture after the Cold War. Second, it demonstrates how treaty-based security arrangements contributed to the normative internalisation of strategic restraint and reinforced the belief that interstate war in Europe had become increasingly improbable. Third, it highlights the path-dependent consequences of this post–Cold War security paradigm by demonstrating how decades of military retrenchment and reliance on cooperative security frameworks generated structural vulnerabilities that became increasingly visible following the erosion of reciprocity within the European security order.
Methodologically, the article adopts a qualitative and historically contextual analysis of post–Cold War treaty frameworks, arms control arrangements, strategic doctrines, and European defence policies. It examines how legal–security regimes shaped broader strategic expectations and contributed to long-term transformations in European military planning and security governance.
The article proceeds in three parts. The first substantive section examines the evolution of post–Cold War treaty-based security arrangements and their relationship to broader European security governance. The following section analyses the long-term strategic consequences of European military retrenchment and the erosion of cooperative security assumptions following the return of geopolitical confrontation in Europe. The conclusion reflects upon the contemporary implications of these transformations for the future of European security and transatlantic relations.
This article uses the term ‘Europe’ in a differentiated sense. On the one hand, Europe denotes the continental security space shaped by shared geography, historical experience, and interdependent threat perceptions. On the other hand, Europe refers more specifically to the European Union as a highly integrated political and legal entity endowed with supranational characteristics. While these meanings overlap, they are not synonymous, and failure to distinguish between them has contributed to analytical ambiguity in debates about European weakness and responsibility. Within this landscape, NΑTO continues to function as the primary framework for collective defence, particularly with regard to high-intensity military threats. Yet outside NΑTO’s operational structures, the European Union, together with key European states including the United Kingdom, remains central to the protection and promotion of a community of liberal democratic values. These values, enshrined in EU treaties and political practice, constitute not merely internal standards but also external reference points for European security and stability. Both organisations are anchored in democracy, the rule of law, human rights, and collective defence, and this normative overlap is repeatedly emphasised in treaty law and political declarations. The Treaty of Lisbon formally embeds NΑTO into the EU’s security architecture by recognising it as the foundation of collective defence for its members, while successive EU–NΑTO Joint Declarations (2016, 2018, 2023) operationalise this relationship through concrete cooperation in areas such as hybrid threats, cyber defence, military mobility, and crisis management.Footnote 17 Prospective member states across the European continent, including Ukraine, Moldova, and the Western Balkan states, are part of this broader European security and normative space. Their aspirations to join the European Union are inseparable from commitments to democracy, the rule of law, and respect for territorial integrity. Consequently, threats to these states are not peripheral but rather integral to Europe’s security environment. Russia’s aggression against Ukraine therefore represents not only a violation of international law but also a direct challenge to the normative foundations of Europe as a political project.
The treaty architecture of European restraint
Europe’s contemporary strategic posture cannot be understood without reference to the legal architecture that disciplined, limited, and redirected its military power towards the end of and after the Cold War.Footnote 18 The Helsinki Final Act, the CFE Treaty, the INF Treaty, and the NPT functioned as not merely arms control instruments but also constitutive elements of a broader security settlement. Collectively, they normalised restraint, entrenched asymmetry, and fostered a European strategic culture premised on law, predictability, and externalised deterrence.
The Cold War was defined by a persistent and pervasive sense of existential insecurity. From its earliest stages, the confrontation between the United States and the Soviet Union was characterised by not direct armed conflict between the two superpowers but rather an unprecedented accumulation of military capabilities, particularly in the nuclear domain. Security was conceptualised in zero-sum terms, and stability was sought through deterrence rather than cooperation. This logic produced a sustained arms race that shaped international relations for nearly half a century.Footnote 19 Both blocs invested heavily in conventional and nuclear forces, driven by the assumption that military superiority, or at least parity, was essential to survival. Europe occupied a central position in this strategic competition. Divided by ideological, political, and military fault lines, the continent became the primary theatre for potential confrontation. The stationing of massive conventional forces and nuclear weapons on European soil rendered the region uniquely vulnerable, transforming it into both a shield and a potential battlefield in the event of escalation.Footnote 20 The risk inherent in this military build-up became increasingly apparent as the Cold War progressed. The Cuban Missile Crisis of 1962 marked the most acute moment of danger, bringing the world to the brink of nuclear war. For thirteen days, miscalculation, miscommunication, or political misjudgement could have triggered a catastrophic conflict with global consequences. The crisis exposed the fragility of deterrence and underscored how close the international system had come to a third world war.Footnote 21
