Military Realignment and the Cordon Sanitaire: EU Strategic Encirclement and the Western Balkans Security Dilemma

The EU presents its Western Balkans engagement as a partnership built on voluntary convergence and shared democratic values. The military expenditure data tells a different story, one of parallel escalation, differential treatment, and an institutional architecture whose cumulative effect is the strategic isolation of non-aligned states.

The EU’s engagement with its immediate and extended periphery increasingly reflects a structured logic of buffer-zone management, through which economic integration, normative conditionality, and, progressively, military cooperation are deployed as mutually reinforcing instruments of geopolitical containment.

The convergence of the U.S.-Israeli military operation against Iran, the conflict in Ukraine, and the rising tensions in the Western Balkans, driven predominantly by the contrasting orientations of the EU and Serbia, alongside longstanding inter-state disputes in the region, collectively illustrate what has been conceptualised as a cordon sanitaire: a system of alliances historically designed to ideologically isolate and contain a rival power (Wisdom Library, 2025). In its 21st-century form, this strategy operates through economic sanctions, political conditionality, normative frameworks, and selective economic and political favouritism rather than through formal military pacts alone.

As the Heinrich Böll Stiftung has noted in the context of Iran, this approach has repeatedly proven “toothless” when confronted with determined state resistance, revealing a structural capability-action gap (Heinrich Böll Stiftung, 2024). Iran and Ukraine are not incidental references but instructive precedents. In both cases, the EU deployed an identical operational sequence of economic pressure, normative framing, and military instruments, and in both cases, the limits of that sequence were exposed when the targeted actor refused alignment.

The Western Balkans represents the most institutionalised and geographically proximate application of this same model, and its dynamics must be read in that broader context. More recent scholarship further suggests that the EU’s reliance on economic sanctioning and its failure to sustain independent commitments, as demonstrated by the trajectory of the JCPOA framework, risk eroding its credibility as a strategic actor when engaging in conflicts beyond its immediate neighbourhood (Nicu, 2026).

The application of the cordon sanitaire concept to the contemporary EU-Western Balkans dynamic requires explicit theoretical grounding, as the historical usage, denoting a formally coordinated alliance architecture designed to contain Soviet influence in interwar Europe, differs structurally from what this analysis identifies.

The argument advanced here is not that the EU has declared or designed an encirclement policy, but that the cumulative institutional architecture it has constructed produces containment-like effects on non-aligned states through mechanisms that Susan Strange identifies as structural power: the capacity to shape the framework of choices available to other actors without the need for direct coercive instruction (Strange, 1988).

Ian Manners’ formulation of EU normative power characterises the Union’s ability to define what is normal in international relations through the diffusion of norms rather than through material force, and has been widely employed to frame EU external engagement as inherently benign and transformative (Manners, 2002). The critical underside of this formulation, however, is that normative diffusion, backed by conditional access to economic and institutional frameworks, constitutes a form of structural coercion against states that refuse the terms of normalisation.

When applied to states within the EU’s immediate neighbourhood with sufficient consistency and directionality, this mechanism warrants the cordon sanitaire designation as an analytical heuristic, not as a claim about declared intent, but as a characterisation of structural effect. The distinction is analytically significant: it shifts the burden of the argument from demonstrating EU intentionality to demonstrating the patterned outcomes that the EU’s institutional architecture produces, which the evidence examined in this paper supports.

This broader pattern of EU conduct is directly observable in its management of the Western Balkans. As the EU’s largest external investor in the region (Nicu, 2025), the Union has deployed economic leverage as the primary mechanism of political conditioning while simultaneously demonstrating a pattern of differential treatment that favours aligned states regardless of comparable governance shortcomings.

The accelerated accession trajectories of Albania, Montenegro, and North Macedonia, and the preferential engagement extended to Kosovo, persist despite institutional and governance challenges broadly comparable to those documented in the 2024 EU Progress Report on Serbia (European Commission, 2024). The selectivity of this engagement undermines the normative coherence of the EU’s enlargement framework and reinforces the perception, particularly in Belgrade, that the conditionality architecture is applied instrumentally rather than uniformly.

