The return of great power competition and the weakening of the international order have produced significant threats to Europe’s security. Most urgently, Russia’s aggression has brought large-scale war to Ukraine and Russia into a hybrid confrontation with Ukraine’s western allies. At the same time, the US seems ready to reduce its commitment to Europe’s security and even to be hostile towards its long-standing partners and the values they defend.[1] This deteriorating geopolitical situation should encourage greater synergies between NATO and the EU, the two main organisations that deal with security and defence in Europe.
Download and read as a PDF: Brief 5. The EU-NATO Relationship
While NATO and the EU were created with distinct objectives—collective defence for NATO, and economic and social cooperation for the EU—the fall of the USSR in 1991 somewhat reshuffled the deck. Once the Soviet threat had disappeared, NATO’s raison d’être was questioned and the issue of European defence and the sharing of competences between the US and Europe, which had been avoided during the Cold War, was raised. During the post-Cold War period, the EU became a more political union, introducing a common foreign and security policy at Maastricht in 1993 and, from the mid-2000s, enlarging to the former Eastern Bloc.
After Russia’s illegal annexation of Crimea, NATO and the EU organised themselves to cooperate more closely on security issues
Crises of the period, particularly the conflicts in the Balkans following the break-up of Yugoslavia, persuaded at least some Europeans that the EU needed to equip itself with a common intervention capability for crisis management when the Americans did not wish to be involved. France and the UK led the push for the development of a European Security and Defence Policy, which was established in 2000 and became the Common Security and Defence Policy in 2007. It provided the EU with new military capabilities and institutional resources in the defence realm. At the same time, NATO became involved in Afghanistan, leaving both organisations focused on similar themes of crisis response and peacekeeping.
NATO Primacy
From the 2010s onwards, the gradual end of the west’s expeditionary warfare and the return of the Russian threat brought changes. After Russia’s illegal annexation of Crimea in 2014 and the start of its war in Ukraine, NATO and the EU organised themselves to cooperate more closely on security issues, initially dealing with hybrid and cyber threats, as well as strengthening the defence industry and defence research, and cooperation on maritime security (the 2015-16 migration ‘crisis’ in Europe via the Mediterranean).[2]
In 2016 and 2017, 74 joint EU and NATO proposals for cooperative actions were identified in seven areas (hybrid threats, operational cooperation including maritime issues, cyber security, defence capabilities, industry and research and capacity building). At that time, the EU adopted its ‘Global Strategy’ with a section on defence, which included initiatives to strengthen the capabilities of the member states: Permanent Structured Cooperation and the European Defence Fund.
In 2018, alongside the NATO summit in Brussels, a second joint declaration was published, in which the two organisations agreed to take forward as priority proposals for cooperation in “military mobility, counter-terrorism, strengthening resilience to chemical, biological, radiological and nuclear-related risks [and] promoting the women’s peace and security agenda.”[3] The latest joint declaration was published in 2023. Its tone is somewhat different. Reflecting the consequences of Russia’s full-scale war in Ukraine, it includes elements from the strategic documents that NATO and the EU had adopted a year earlier (respectively the Strategic Concept and the Strategic Compass) and pledges that the two organisations would “strengthen our cooperation in existing areas, and expand and deepen our cooperation to address in particular the growing geostrategic competition, resilience issues, protection of critical infrastructures, emerging and disruptive technologies, space, the security implications of climate change, as well as foreign information manipulation and interference.”[4]
In a security environment now dominated by the military threat from Russia, it also underlines that “NATO remains the foundation of collective defence for its Allies and essential for Euro Atlantic security.” Thus, while NATO and the EU jointly acknowledged the Union’s growing role in security and defence, they also stressed NATO’s primacy as the cornerstone of the continent’s defence. This was demonstrated in practice in the same year when both Finland and Sweden applied for NATO membership.