This near-catastrophe profoundly affected strategic thinking on both sides. While deterrence remained central, it was increasingly accompanied by a recognition that unregulated military competition carried unacceptable risks. Communication channels, crisis management mechanisms, and confidence-building measures began to emerge as necessary complements to deterrence. The objective was not trust but rather predictability, an acknowledgement that mutual vulnerability required some degree of restraint.Footnote 22 Throughout the 1960s and 1970s, this realisation gradually translated into more structured forms of dialogue and cooperation. Arms control initiatives such as the Strategic Arms Limitation Talks (SALT) and later the Anti-Ballistic Missile (ABM) Treaty reflected an emerging consensus that stability could be enhanced by legally binding limitations on military capabilities. These efforts sought to reduce incentives for pre-emptive strikes and to manage competition rather than eliminate it.Footnote 23
Parallel to bilateral superpower negotiations, a broader European process of security dialogue took shape through the Conference on Security and Cooperation in Europe (CSCE). Launched in the early 1970s and culminating in the Helsinki Final Act of 1975, the CSCE represented a novel attempt to institutionalise security through inclusivity, norms, and dialogue rather than alliance-based deterrence alone. Unlike traditional treaties, the Helsinki Final Act was not legally binding in the strict sense. Its significance lay instead in the political commitments it articulated and the normative framework it established.Footnote 24 The Helsinki Final Act codified a set of foundational principles that would come to define the European security order. These included the sovereign equality of states, the inviolability of frontiers, territorial integrity, non-use of force, non-intervention in internal affairs, and respect for human rights and fundamental freedoms. Importantly, it also affirmed the right of peoples to self-determination, linking security with political legitimacy and internal governance.Footnote 25 By embedding these principles in a multilateral framework that included both NΑTO and Warsaw Pact states, the CSCE contributed to a gradual transformation of European security thinking. It indicated a shift away from the exclusive reliance on military power towards a conception of security rooted in law, norms, and cooperation. While military confrontation did not disappear, it became increasingly constrained by shared expectations and regularised dialogue.
The end of the Cold War did not mark the abandonment of this approach. Rather, it reinforced the belief that military restraint and legal commitments had contributed to a peaceful outcome. The collapse of the Soviet bloc appeared to validate the assumption that arms control, confidence-building measures, and normative engagement could substitute for force as organising principles of European security. This belief would later underpin the extensive network of arms control treaties and legal constraints that shaped Europe’s post–Cold War strategic posture.Footnote 26 The legacy of the Cold War thus lies in not only the dangers it posed but also the institutional responses it generated. The experience of near-catastrophic escalation, combined with the gradual normalisation of dialogue and restraint, created the conditions for a security order in which law was expected to discipline power. Understanding this historical trajectory is essential to explaining why Europe so fully embraced treaty-based limitations, and why the erosion of those commitments today has such profound consequences.Footnote 27
The Conventional Armed Forces in Europe (CFE) Treaty
The CFE Treaty,Footnote 28 signed in Paris on 19 November 1990 and entering into force in 1992, established comprehensive numerical limits on key categories of conventional military equipment, battle tanks, armoured combat vehicles, artillery, combat aircraft, and attack helicopters across the European continent. Its declared objective was to eliminate the capacity for surprise attack and large-scale offensive operations in Europe.Footnote 29 From a legal perspective, the CFE Treaty represented an unprecedented intrusion into state sovereignty in the realm of force posture. It imposed binding ceilings, geographic sub-limits, and verification mechanisms that went well beyond traditional confidence-building measures.Footnote 30 For European NΑTO members, compliance required substantial force reductions and structural reorganisation of armed forces. These measures were politically acceptable because they were embedded in a wider promise: that Europe had exited the age of territorial conquest and entered an era of cooperative security.Footnote 31 Europe appeared to leave behind its recent past and reconstructed its threat perception.Footnote 32
Importantly, the treaty’s design reflected the strategic priorities of the two principal military powers of the time, the United States and the Soviet Union.Footnote 33 While Western European states were formal parties, their room for manoeuvre was limited. The treaty locked in asymmetries that later became more pronounced as Russia adapted its doctrine while Europe internalised restraint as a normative good.Footnote 34 However, the CFE Treaty appeared to represent the most ambitious attempt to eliminate the possibility of large-scale conventional war on the European continent by reducing the means available to wage a large war.Footnote 35
Yet the geographic logic of the CFE Treaty embedded a structural imbalance from the outset. While the treaty formally applied to both NΑTO and Warsaw Pact states, its practical effect was to constrain military deployments primarily within the European territory of participating states. For European countries, particularly those that are geographically compact and densely populated, CFE ceilings translated into binding and enduring limitations on force posture, procurement, and military planning. Compliance required not only numerical reductions but also long-term doctrinal adaptation towards lower-intensity, defensive force structures.Footnote 36 By contrast, both the United StatesFootnote 37 and the Russian FederationFootnote 38 retained strategic depth beyond the treaty’s effective reach. The United States, whose continental territory lay largely outside the CFE area of application, could maintain and modernise substantial conventional capabilities without those forces being subject to treaty ceilings, while still projecting power into Europe through rotational deployments. Russia, inheriting the vast territorial expanse of the Soviet Union, enjoyed even greater flexibility. Large portions of its military infrastructure and reserve forces lay east of the Urals, beyond the CFE zone, enabling Moscow to relocate, reconstitute, or reinforce units without formally breaching treaty limits.Footnote 39 This asymmetry became more pronounced after the dissolution of the Warsaw Pact and NΑTO’s subsequent enlargement. While new NΑTO members in Central and Eastern Europe accepted CFE constraints as part of their integration into the Euro–Atlantic security order, Russia increasingly perceived the treaty as a one-sided restriction. In practice, however, the imbalance favoured Moscow’s ability to exploit geographic scale rather than constraining it. Russia could maintain compliance on paper while retaining the capacity to rapidly reintroduce forces into the treaty area, particularly along its western military districts, thereby preserving escalation dominance over neighbouring states.Footnote 40