Semenov’s analysis of the structural deterioration of EU legitimacy in the Western Balkans identifies four constitutive features of this dynamic: the overestimation of superficial reforms that do not substantively restructure domestic governance; a deliberate prioritisation of stability over democratic consolidation; the progressive erosion of EU negotiating principles through bilateral vetoes; and the persistent internal crisis within EU institutions that limits the Union’s capacity for sustained regional engagement (Semenov, 2024).

These are empirical observations about structural pattern. The normative question of whether this pattern is legitimate relative to the EU’s own stated commitments to democratic values and rule-based conditionality requires a separate standard of evaluation, and the EU’s own enlargement framework provides it: the principle that accession progress must be merit-based, transparent, and applied uniformly across candidate states (European Commission, 2025).

Measured against this declared criterion, the differential treatment documented above constitutes an internal inconsistency within the EU’s own framework rather than merely an externally imposed objection. The cumulative effect of what might be characterised as an “ends justify the means” approach is twofold: it erodes the EU’s credibility as a norm-based actor, and it actively generates regional tensions by making EU support visibly contingent on political alignment, a dynamic that non-aligned states readily interpret as an externally imposed hierarchy of legitimacy.

The stalled economic integration of the Western Balkans Six, a process that has required selective reinvestment and repeated extensions of the accession timeline, and the simultaneous intensification of military cooperation among NATO member states in the region raise substantive questions about the nature of the power-balancing process currently underway. The shift in emphasis from civilian integration instruments to security architecture suggests that the EU and its partners are increasingly managing the Western Balkans as a strategic perimeter rather than a prospective community of equals.

This militarisation of EU peripheral strategy is not confined to the Balkans. As of 2024, EU-27 defence expenditure reached EUR 343 billion, more than three times Russia’s reported EUR 107 billion and exceeding China’s EUR 250 billion, with only the United States surpassing it at approximately EUR 845 billion (European Parliamentary Research Service, 2025).

Instruments such as the European Defence Fund and the European Peace Facility extend EU defence activity beyond conventionally defined defensive parameters, a trajectory most visible in the case of Ukraine, where combined EPF and Member State military support has reached EUR 63.2 billion (European Parliamentary Research Service, 2025). Becker and Kempin’s assessment that European intelligence services regard a Russian conventional attack on Europe as a realistic prospect within five years, as of 2025, provides the strategic rationale underpinning the Readiness 2030 initiative and the proposed SAFE instrument, which are in part responses to the compounding pressures of perceived threat and reduced U.S. burden-sharing (Becker and Kempin, 2025).

Taken together, the EU’s documented posture in Eastern Europe and the military presence it maintains in the Balkans through Member States, NATO structures, and the EUFOR-Althea mission since 2004 support the interpretation that the Western Balkans is managed not solely as a partner region but as a component of a broader geopolitical encirclement strategy, in which buffer-zone maintenance and capability expansion operate in parallel.

Figure 1 illustrates this dynamic in empirical terms. The data reveals a pattern of parallel escalation in military expenditure as a share of GDP across Western Balkan states, with Serbia maintaining the highest sustained level throughout the observation period and all NATO-aligned states demonstrating a consistent upward trajectory.

The anomalous flatness of Bosnia and Herzegovina’s expenditure curve, consistently below 0.75% of GDP across 2020-2024, requires contextualisation. The EUFOR-Althea operation, EU-led since 2017 and renewed by UNSC resolution for a further 12 months in 2025, has contributed to suppressing the development of autonomous Bosnian defence capabilities. This effect must nonetheless be read alongside the country’s structural constitutional paralysis, given that entity-level budgetary disputes and fragmented defence competencies independently constrain coherent security policymaking (SHAPE NATO, n.d.).

The renewal of UNSC Resolution 2795 (2025) authorizing EUFOR-Althea is embedded within broader debates over the legitimacy of international governance in Bosnia and Herzegovina. While the resolution itself was adopted unanimously, political contestation persists at the level of interpretation.

The Greek representative’s assertion that “the future of Bosnia and Herzegovina is intertwined with the European Union”, articulated against a backdrop of acute internal division, stands in contrast to Serbian officials’ characterization of the Office of the High Representative as having “replaced democratic legitimacy with political imposition, while claiming to ensure functionality” (United Nations Security Council, 2025). The latter framing raises questions regarding the continued applicability of the Thessaloniki Declaration of 2003, whose premise of shared democratic values as the foundation for EU-Western Balkans engagement appears increasingly difficult to reconcile with the current political configuration in Bosnia and Herzegovina.