Squaring agendas
Beyond the rhetoric, there has been concrete progress on the 74 proposals over the past years. This has been recorded in regular reports, the latest of which was published in June 2025 and mainly concerns the increase and diversification of interaction between the two organisations in all the agreed areas.[5]
Political dialogue is being strengthened. Meetings between the EU and NATO have increased significantly with a view to bolstering mutual understanding, whether through working meetings or more symbolic events such as the presence of the President of the Council and the EU High Representative at the Summit in Washington to mark the Alliance’s 75th anniversary. Since the signing of the 2016 Joint Declaration, more than 325 cross briefings have been held in various EU and NATO committees and working groups.
Cooperation on hybrid threats, resilience and strategic communication also continues at all levels with a view to ensuring that strategies are consistent and crisis responses predictable. For example, recent staff exchanges allowed for the integration of lessons learnt from the NATO baseline requirements for resilience initiative with the development of the EU’s Preparedness Union Strategy.[6] Exchanges of best practice and participation in cyber exercises have also taken place.
NATO and the EU jointly stressed NATO’s primacy as the cornerstone of the continent’s defence
At the operational level, there has been dialogue between military staffs, including cross briefings in the NATO and EU Military Committees, and cross participation in each organisation’s CHODs meetings. The implementation of the Parallel and Coordinated Exercises concept, meanwhile, has enabled both organisations to organise and participate in each other’s exercises, contributing to advancing both staffs’ understanding of their respective procedures, particularly in response to a hybrid scenario. The Commission also took part in NATO’s military exercise, Steadfast Duel 24, which tested the Alliance’s ability to respond to a range of threats, from traditional warfare to cyberattacks and hybrid threats.[7]
Joint efforts on maritime security are focused geographically on the Mediterranean and thematically on capacity building. NATO and the EU exchange information on their respective work in eight partner countries: Bosnia and Herzegovina, Georgia, Jordan, Iraq, Mauritania, Moldova, Tunisia, and Ukraine. As far as Ukraine is concerned, NATO has now assumed responsibility for the coordination of security assistance and training for Ukraine through the NATO Security Assistance and Training for Ukraine programme, while the EU is the main training provider for the Armed Forces of Ukraine through is Military Assistance Mission.
A Division of Labour?
The European security deck has been further reshuffled by Russia’s full-scale invasion of Ukraine. Today, there is a broad understanding—albeit not a formal one—that Europe’s primary task is to strengthen its military capabilities to deter, through NATO, the military threat posed by Russia, and that the EU can employ its various capability-building and defence instruments to underpin this process. The Commission has already proposed instruments which will allow the EU to mobilise its economic power and support the filling of NATO’s capability needs, in turn allowing the Alliance to properly implement its defence plans and strengthen deterrence. These instruments are intended to encourage investment by the EU member states and to mobilise the private sector. They include the European Defence Industrial Strategy and Programme, the Security Assistance for Europe instrument, the activation of the fiscal escape clause, the redirection of cohesion funds, and more flexible European Investment Bank rules. Other solutions, such as Eurobonds or increasing the defence allocation in the next EU budget, could also be found. Many of these will also have a direct impact on the ability of the NATO Allies to implement the new spending target they are expected to sign up to when they meet in the Hague.[8]
Information sharing is an obstacle to effective EU-NATO cooperation in capability development
In practice, this informal division of labour requires strong coherence between the various instruments of the two organisations concerning capability development: the EU’s Capability Development Plan, Headline Goal Process and Coordinated Annual Defence Review; and NATO’s Defence Planning Process and the Partnership for Peace Planning and Review Process. The EU White Paper for example, published in March, identifies as an EU objective the identification and coordination of capability requirements in line with NATO’s objectives.[9] The document also details the ReArm Europe plan, which aims to strengthen defence industrial production to support the needs of Europe’s armed forces.[10] The first Structured Dialogue on Defence Industry was launched this year to align NATO and EU objectives, promote interoperability, avoid duplication, and disperse Allied resources to support Ukraine and deter Russia. In the capacity sphere, NATO and the EU have also begun to discuss the strategic subjects of disruptive technologies (AI, quantum, biotech) and space.