The result was a paradoxical outcome: a treaty designed to equalise security and reduce the risk of conventional war contributed, over time, to the relative demilitarisation of much of Europe while leaving the major military powers less constrained in strategic terms. This dynamic reinforced European dependence on US enablers and, in Russia’s case, enabled the selective manipulation and eventual suspension of treaty obligations. The erosion and ultimate collapse of the CFE regime thus did not merely signal the failure of arms control compliance. It also exposed the limits of geographically bounded restraint in a security environment marked by asymmetric territory, power projection, and divergent strategic cultures.Footnote 41 Russia’s suspension of the CFE Treaty in 2007, citing NΑTO enlargement and alleged imbalance, marked a turning point.Footnote 42 While Russia gradually disengaged from its obligations, most European states remained normatively committed to the treaty’s logic. This asymmetrical compliance contributed to a widening gap between legal restraint and strategic reality, leaving Europe structurally disadvantaged.Footnote 43
The Intermediate-Range Nuclear Forces (INF) Treaty
The INF Treaty, signed in Washington on 8 December 1987 by the United States and the Soviet Union, eliminated all land-based ballistic and cruise missiles with ranges between 500 and 5,500 kilometres.Footnote 44 Although Europe was not a formal negotiating party, it was the treaty’s principal geographic beneficiary – and subject.Footnote 45 The legal structure of the INF Treaty effectively removed an entire class of weapons from European territory, significantly reducing escalation risks.Footnote 46 However, it also entrenched a strategic arrangement in which decisions about nuclear deterrence in Europe were made externally. European states accepted this framework enthusiastically, viewing it as a cornerstone of peace and stability.Footnote 47
The missiles eliminated under the INF regime were not abstract instruments of global deterrence. They were weapons designed for use on European territory, against European targets, and with Europe as the primary battlefield.Footnote 48 European governments strongly supported the treaty. Yet this support masked a deeper structural reality: that Europe did not control the terms of its own disarmament. Decisions concerning the presence, absence, or return of intermediate-range nuclear forces in Europe were made in Washington and Moscow.Footnote 49 The INF Treaty did more than prohibit deployment. Knowledge ecosystems were eradicated, military doctrines ceased to plan for intermediate-range deterrence, research and development pathways were abandoned, industrial capacity withered, and officer education and strategic culture adjusted accordingly. Over time, INF compliance became embedded as a normative assumption, not merely a legal rule. European states did not preserve hedging options or parallel capabilities. Instead, they adapted fully to a security environment in which escalation management at intermediate ranges was no longer considered a European responsibility.Footnote 50
This adaptation reflected a broader belief that arms control had rendered certain forms of war obsolete, and that strategic stability was now maintained through law, transparency, and trust among major powers. However, the United States retained ultimate authority over nuclear escalation affecting Europe. On the other side, the Soviet Union, later Russia, retained the capacity to recalibrate its posture beyond the European theatre; Europe internalised restraint while outsourcing deterrence. This arrangement functioned as long as reciprocal compliance and political convergence endured. However, it left Europe without the legal or material tools to respond autonomously when those conditions deteriorated.Footnote 51
By the 1990s and 2000s, European political identity had become deeply intertwined with the INF regime. The treaty was seen as not merely a security instrument, but also proof of the success of post–Cold War cooperative security.Footnote 52 When allegations of Russian non-compliance emerged, European reactions reflected this normative investment. Rather than treating the treaty as a strategic bargain subject to revision, many European governments approached it as a normative good to be preserved, even at the cost of growing asymmetry. This dynamic created a form of political lock-in. Europe had structured its security environment around a treaty it neither negotiated nor controlled, and the collapse of which it could neither prevent nor compensate for. The US withdrawal from the INF Treaty in 2019 exposed this vulnerability starkly. With the legal framework gone, Europe lacked indigenous INF-range deterrent capabilities; the political consensus for redeployment was also absent, along with a lack of public legitimacy for such systems.Footnote 53
What had once been a stabilising legal arrangement thus revealed itself as a constitutive constraint: Europe had not merely disarmed. It had also forgotten how to deter at a critical level of escalation. Like the CFE Treaty, the INF Treaty institutionalised European restraint in ways that outlasted its strategic foundations. By abolishing an entire category of weapons without creating European agency over deterrence, it transformed legal compliance into structural dependence, leaving Europe strategically exposed when reciprocity collapsed.
