Böll EU Brief
Phalanx of defence pacts? Mapping bilateral defence partnerships in Europe
Böll EU Brief 05/2025
By Roderick Kefferpütz and Anika Bruck
In the media: Süddeutsche Zeitung, Defence24.com
Key findings:
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Europe’s defence map is being redrawn. Our unique dataset captures over 160 bilateral and plurilateral defence arrangements signed since 2014 betweenEU Member States, UK and Ukraine. Most of these partnerships emerged after Russia’s full-scale invasion, with 2024-2025 alone accounting for more than half.
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Bilateralism brings both strength and strain. These partnerships deepen trust, build interoperability and speed up procurement. They can be a crucial foundation for theEU’s Defence Readiness Roadmap 2030. But they also risk producing duplication, inefficiencies and a fragmented patchwork of commitments.
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Turning bilateralism into strategy is essential. To move from patchwork to phalanx, the EU and NATO should map and monitor agreements, plug them into NATO and EU planning, put them on the NATO- EU agenda, consider the European Defence Agency as a matchmaking hub, raise the minimum participation requirement for EU defence procurement, and use bilaterals to offset declining US support.
Since Russia’s full-scale invasion of Ukraine, security and defence have moved to the very centre of Europe’s political agenda. NATO has sharpened its deterrence posture, and the European Union has launched a range of new defence initiatives, such as the Defence Readiness Roadmap 2030.
Yet beneath this surge of multilateral activity, another trend is reshaping Europe’s security architecture: the proliferation of bilateral defence partnerships. While EU and NATO headquarters attract the spotlight, national capitals remain the decisive arena where governments make core defence choices. It is there that an increasingly dense network of bilateral defence agreements has taken shape.
These reflect both a pragmatic response to a new threat environment and possibly a deeper reconfiguration of Europe’s security architecture. However, the substance of these agreements varies considerably. While some arrangements appear to deliver tangible operational benefits, others remain largely symbolic.
This Böll EU Brief examines this often-overlooked dimension of European security. It presents the results of an extensive mapping exercise, which has identified and categorised over 160 bilateral (and plurilateral) defence arrangements between EU Member States, including their ties with the United Kingdom and Ukraine, from 2014 to 2025.¹
By analysing this unique dataset, the brief traces how these bilateral partnerships have multiplied and evolved, which country acts as a key node, and whether these new arrangements undermine or reinforce the EU’s ambition to become a more coherent defence actor.
It concludes with a number of policy recommendations, on how bilateral partnerships can be channelled into a stronger European defence posture that complements and strengthens EU initiatives, such as the Defence Readiness Roadmap 2030.
Mapping Europe’s bilateral defence ties
Bilateral defence ties have particularly accelerated over the past years (see graph 1). Since Russia’s full- scale invasion in 2022, 135 bilateral partnerships have been signed. This represents 80 per cent of all mapped partnerships between 2014-2025.
With the spectre of a second Trump presidency looming in 2024 and uncertainty over US security commitments in Europe increasing in 2025, these years have seen a veritable surge. They are responsible for slightly over half of all partnerships (57 in 2024, 36 to date in 2025).
These are also the years where significant comprehensive strategic partnerships have been signed, such as the Treaty on friendship and bilateral cooperation between Germany and the UK, and the Treaty on Enhanced Cooperation and Friendship between France and Poland that also includes mutual security guarantees.
Bilateral cooperation in procurement and industrial cooperation has been particularly dynamic. In 2025 alone, almost 20 such agreements were struck, reflecting Europe’s urgency to build up defence production and reduce dependence on the United States.
What emerges is a complex web of partnerships. Some are comprehensive security frameworks covering multiple issues, an increasing number are exclusively focused on the defence industry and joint procurement, including technical standardisation, while others are dedicated to operational matters, including military exercises, operational defence planning and military mobility coordination, or cybersecurity.
Most take the form of formal cooperation agreements or political declarations, though some remain more tentative statements of intent. The highest and most relevant form is a formal strategic partnership, which are respectively limited amongst all the types of partnerships. This mixture of comprehensive agreements and issue-specific cooperation, binding commitments and looser political signals reveals both the experimentation and the momentum shaping Europe’s security order (see graph 2 and 3).