Military mobility is a further priority area for work between the two institutions, as the large-scale movement of armed forces across Europe will require simplified border crossing procedures and investment in infrastructure, both of which partly fall under the EU’s remit. Already highlighted in 2016 as an area in which the two institutions could make progress together, it has become even more critical since Russia’s full-scale invasion of Ukraine.
Challenges
While the agendas of the two organisations have undoubtedly converged, there are still a number of challenges to their relationship. Above all, information sharing is still problematic due to the instrumentalisation of the conflict between Türkiye (not an EU member) and Cyprus (not a NATO member). This is clearly an obstacle to effective cooperation in capability development, where as much information as possible, including classified information, needs to be shared between the European Defence Agency and the NATO planners.
A second challenge is that European funding is usually conditional on a ‘European preference’—purchases of equipment or services must be collaborative and mainly produced in Europe. This is controversial within the EU, but even more so if it means that non-EU NATO Allies might be excluded. The US, which expects a large defence industrial bonus from increased defence spending in Europe, has already complained about this issue.[11] The potential that it could become an obstacle to more effective EU-NATO cooperation is evident.
Additionally, internal EU problems, including a lack of funding for military mobility, indicate that the Union needs to get its own house in order if it is to be able to mobilise the investment needed to acquire key capabilities.[12]
The Summit … and Beyond
The EU-NATO relationship will not be an issue on the formal, very truncated agenda of this year’s NATO summit. President of the European Council, António Costa, and President of the European Commission, Ursula von der Leyen, will, however, most likely join the informal leaders’ dinner on 24 June.
It remains to be seen what, if anything, President Trump’s very clear hostility towards the EU will mean for the further development of the EU-NATO relationship. It may be that it is simply too low-grade an issue to attract the administration’s attention. On the other hand, European preference could certainly become a flashpoint in the coming years, threatening to unravel several years of solid, if quiet progress.
Endnotes
[1] Andrius Sytas, “US to start European troop withdrawal discussions later this year, US NATO ambassador says,” Reuters, 16 May 2025; Guy Chazan, “Why does Maga world hate Europe?” Financial Times, 5 June 2025.
[2] European Union, European Commission, “Joint declaration by the President of the European Council, the President of the European Commission, and the Secretary General of the North Atlantic Treaty Organization,” 8 July 2016 .
[3] European Union, European Commission, “Joint Declaration on EU-NATO cooperation by the President of the European Council, the President of the European Commission, and the Secretary General of the North Atlantic Treaty Organization,” 10 July 2018.
[4] NATO, “Joint Declaration on EU-NATO cooperation by the President of the European Council, the President of the European Commission, and the Secretary General of the North Atlantic Treaty Organization,” 9 January 2023.
[5] European Union, Council of the EU, “EU-NATO : 10th progress report reaffirms commitment to advancing cooperation amid instability and security challenges”, 10 June 2025.
[6] European Union, European Commission, “EU Preparedness Union Strategy to prevent and react to emerging threats and crises,” 26 March 2025.
[7] NATO Allied Command Transformation, “NATO’s Steadfast Duel 2024: A Test of Alliance Readiness and ACT Experimentation,” 6 November 2024.
[8] Felix Gasper, ” The Central Issue. Defence Spending,” ICDS, June 2025.
[9] Marianne Paire, “The White Paper for European Defence Readiness 2030,” ICDS, 7 April 2025.
[10] Marianne Paire, “Strengthening the Industry,” ICDS, 18 March 2025.
[11] Gram Slattery, John Irish and Daphne Psaledakis, “US officials object to European push to buy weapons locally,” Reuters, 2 April 2025.
[12] Mihai Chihaia, “Military Mobility a Critical Enabler,” ICDS, 27 May 2025.
Disclaimer: The views and opinions contained in this paper are solely of its author(s) and do not necessarily represent the official position of the International Centre for Defence and Security or any other organisation.
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