This externalisation had long-term consequences. Europe did not merely benefit from the INF Treaty; it adapted to it.Footnote 54 Military doctrines, research priorities, and industrial capacities were reshaped around the assumption that intermediate-range deterrence was no longer a European responsibility. When allegations of Russian non-compliance emerged in the 2010s, Europe found itself politically invested in preserving a treaty it did not control.Footnote 55 The US withdrawal from the INF Treaty in 2019, following Russia’s deployment of the 9M729 missile system, exposed the fragility of Europe’s reliance on bilateral great-power agreements.Footnote 56 Europe lacked both the legal agency and the material capacity to compensate for the treaty’s collapse, reinforcing perceptions of vulnerability.Footnote 57
The Nuclear Non-Proliferation Treaty (NPT)
The NPT,Footnote 58 opened for signature in 1968 and entering into force in 1970, constitutes the cornerstone of the global nuclear order. Its legal architecture establishes a permanent distinction between nuclear-weapon states and non–nuclear-weapon states, codifying inequality in exchange for promises of disarmament, peaceful nuclear cooperation, and security assurances.Footnote 59 For Europe, the NPT had profound strategic implications.Footnote 60 With the exception of France and the United Kingdom, European states accepted permanent non-nuclear status and renounced independent nuclear deterrence. In return, they relied on extended deterrence arrangements under NΑTO, effectively outsourcing ultimate security guarantees to the United States.Footnote 61 Legally, this arrangement was voluntary. Normatively, it became constitutive. Over time, nuclear restraint was not merely a legal obligation but also a marker of European identity as a responsible international actor. Research, development, and doctrinal debates concerning nuclear weapons were marginalised or stigmatised, reinforcing dependence.Footnote 62 The NPT’s disarmament pillar, enshrined in Article VI, has remained largely unfulfilled.Footnote 63 While Europe complied strictly with its obligations, nuclear-weapon states modernised their arsenals.Footnote 64 This asymmetry became increasingly visible in the context of renewed great-power competition, raising questions about whether legal compliance had translated into strategic exposure.Footnote 65
Unlike the CFE and INF Treaties, which were geographically bounded and temporally contingent, the NPT established a permanent legal hierarchy in the international security order. Its central innovation was not disarmament but rather differentiation, that is, the codification of unequal rights and obligations through the possession of the ultimate instrument of deterrence. The NPT formally recognised five nuclear-weapon states – China, France, the Soviet Union (now Russia), the United Kingdom, and the United States – defined by their possession of nuclear weapons prior to 1 January 1967. These states retained the legal right to maintain and modernise their arsenals, subject only to the aspirational commitment in Article VI to pursue negotiations on disarmament. All other sigNΑTOries accepted a permanent renunciation of nuclear weapons, coupled with intrusive safeguards administered by the International Atomic Energy Agency (IAEA). In legal terms, this distinction was voluntary. In political terms, it was the product of intense diplomatic pressure exercised by the dominant powers of the Cold War. The treaty thus created a system in which security was universalised rhetorically but privatised materially.Footnote 66
With the exception of France and the United Kingdom, both of which insisted on maintaining independent nuclear deterrents, European states acceded to the NPT as non–nuclear-weapon states. This choice was not made in a vacuum. During the Cold War, the United States and the Soviet Union exerted strong influence to ensure that no additional European nuclear powers emerged. West Germany, in particular, was subject to sustained pressure and reassurance mechanisms designed to prevent nuclear acquisition while anchoring its security firmly within NΑTO’s extended deterrence framework. For European states, the bargain was clear: renounce sovereign nuclear capability, accept permanent legal restraint, and rely on US nuclear guarantees embedded in alliance structures. Over time, this arrangement became normalised. Nuclear abstinence was not merely a legal obligation but also a moral and political identity marker, closely tied to Europe’s self-conception as a post-military, rule-based actor.Footnote 67
The asymmetries of the NPT regime became most visible after the dissolution of the Soviet Union. Ukraine, Belarus, and Kazakhstan inherited significant nuclear arsenals despite not being recognised as nuclear-weapon states under the treaty. Ukraine’s case is particularly instructive. Possessing the world’s third-largest nuclear arsenal in 1991, Ukraine faced sustained international pressure, primarily from the United States and Russia, to relinquish its nuclear weapons and accede to the NPT as a non–nuclear-weapon state. This pressure was justified in legal and normative terms: nuclear proliferation was framed as incompatible with global stability, while security assurances were offered as substitutes for sovereign deterrence. Ukraine’s accession to the NPT in 1994 thus represented a paradigmatic instance of coercive socialisation into the non-proliferation regime.Footnote 68 While Ukraine and European states internalised nuclear restraint, other states, confronted with hostile security environments, reached different conclusions. At least four states – India, Pakistan, Israel, and North Korea – either refused to join the NPT as non–nuclear-weapon states or withdrew from it altogether. Their reasoning was strikingly consistent: security assurances were politically reversible, alliances were contingent, and legal commitments lacked enforcement. In each case, nuclear weapons were viewed as not destabilising instruments but rather ultimate guarantors of regime survival and territorial integrity. The fact that none of these states has suffered large-scale external military intervention since acquiring nuclear capabilities reinforced this perception.Footnote 69