The consolidation of Republika Srpska’s political orientation further complicates the EU’s positioning. The victory of Siniša Karan, candidate of Milorad Dodik’s SNSD and confirmed through repeated ballots, was met by a Russian Foreign Ministry statement affirming that “the citizens of that entity rose against the distortion of their will and reaffirmed their strong support for the patriotic policy of Milorad Dodik’s team”, and that continued partnership with Republika Srpska “fully meets the interests of the peoples of the Russian Federation and Republika Srpska” (Ministry of Foreign Affairs of the Russian Federation, 2025). Serbia’s role as a kin state providing political and rhetorical support for Serb minorities across the Western Balkans amplifies this dynamic and places additional pressure on the EU’s narrative of convergence in the region.

Figure 2 provides the quantitative dimension of this analysis, covering the 2016-2024 period. Serbia registers the highest individual military expenditure of any single state in the region across the entire window.

The combined spending of the region’s four NATO members, Croatia, Albania, North Macedonia, and Montenegro, has nonetheless exceeded Serbia’s in every year from 2020 to 2024, with the margin ranging from $66.8M in 2021 to $420.7M in 2023 and settling at $345.5M in 2024. Croatia constitutes the dominant share of this aggregate, while Albania recorded the most pronounced rate of change, with an increase of over $137M between 2023 and 2024 alone.

Figure 3 reveals a further dimension: Albania surpassed Serbia in the share of government expenditure allocated to defence in both 2023 (5.97% vs. 5.44%) and 2024 (6.61% vs. 6.05%), reflecting a domestic political prioritisation of military capacity that extends beyond raw budget size.

Serbia retains a higher defence-to-GDP ratio across the full period, at 2.21% against Albania’s 1.74% in 2023 and 2.60% against 2.04% in 2024, indicating that its overall defence commitment remains larger in macroeconomic terms. Croatia, despite holding the largest GDP in the region as of 2024, has maintained defence spending consistently below 2% of GDP throughout the observation window, placing it among the lower-performing NATO members by this measure, while exhibiting an upward trend in absolute terms.

Figure 4 distils the 2024 snapshot into a direct proportional comparison of military expenditure in current USD across all Western Balkan states. The distribution confirms what the trend data in Figures 2 and 3 establishes across time: Serbia accounts for the largest individual share at $2,322,830,101.6, while the four NATO-aligned states collectively constitute a larger combined share at $2,668,246,349.8, with Bosnia and Herzegovina occupying a marginal position at $215,974,888.5 that reflects its externalised defence posture rather than any domestic strategic calculus.

Read alongside the trend data, this snapshot reinforces the structural argument: the proportional weight of NATO-aligned expenditure in the region is not a recent development but the consolidated outcome of the upward trajectories visible across the full observation window.

Montenegro provides the clearest available test case for the incentive architecture this analysis describes, and the evidence warrants careful treatment because it neither straightforwardly confirms nor refutes the cordon sanitaire thesis.

As the EU’s self-designated frontrunner in Western Balkans accession, having opened all 33 negotiating chapters by 2021 and provisionally closed 14 by early 2026, Podgorica’s trajectory demonstrates that sustained alignment with EU conditionality generates tangible institutional rewards: accelerated chapter closures, access to the Reform and Growth Facility, and a formal Commission acknowledgment that accession is “increasingly within reach” (New Union Post, 2025a). The incentive architecture functions as the EU’s enlargement framework describes.

What the Montenegro case also reveals, however, is that those rewards are themselves permanently conditional and structurally asymmetric. Despite being designated the regional frontrunner, Montenegro operates under continuous monitoring of Chapters 23 and 24, faces post-accession safeguard discussions for which earlier enlargements provide no direct precedent, and its domestic reform environment remains characterised in the Commission’s own 2025 assessment by fragile rule-of-law institutions, contested judicial appointments, and declining public support for EU membership (New Union Post, 2025b).