Certain countries stand out as central hubs in this web (see graph 4). France, Germany, Sweden and Finland are at the forefront among EU Member States, each concluding dozens of agreements and cultivating ties across a wide range of partners. France and Germany in particular maintain highly diversified portfolios, each linked to more than twenty other countries.
Smaller states tend to concentrate regionally. Latvia overwhelmingly invests in ties with its Baltic and Nordic neighbours. At the opposite end of the spectrum, neutral states such as Austria, Ireland, and Malta, or countries with a diverging threat perception, such as Hungary, have concluded very few, underlining the extent to which neutrality and, in the case of Hungary their political outlook, limits their embeddedness in Europe’s defence networks.
Regional constellations are especially pronounced in Northern and Eastern Europe. The Nordics form one dense cluster, with Sweden and Finland acting as major nodes. While the Baltic states are deeply interconnected, not only bilaterally but also in minilateral clusters such as joint Home Guard cooperation or collective procurement of HIMARS rocket launchers and CV90 armoured vehicles. Geographical closeness to Russia is a strong factor influencing defence partnerships, with some countries forging closer military ties with France in particular to “compensate for the uncertainty about American security guarantees to Eastern Europe”.²
Beyond the EU, Ukraine and the United Kingdom have become indispensable partners. 21 EU Member States now have a comprehensive defence agreement with Kyiv. The United Kingdom, for its part, has signed 25 bilateral arrangements with 21 EU states, ensuring its continued centrality in European security after Brexit. This proliferation is also rooted in the post-Brexit legal framework: because defence and security fall outside the EU-UK Trade and Cooperation Agreement, London is free to pursue bilateral agreements in this field.
Last but not least, based on an initial analysis of our dataset, there are six partnerships with a mutual defence clause involving France, Finland, Germany, Greece, Poland, Sweden and the United Kingdom. France and the UK lead the pack with three such clauses each, followed by Germany with two. This underlines that mutual defence clauses are still primarily the domain of major European powers.
Taken together, these developments show how the continent’s defence architecture is evolving.
Challenges and opportunities of bilateralism
The proliferation of bilateral defence partnerships is, in many ways, a positive development. They help build trust, deepen interoperability, may reduce costs in military procurement, and can lead to integration of forces like the joint Dutch-Belgian navy or the German-Dutch corps.
At the same time, this surge carries risks. Without coordination, bilateralism can generate duplication, inefficiencies, and a patchwork of commitments with uneven depth. Some agreements are politically performative rather than operationally meaningful, while others may overlap.
The absence of a clear institutional “home” compounds the problem. NATO remains the cornerstone of collective defence in Europe but is shaken by uncertainty about US commitment; the EU, while active on the industrial and capability side, is not a defence actor in the full sense.
Of course, EU frameworks like PESCO provide structure, but bilaterals have a lot of momentum providing speed and scale. And coalitions of the willing, such as those mobilising for Ukraine, can fill a void but lack permanence and institutionalisation.
This creates what one might call a geometry of position; a distributed and sometimes unstable arrangement of partnerships. One way of interpreting this emerging order is through “layering”: bilateral partnerships as one layer, regional groupings as another, EU’s industrial and regulatory power as a third, and NATO as the ultimate collective defence layer.
While NATO with its capability targets lies at the core, the EU can provide incentives for greater coordination through procurement programmes. They can channel bilateral activity into broader European objectives and promote more plurilateral activity with Member States teaming up to access EU programmes such as the SAFE instrument which requires at least two countries to join to participate.
One might ask, however: why is the minimum eligibility just two states, when traditionally EU programmes,such as the European Defence Fund (EDF) and the European Defence Industry Reinforcement through Common Procurement Act (EDIRPA), require at least three? Raising this threshold could more effectively encourage genuine joint procurement.
From patchwork to phalanx
Bilateral partnerships are not a panacea, nor a problem in themselves. They are a symptom of Europe’s search for security amidst geopolitical uncertainty, and they are low-hanging fruit since they are much simpler to reach and faster to implement.