Russia’s annexation of Crimea in 2014 and its full-scale invasion of Ukraine in 2022 profoundly altered the meaning of the NPT bargain for Europe. Ukraine had complied fully with its non-proliferation obligations, relinquished its nuclear arsenal, and relied on political assurances grounded in international law. Yet when those assurances were violated, no nuclear-armed guarantor intervened militarily to restore Ukraine’s security position. This experience has fuelled a growing, if often implicit, counterfactual: that Ukrainian possession of nuclear weapons would have raised the threshold for Russian aggression. While such claims cannot be proven empirically, they are consistent with deterrence theory and comparative experience. The implication is not that nuclear proliferation is desirable, but that the costs of nuclear abstinence have been unevenly distributed.Footnote 70 For Europe, the NPT functioned as not simply a legal instrument but also a constitutive constraint shaping strategic imagination. By delegitimising nuclear debate and marginalising sovereign deterrence, the regime reinforced dependence on external guarantees – primarily those of the United States. As long as extended deterrence was credible and reciprocal, this arrangement appeared stable. As those guarantees have become politically contested, Europe has found itself legally compliant yet strategically exposed.
Taken together, the CFE Treaty, INF Treaty, and NPT did more than regulate weapons; they reshaped how Europe understood security. Military power was de-emphasised, legal commitments were internalised, and strategic autonomy was subordinated to alliance-based assurances. This was not imposed coercively but rather embraced as the logical extension of Europe’s post-war transformation. However, the durability of this model depended on reciprocal compliance and credible guarantees. As Russia violated or withdrew from arms control regimes and the United States signalled ambivalence towards long-standing commitments, Europe’s legally disciplined restraint increasingly resembled strategic vulnerability.Footnote 71 This legacy explains why contemporary calls for European rearmament face not only budgetary and political obstacles but also deep-seated legal and normative inhibitions. Europe must now confront the paradox of a security identity built on law in an environment where law is no longer reliably enforced.
The tectonic shift (Zeitenwenden)Footnote 72 and the collapse of the normative/value-based order impacting European security architecture and its strategic posture
The Russian invasion of Ukraine represents the most consequential breakdown of the post–Cold War security settlement in Europe and beyond. It is not merely a geopolitical crisis but also a legal and normative rupture that exposes the limits of security assurances in a system premised on restraint and trust.Footnote 73 The gradual strategic shifts observable today in both Germany and Japan further illustrate the extent to which post–Cold War restraint had become deeply institutionalised within major advanced industrial democracies. In Germany, long-standing preferences for multilateral diplomacy, economic statecraft, and military caution – closely associated with the notion of ‘civilian power’ – contributed to persistent reluctance towards large-scale military expansion even after the end of the Cold War. Similarly, in Japan, post-war strategic restraint remained embedded not only politically but also constitutionally through Article 9 and the broader Yoshida Doctrine, prioritising economic development under the umbrella of American security guarantees. Yet the deterioration of the international security environment, particularly following the return of major geopolitical rivalry, has increasingly challenged these assumptions in both states. Germany’s announcement of a Zeitenwende following Russia’s invasion of Ukraine and Japan’s expanding defence posture, including the reinterpretation of constitutional constraints and acquisition of counter-strike capabilities, reflect broader efforts to adapt to a security environment in which cooperative interdependence and institutional restraint are no longer perceived as sufficient guarantees of stability. These developments underscore this article’s broader argument that post–Cold War strategic restraint was not merely a temporary policy preference but instead a deeply embedded normative and institutional paradigm, the gradual erosion of which now carries significant strategic consequences.Footnote 74
Ukraine’s experience is central to this article’s argument because it demonstrates, in concrete terms, how compliance with arms control and non-proliferation regimes, encouraged and facilitated by major powers, failed to translate into durable security. Following the dissolution of the Soviet Union in 1991, Ukraine found itself in possession of the world’s third-largest nuclear arsenal, including approximately 1,900 strategic nuclear warheads and a significant number of delivery systems.Footnote 75 Although operational control remained complex and partially centralised in Moscow, Ukraine nonetheless possessed substantial leverage in the emerging post-Soviet security order.Footnote 76 The international community, led by the United States and Russia, viewed Ukrainian nuclearisation as incompatible with the objectives of the NPT and broader global non-proliferation norms. Ukraine acceded to the NPT as a non–nuclear-weapon state in 1994, a decision that was politically framed as a contribution to international peace and legally anchored in a set of security assurances.Footnote 77 The Budapest Memorandum on Security Assurances, signed on 5 December 1994 by Ukraine, the Russian Federation, the United States, and the United Kingdom, occupies an ambiguous position in international law.Footnote 78 It is not a treaty in the formal sense and lacks enforcement mechanisms.Footnote 79 Nevertheless, it contains explicit commitments to respect Ukraine’s independence, sovereignty, and existing borders, and to refrain from the threat or use of force against its territorial integrity.