The French veto on two chapter closures in December 2025, resolved only through last-minute diplomatic pressure, illustrates a further dimension of this asymmetry: alignment does not eliminate bilateral leverage within the EU system but relocates it from the accession gateway to the negotiating table itself, where individual member state interests can interrupt the process irrespective of the candidate’s reform record.

Montenegro thus confirms that the EU’s incentive architecture rewards compliance with real but never unconditional access, producing a model of managed integration that never fully resolves the structural asymmetry between the EU as rule-setter and the candidate state as permanent rule-taker. For Serbia, observing this dynamic from outside, Montenegro’s position represents not an unambiguous advertisement for alignment but a precise demonstration of the terms on which alignment is offered and the costs to sovereignty that it entails.

These expenditure patterns carry direct implications for the political configurations that emerged in 2025. Bechev and Gjoni’s analysis for Carnegie Europe, published in October 2025 and drawing on precisely the period captured in Figures 1-4, argues that Albania, North Macedonia, and Montenegro are positioned to play a leading role in regional defence integration, while Serbia’s neutrality, characterised as a “multivector foreign and security policy” involving military procurement from Russia and China, means that broader “cooperation will face obstacles”.

The same analysis notes that “the Western Balkans is home to roughly 200 companies in the defence sector, located primarily in Serbia and Bosnia” (Bechev and Gjoni, 2025). The expenditure data presented here thus functions as a leading indicator: the trajectories observed between 2020 and 2024 translated directly into the strategic assessments and political tensions that Bechev and Gjoni document in 2025, establishing the causal connection this analysis sets out to identify.

In all four figures, Bosnia and Herzegovina’s position is visually and analytically distinct. Its near-linear flatness across a decade reflects a state whose defence posture has been effectively externalised through the EUFOR-Althea framework, leaving it simultaneously stable and contested, and subject to criticism that its domestic arena has been structured to serve the enlargement interests of external actors rather than the sovereign preferences of its population.

The establishment of a non-binding trilateral alignment between Croatia, Albania, and Kosovo in early 2025 sharpened these tensions considerably. Serbia’s response framed Croatia, Bulgaria, and Albania as “historical enemies” acting against Serbian state interests, with diplomat Zoran Milivojevic characterising these states as having “mainly served the big powers to suppress Serbia’s interests in this region”, and Bulgaria and Croatia as “obviously doing this under the influence of Germany” (BGNES, 2024).

This is analytically notable less for its evidentiary basis, which remains absent, than for what it reveals about the domestic narrative function of regional isolation. The cancellation of the Brdo-Brijuni summit by Croatian President Milanović, who stated that “under such circumstances, conditions do not exist for Vučić to visit Croatia”, a verdict Vučić himself endorsed with the reply, “He is absolutely right, I don’t belong there” (Euractiv, 2025), is a concrete illustration of how diplomatic exclusion by states already embedded in EU and NATO structures reinforces Serbia’s strategic incentives to maintain its non-aligned posture rather than accommodate further conditionality.

The systematic exclusion of Serbia from regional formats that its neighbours participate in precisely by virtue of their alignment with extra-regional organisations to which Serbia does not belong, or does not belong to the same extent, echoes and amplifies the EU’s own approach to Serbian grievances.

The collective effect of these dynamics is to foreclose the diplomatic space within which Serbia might otherwise recalibrate its positioning, reinforcing rather than dissolving the structural conditions that sustain its neutral stance. The Montenegro comparison further clarifies why Belgrade calculates as it does: the rewards of alignment are real, but they arrive in a framework that permanently subordinates sovereign policy space to EU institutional monitoring and member state veto power, a trade-off that Serbia’s current domestic political configuration renders particularly costly to accept.

Conclusion

The evidence presented across this analysis supports the argument that the EU’s engagement with the Western Balkans operates within a strategic framework that is functionally consistent with the management of a cordon sanitaire, understood in the analytical sense established above: not as a declared encirclement policy but as an institutional architecture that produces containment-like structural effects on states that refuse alignment.

The military expenditure data for 2020-2024 makes this dynamic legible in quantitative terms. The combined spending of NATO-aligned states in the region has consistently exceeded Serbia’s across the entire period, while Serbia’s own defence expenditure, the highest as a share of GDP of any country in the group, reflects the compounding strategic pressure generated by this alignment gap. Bosnia and Herzegovina’s anomalous expenditure stasis, maintained below 0.75% of GDP throughout the period, encapsulates the cost of prolonged external management: a state stabilised in form but stripped of the institutional autonomy required to develop an independent security posture.

