The partnership between NATO and the European Union has moved well beyond the declaratory stage. With 23 countries belonging to both organisations, a shared border on Europe's eastern flank, and a common adversary in Russia, the two institutions have spent the past decade converting political unity into operational interlock. The most recent joint declaration, signed on 10 January 2023 by the NATO Secretary General, the President of the European Council and the President of the European Commission, added emerging technologies, space, climate security and foreign information manipulation to a cooperation agenda that already covered hybrid threats, cyber defence, military mobility and crisis management exercises.

From Berlin Plus to three joint declarations

The legal backbone of the relationship remains the 2003 Berlin Plus arrangements, which give the EU access to NATO's collective assets and planning capabilities for EU-led military operations. But the partnership has expanded considerably since the first joint declaration in 2016, when NATO foreign ministers endorsed 42 concrete measures across seven areas. A second declaration in 2017 added 32 more, introducing military mobility, counter-terrorism information sharing and women, peace and security. The 2023 declaration, signed weeks before the first anniversary of Russia's full-scale invasion of Ukraine, reflected a security environment that had fundamentally shifted since 2017.

The 2023 text committed both organisations to a Task Force on resilience and critical infrastructure protection. That Task Force, created by the NATO Secretary General and the President of the European Commission, reported in June 2023 with recommendations spanning energy, transport, digital infrastructure and space. Its findings now feed into staff-to-staff work on alternate transport routes, joint security research and more systematic information exchange.

Military mobility becomes a test case for interoperability

Few areas illustrate the practical challenges of NATO-EU cooperation as clearly as military mobility. The Structured Dialogue on Military Mobility, established in 2018, brings together military planners, transport ministries, customs authorities and infrastructure managers from both organisations. Its remit covers everything from weight limits on bridges to the cross-border paperwork for dangerous goods. NATO contributes to the development and updating of the EU's military requirements for mobility within and beyond EU territory, with particular attention to critical transport infrastructure.

The logic is straightforward: 23 nations have a single set of forces and finite budgets. If NATO's Defence Planning Process and the EU's Capability Development Plan pull in different directions, both suffer. Cross-participation in meetings and staff-to-staff contacts are meant to align the output of the EU's Headline Goal Process and Coordinated Annual Review on Defence with NATO's Planning and Review Process. Progress is measurable but uneven; officials on both sides acknowledge that national procurement cycles and industrial preferences still create friction.

Hybrid threats and cyber defence: the Helsinki-Tallinn axis

Countering hybrid threats has become a daily operational reality. The European Centre of Excellence for Countering Hybrid Threats in Helsinki functions as a permanent forum for NATO-EU exchanges, while the NATO Cooperative Cyber Defence Centre of Excellence in Tallinn hosts exercises in which both organisations participate. A technical arrangement between the NATO Cyber Security Centre and CERT-EU, the computer emergency response team for EU institutions, provides a framework for incident information sharing and best-practice exchange.

Staff-to-staff consultations on cyber crisis management have intensified, partly to avoid duplication and partly because the threat landscape, state-sponsored intrusions, ransomware against critical infrastructure, disinformation campaigns, does not respect institutional boundaries. The two organisations also coordinate capacity-building for partners in the Western Balkans and the eastern neighbourhood, where Russian hybrid activity remains persistent.

Crisis management exercises move from ad hoc to systematic

The Plan for Implementation of Parallel and Coordinated Exercises (PACE) has turned what were once occasional tabletop drills into a standing cycle. Under PACE22, NATO staff participated in the planning and conduct of the EU's Integrated Resolve Exercise. Under PACE23, European Commission, Council and European External Action Service staff took part in NATO's crisis management exercise. The PACE cycle for 2024-2025 was agreed in February 2024, embedding reciprocal participation as a routine rather than an exception.

These exercises matter because they test the Berlin Plus machinery in near-real conditions: can an EU operation headquarters plug into NATO's command structure seamlessly? Can shared situational awareness survive competing classification rules? The answers shape the credibility of the partnership more than any summit communiqué.

The non-EU ally question

A structural asymmetry runs through the relationship. Twenty-three NATO allies are EU members; nine are not. Norway, Turkey, the United Kingdom, Canada, the United States, Iceland, Albania, Montenegro and North Macedonia have no vote in EU defence decisions but contribute forces, capabilities and intelligence that EU operations rely on. The 2003 framework and subsequent declarations acknowledge this, but practical involvement remains case-by-case. The Aegean activity of 2016, where NATO ships supported Greece, Turkey and Frontex in the migration crisis, showed how non-EU allies (Turkey, the US, Canada) can be integrated into an EU-relevant mission, but only because Turkey, a NATO ally and EU candidate, was a direct party.

The Western Balkans remain a laboratory for this dynamic. The 2003 Concerted Approach for the Western Balkans, jointly drafted by NATO and the EU, still guides cooperation in a region where several countries are NATO members but not EU members, or vice versa. Bosnia and Herzegovina, a NATO partner with EU candidate status, exemplifies the overlapping but distinct conditionality tracks the two organisations manage.

Resilience and critical infrastructure: the new frontier

Modern societies depend on interconnected critical infrastructure, power grids, undersea cables, satellite constellations, transport hubs. That interdependence creates efficiency but also cascading vulnerability. The 2023 Task Force's final assessment highlighted energy, transport, digital infrastructure and space as priority domains where NATO's military requirements and the EU's regulatory tools must align. Recommendations include joint mapping of alternate transport routes for civilian and military mobility, coordinated border-crossing legislation for dangerous goods, and closer ties in security research.

Implementation is now the test. The EU's Critical Entities Resilience Directive and NATO's resilience guidelines cover overlapping ground; the challenge is to avoid parallel reporting burdens for operators while closing gaps. The Task Force's call for more systematic information exchange between NATO's intelligence fusion mechanisms and the EU's hybrid threat analysis units remains a work in progress.

Organisations

North Atlantic Treaty Organization · European Union · European Commission · European Council · European External Action Service · European Defence Agency