From a doctrinal perspective, the Memorandum exemplifies the distinction between legally binding guarantees and political assurances. While its language mirrors core principles of the UN Charter, particularly Article 2(4),Footnote 80 it does not create collective defence obligations analogous to NΑTO’s Article 5. This distinction proved decisive.Footnote 81 Russia’s annexation of Crimea in 2014 and its full-scale invasion of Ukraine in 2022 constituted clear violations of the commitments articulated in the Budapest Memorandum, as well as of peremptory norms of international law.Footnote 82 The absence of automatic enforcement mechanisms, however, rendered these breaches politically condemnable but legally under-deterred. The responses of the other sigNΑTOries – diplomatic protests, targeted sanctions, and political support – fell short of restoring the security position Ukraine had relinquished under the Budapest Memorandum. This outcome has had profound systemic consequences, signalling that security assurances, even when solemnly declared, may not substitute for hard guarantees anchored in enforceable treaty obligations. Scholars have noted that such reliance on political commitments exposes states to strategic vulnerability when coercive actors disregard norms, underscoring the limits of assurances absent robust enforcement mechanisms.Footnote 83 The question of whether Ukraine would have been more secure had it retained nuclear weapons is deeply uncomfortable but unavoidable. While counterfactuals must be approached cautiously, the deterrence logic underpinning nuclear weapons suggests that possession would have significantly raised the costs of aggression.Footnote 84
Ukraine’s fate has reshaped European threat perceptions. It has demonstrated that territorial conquest has returned to the continent and that legal commitments alone cannot prevent revisionist aggression. For Europe, whose own security posture was constructed around similar assumptions of restraint and guaranteed protection, the Ukrainian case functions as a warning. The analogy between Ukraine and the European Union is not exact. EU member states benefit from NΑTO’s collective defence and deeper institutional integration. Yet the underlying logic is comparable: trust in a rule-based order, reliance on external guarantees, and the belief that war had been relegated to history. Ukraine shows how quickly those assumptions can collapse. The collapse of the Budapest assurances has accelerated debates within Europe about strategic autonomy, defence investment, and the credibility of extended deterrence. These debates are not a rejection of international law but rather a response to its selective enforcement.Footnote 85 For Europe, the challenge is to strengthen its security capacity without abandoning the legal and normative framework that defines it. Ukraine’s experience underscores the need to move from a model of passive reliance towards one of shared responsibility and credible deterrence within alliances.
The shockwaves generated by Russia’s aggression against Ukraine have been compounded by a parallel source of uncertainty: the conduct and rhetoric of the United States under the Trump administration. While US pressure on European allies to increase defence spending addressed a real imbalance within NΑTO, the methods and language employed, particularly suggestions of territorial acquisition and coercive leverage, have raised profound legal and normative concerns.Footnote 86 This section argues that these developments represent not mere diplomatic friction but rather a challenge to the foundational principles of the transatlantic order. For decades, the United States functioned as the strategic guarantor of European security, embedding its leadership within a framework of law, institutions, and shared values. NΑTO was not merely a military alliance but also a political community premised on mutual trust and predictability. President Trump’s approach marked a departure from this tradition, reframing alliance commitments as transactional arrangements contingent upon financial contributions.Footnote 87 From a legal standpoint, this shift matters. NΑTO’s North Atlantic Treaty does not condition collective defence on defence spending benchmarks. Article 5 establishes a commitment triggered by armed attack, while Article 3 encourages capacity-building but does not impose quantified obligations. By conflating political targets, such as the benchmarks of 2 per cent or proposed 5 per cent of GDP, with legal duties, US rhetoric blurred the distinction between law and policy.Footnote 88
President Trump’s renewed interest in acquiring Greenland, a self-governing territory within the Kingdom of Denmark, represented a moment of acute normative dissonance. Although framed at times as a commercial transaction, suggestions that economic or political pressure could be used to compel transfer raised alarms in Europe.Footnote 89 Under contemporary international law, the acquisition of territory is governed by strict principles derived from the UN Charter and customary law.Footnote 90 The prohibition of the threat or use of force against territorial integrity, enshrined in Article 2(4) of the UN Charter, applies to not only military action but also coercive practices that undermine sovereign consent.Footnote 91 While peaceful territorial change is not categorically prohibited, it requires the genuine and freely expressed will of the peoples concerned.Footnote 92 Greenland thus became a symbol, not because annexation was likely, but because the discourse itself challenged assumptions Europeans had internalised: that territorial integrity within the transatlantic space was beyond question.