Whether they evolve into a confusing patchwork or a phalanx of defence pacts will depend on whether Europe can muster the imagination, institutional frameworks and programmes to connect and make the most out of them. In this regard, three pillars are be crucial.
1. Map and monitor
The topic of bilateral and plurilateral defence partnerships among EU Member States remains understudied. There is a need to better understand the fast-evolving defence web in Europe. To address this, the EU and NATO should:
• Establish a registry of bilateral defence agreements to help monitor overlaps, identify gaps and share good practices, for example via the European Defence Agency, which is already mandated to map capability development and has data-sharing channels with Ministries of Defence.
• The planned European Defence Semester could provide a structured framework in this regard.
• Put bilateral defence partnerships as an item for discussion in NATO-EU consultations.
2. Connect and coordinate
Bilateralism can strengthen European deterrence if it is connected. To avoid a patchwork of overlapping partnerships, the EU and NATO should hardwire bilateral efforts into collective planning and capability development. This could be facilitated by:
• Having NATO mechanisms in bilateral agreements by clearly designing the defence partnerships so as to make them contribute to allies’ NATO Defence Planning Process (NDPP) targets.
• Turning the European Defence Agency into a matchmaking platform that, together with EU defence support programmes, helps turn bilateral procurement pacts into broader capability constellations. Scazzieri has highlighted the EU’s potential to harness small-group cooperation in this regard.³ A registry of bilateral defence agreements, especially with regards to procurement, could help in the matchmaking function.
• Raising EU procurement thresholds, for example in the SAFE instrument, from two Member States to a minimum of three, to turn bilaterals into trilaterals (or plurilaterals). This would be consistent with other EU-defence instruments (e.g. EDF, EDIRPA).
3. Fill the US gap: bilaterals as a backstop
The US Department of Defense is phasing out several security assistance programmes for European countries bordering Russia, including the Section 333 “train-and-equip” initiative and the Baltic Security Initiative (BSI). At the same time, the ongoing U.S. Force Posture Review has created renewed uncertainty about the long-term shape and scale of the American military footprint in Europe.
Any emerging gap should be filled and it falls above all to Europe’s major actors to step in. Bilateral defence partnerships offer a ready-made, framework to act quickly. Countries such as France, Germany, the UK and Nordics could use their existing bilateral partnerships to augment financial, training and capability support for Eastern frontline states. This could be an effective and timely way to offset shortfalls in U.S. assistance.
Footnotes
¹ This dataset focuses on EU Member States and includes their partnerships with the United Kingdom and Ukraine. The selection reflects the EU’s institutional scope and two additional cases of strategic relevance. The period 2014 to September 2025 was chosen to capture developments since Russia’s annexation of Crimea. The dataset is derived exclusively from desk research and publicly accessible sources. Given that parts of this policy domain are classified, informal, or not fully disclosed, the authors cannot guarantee completeness or full accuracy. The material should therefore be understood as a best-effort mapping, reflecting the most reliable information available at the time of writing. While the dataset includes plurilateral partnerships, our analysis focuses exclusively on bilateral defence partnerships. To help fill any gaps, we have made this dataset publicly available for other researchers to continue work on it: https://eu.boell.org/en/defence-partnerships-europe
² Yf Reykers & Pernille Rieker (2024) Ad hoc coalitions in European security and defence: symptoms of short-term pragmatism, no more?, Journal of European Integration, 46:6, 861-879
³ Scazzieri, Luigi, Rebuilding Europe’s defences: How to unlock a coordinated defence surge, 23 September 2025. https://www.iss.europa.eu/ publications/briefs/rebuilding-europes-defences-how-unlock-coordinated- defence-surge
Acknowledgements
The authors are grateful to Sara Nanni, Ed Arnold, Luigi Scazzieri, Tobias Heider, Tom Köller, Christina Kessler, Katharina Emschermann, Philipp Straub, Georg McCutcheon and Florian Lenner for their insightful comments and constructive feedback. Any errors or omissions are the sole responsibility of the authors.