Montenegro’s trajectory as the EU’s frontrunner candidate simultaneously confirms and complicates this picture. It confirms that the incentive architecture functions: alignment is rewarded with accelerated institutional access. It complicates any straightforward critique of that architecture by demonstrating that those rewards are real and, for a state of Montenegro’s size and strategic position, genuinely significant.

What it does not do is resolve the fundamental asymmetry: the candidate state is permanently positioned as rule-taker within a framework whose terms the EU sets, adjusts, and enforces through mechanisms that individual member states can deploy for bilateral purposes irrespective of reform performance. The argument is therefore not that EU conditionality is fraudulent but that it operates within a structural power relationship whose implications for regional sovereignty and security autonomy are more consequential than the enlargement framework’s normative self-presentation acknowledges.

The precedents established in the EU’s engagement with Iran and Ukraine demonstrate that this operational logic is not regionally specific but reflects a broader pattern of EU strategic behaviour when confronted with non-compliant actors across different geographies and at different distances from its institutional core. As the Heinrich Böll Stiftung’s assessment of the Iran case illustrates, and as the Ukraine trajectory further confirms, coercive conditionality applied against states with strong domestic control apparatuses tends to reinforce resistance rather than produce alignment. This finding has direct relevance for the EU’s continuing engagement with Serbia and, through it, with the wider Western Balkans security complex.

Underlying this entire dynamic is a normative contradiction that the EU has not adequately confronted. The EU’s enlargement framework is premised on voluntary accession driven by genuine sovereign choice. That premise loses its substance when the institutional architecture surrounding it is designed to make non-alignment structurally prohibitive through cumulative economic, political, and security pressure.

A state’s right to determine its own foreign policy orientation, including the right to maintain neutrality or to refuse membership in any particular alliance or integration framework, is not a residual privilege to be conditionally tolerated. It is a foundational principle of sovereign equality grounded in the UN Charter and affirmed in the Helsinki Final Act. The EU is not a state and cannot formally violate these norms, but when its institutional conduct systematically penalises the exercise of that right, it operates in tension with the very principles of self-determination and free association it formally endorses.

This tension is not merely philosophical. It has measurable consequences: it delegitimises the EU’s normative authority among the states it most needs to persuade, produces the regional fragmentation visible in the data examined here, and forecloses the cooperative prospects that a genuine partnership framework would make possible.

A revision of this approach is not only warranted on principled grounds. It is a practical necessity for any credible EU strategy toward the Western Balkans. The region’s long-term stability, and the EU’s own credibility as a regional actor, depend less on the further tightening of conditionality mechanisms than on the development of an engagement model that treats the sovereign choices of non-aligned states as legitimate inputs rather than obstacles to be managed away.

Concretely, this requires the EU to enforce its own normative standards uniformly across candidate states regardless of their alignment preferences, to develop engagement frameworks that accommodate partial or differentiated integration rather than conditioning all cooperation on full accession compliance, and to accept that a regional partner which retains sovereign policy independence is not a failure of EU strategy but a legitimate outcome of the very principles of free choice and democratic self-determination that the Union claims to champion.

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Data Sources

• World Bank, World Development Indicators: Military expenditure (current USD) among Western Balkan countries, World Bank Open Data, 2024. [Online]. Available:  https://databank.worldbank.org/source/world-development-indicators 
• World Bank, World Development Indicators: Military Expenditure (% of GDP) and Military Expenditure (Current USD), Western Balkans, World Bank Open Data, 2024. [Online]. Available: https://databank.worldbank.org/source/world-development-indicators
• World Bank, World Development Indicators: GDP (Current US$), Western Balkans, World Bank Open Data, 2024. [Online]. Available: https://databank.worldbank.org/source/world-development-indicators
•  World Bank, World Development Indicators: Military Expenditure (% of GDP) and Military Expenditure (Current USD), Western Balkans, World Bank Open Data, 2024. [Online]. Available: https://databank.worldbank.org/source/world-development-indicators