International law draws a sharp distinction between voluntary agreement and coerced consent. The Vienna Convention on the Law of Treaties renders agreements void if procured by the threat or use of force. While Trump’s statements did not culminate in formal legal acts, they contributed to an atmosphere in which power politics appeared to reassert themselves even among allies.Footnote 93 For European audiences, this was deeply unsettling. It suggested that the norms Europe had embraced – sovereignty, non-coercion, and legal equality – might no longer be uniformly respected, even within the alliance that had underwritten European security for generations.Footnote 94 European leaders responded by articulating a growing sense of systemic rupture. At the 2026 World Economic Forum in Davos, European Commission President Ursula von der Leyen publicly questioned whether the world was undergoing a permanent transformation of the international order – one that would require Europe to rethink its strategic assumptions.Footnote 95 French President Emmanuel Macron echoed these concerns, warning of a shift towards a world governed by the rule of the strongest rather than by rules and mutual commitments.Footnote 96 These statements were not rhetorical flourishes. They reflected a recognition that Europe’s security environment was changing simultaneously on two fronts: external revisionism from Russia and internal uncertainty within the transatlantic partnership.
President Macron’s communications to President Trump, portions of which were made public, captured a deeper crisis of mutual understanding.Footnote 97 Macron emphasised that European restraint and reliance on NΑTO were not signs of weakness but rather expressions of trust in shared commitments. The implication was clear: Europe had organised its security posture around US guarantees because those guarantees had been presented as reliable and enduring.Footnote 98 The erosion of that understanding risks producing a self-fulfilling prophecy. If Europe is treated as weak and unreliable, it may be compelled to act in ways that fragment rather than strengthen the alliance. The Greenland episode and broader US rhetoric illustrate how quickly norms can erode when power is foregrounded over law. For Europe, which has internalised legal constraint as a strategic identity, such erosion is particularly destabilising.Footnote 99 This does not negate the legitimacy of US demands for greater European responsibility. It does, however, underscore that coercion, even rhetorical, undermines the very order that made European restraint possible. A stronger Europe cannot be built through threats or humiliation, only through reaffirmation of commitments and shared legal principles.
Debates over Europe’s alleged weakness have increasingly centred on defence spending metrics, most prominently the NΑTO guideline that allies should aim to spend at least 2 per cent of GDP on defence. Under the Trump administration, this benchmark was elevated from a political aspiration to a quasi-moral and rhetorical litmus test of alliance credibility, later supplemented by proposals for even higher targets. While disparities in defence investment are real, this section argues that spending figures alone misdiagnose the roots of Europe’s strategic posture and obscure the legal and institutional context in which European defence policy evolved.Footnote 100 The North Atlantic Treaty of 1949 establishes a collective defence framework grounded in both solidarity and sovereign discretion. Article 5 obliges parties to consider an armed attack against one as an attack against all, but it carefully preserves national constitutional processes by allowing each member to determine the form of assistance it deems necessary. This flexibility was designed to accommodate diverse political systems and strategic cultures. Article 3, often overlooked in public debate, commits parties to developing and maintaining their individual and collective capacity to resist armed attack. Crucially, however, it does not specify quantitative benchmarks or spending thresholds. Defence investment levels have therefore always been a matter of political coordination rather than legal compulsion. The transformation of the 2 per cent guideline into a perceived legal obligation reflects a conflation of treaty law with alliance policy.Footnote 101
The academic literature on NΑTO burden-sharing frequently invokes the concept of free-riding, suggesting that European allies rationally underinvested in defence while benefiting from US protection. While this logic captures part of the picture, it fails to account for the legal and normative environment that encouraged European demilitarisation.Footnote 102 European states did not simply choose to underinvest; they restructured their security priorities in line with arms control commitments, confidence-building measures, and the expectation that major interstate war on the continent had been rendered obsolete. US leadership actively supported this transformation, presenting NΑTO as a stabilising umbrella under which Europe could integrate economically and politically.Footnote 103 It is undeniable that reduced spending produced capability gaps, particularly in areas such as strategic lift, intelligence, missile defence, and high-intensity warfare. Yet these gaps are not merely financial; they are also institutional and doctrinal. Decades of reliance on US enablers shaped procurement choices, force structures, and military planning across Europe.Footnote 104 From a legal–institutional perspective, this outcome was predictable. Arms control regimes limited force levels; non-proliferation norms constrained strategic deterrence; and alliance assurances reduced the perceived need for redundancy. Europe optimised for stability under law, not autonomous power projection.
President Trump’s insistence that Europe must spend more on defence was not only legally unfounded but also politically incomplete. Europe does need to invest more in security. However, portraying Europe as irresponsible ignores the historical bargain underpinning the alliance: restraint in exchange for protection, law in exchange for predictability. If Europe now accelerates rearmament, it is not correcting a moral failure but instead adapting to a transformed strategic environment. The danger lies in framing this adaptation as punishment rather than partnership. A more constructive approach would shift the focus from headline spending figures to strategic responsibility. This includes developing credible European capabilities within NΑTO, strengthening the European defence industrial base, and ensuring interoperability without duplication.Footnote 105 Such an approach aligns with both Article 3 of the North Atlantic Treaty and Europe’s emerging discourse on strategic autonomy. It recognises that strength is measured in not solely percentages but also the capacity to deter aggression while upholding alliance commitments.
Conclusion: From legal restraint to strategic agency
The post–Cold War European security order was shaped by not only American strategic predominance and NΑTO-centred security structures but also a broader legal and normative architecture grounded in arms control, cooperative security, multilateral governance, and economic interdependence. While existing scholarship has frequently explained European strategic restraint primarily through alliance dependence and US security guarantees, this article has argued that treaty-based security regimes also exerted constitutive effects upon European strategic culture and defence policy. Legal–security arrangements did not merely regulate military behaviour; they also contributed to reshaping strategic expectations, institutional priorities, and broader understandings of security and interstate conflict across much of Europe.
This article has further demonstrated that these developments unfolded within a broader post–Cold War normative environment characterised by unusually strong confidence in the capacity of international law, institutional cooperation, and economic integration to mitigate geopolitical rivalry. The institutionalisation of cooperative security frameworks involving Russia – including arms control agreements, the transformation of the OSCE, the NΑTO–Russia Council, and broader efforts at political and economic integration – reflected widespread assumptions that European security could increasingly be managed through legal and institutional mechanisms rather than traditional power balancing alone.
These assumptions profoundly shaped European defence policies during the 1990s and early 2000s. Across much of Europe, military retrenchment, reductions in defence expenditure, shrinking force structures, and the declining prioritisation of military–industrial capacity reflected the belief that large-scale interstate war on the continent had become increasingly unlikely. While NΑTO persisted as the principal collective defence framework in Europe, its strategic orientation also evolved towards crisis management, stabilisation missions, and partnership mechanisms, reinforcing broader assumptions concerning the declining centrality of territorial military confrontation within Europe itself.
This article has argued, however, that these legal and normative transformations also generated path-dependent strategic consequences. Over time, military restraint became embedded not only politically but also institutionally and materially, making rapid strategic adaptation increasingly difficult once geopolitical competition re-emerged. Europe’s contemporary strategic vulnerabilities therefore cannot be understood solely as the result of external dependence upon the United States; they are also the long-term consequence of a post–Cold War security paradigm that prioritised legal institutionalisation, cooperative security, and economic interdependence over sustained military preparedness.
At the same time, this article does not suggest that post–Cold War European security arrangements were simply naïve or irrational. Nor does it argue that cooperative security frameworks lacked stabilising effects. For several decades, these arrangements contributed to a historically unprecedented period of relative stability, institutional integration, and reduced interstate military confrontation across much of Europe. The problem, rather, is that the durability of this security paradigm depended upon the continued reciprocity of its principal participants and upon broader geopolitical conditions that proved less permanent than many policymakers had assumed.
The erosion of post–Cold War cooperative security frameworks therefore does not necessarily imply the complete collapse of multilateralism or the inevitable return of classical bloc confrontation. It does, however, challenge many of the assumptions upon which European strategic restraint was constructed. As geopolitical rivalry has intensified and the institutional foundations of cooperative security have weakened, European states increasingly face pressure to reconsider the relationship between legal–security regimes, strategic autonomy, military capability, and deterrence.
In this context, a renewed transatlantic framework grounded in shared strategic commitments may continue to represent an important source of European stability. However, the article does not assume that such a framework is politically inevitable or structurally guaranteed. Rather, the contemporary European security environment suggests that the long-term sustainability of cooperative security arrangements ultimately depends upon not only normative alignment and institutional integration but also the continued credibility of deterrence, reciprocity, and strategic capacity within the broader Euro–Atlantic order.
Besfort Rrecaj is an associate professor of law at the University of Prishtina Faculty of Law, focusing on international law and relations. He teaches courses on international treaties, international relations theory, international organisations and the EU’s CFSP at the bachelor’s and master’s level. He was educated at the State University of New York (LLM), the University of Prishtina (PhD), George C. Marshall European Center for Security Studies and of the Vienna Diplomatic Academy.
Acknowledgements
The author wishes to thank the reviewers for their time and concise feedback.
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