Channelling security: A new era for EU-UK defence cooperation

Since Brexit, defence has barely registered on the EU-UK cooperation agenda. Instead, NATO or bilateral frameworks have served as the default—and often preferred—framework for defence collaboration across the Channel, reflecting a lack of political appetite for a bilateral EU-UK-focused approach.

This changed within days of Donald Trump’s return to the US presidency. It suddenly became abundantly clear to London and Brussels that America was no longer willing to play its traditional role as Europe’s security provider. Britain and the EU are now keen to identify the best institutional approach and the priority areas for defence cooperation. The EU-UK defence and security pact, which will likely be signed on May 19th, is an important first step in a broader, multifaceted approach to enhancing defence cooperation.

Getting the format right

Until now and besides the NATO framework, cross-channel defence cooperation has largely taken place through ad hoc bilateral or mini-lateral arrangements, such as the 2010 Lancaster House Franco-British Treaty and the 2024 German-British Trinity House agreements. Ideological differences, and more recently the scars of Brexit, influenced this preference for flexible coalitions over institutional EU-UK frameworks. Formats like the Joint Expeditionary Force and the Weimar+ or E5 (France, Germany, Italy, Poland and the UK) group, along with Franco-British efforts to support Ukraine, further illustrate this trend.

This preference for “coalitions of the willing” and other lighter forms of ad hoc cooperation can be useful stepping stones. For example, any nuclear conversations among Europeans will not take place under an EU umbrella. Bilateral formats will continue to matter as the first deliverables of the Trinity House agreement and the likely substantive Franco-British summit in July 2025 demonstrate. And some European operational cooperation will continue to be developed in these bilateral or mini-lateral formats when an EU framework does not really exist. This will not be to the point of resurrecting the 1948 Western European Union but could include formalising a like-minded European defence format.

But the current security situation requires European countries to work towards a stronger, more formal format than this. The EU-UK pact is a good opportunity to set the tone for such a relationship, but it will require steady and good faith efforts on both sides—especially considering the starting point.

The EU-UK pact offers a good opportunity to set the tone for a stronger and more formal relationship, but it will require steady and good faith efforts on both sides

The UK, for example, does not have an administrative arrangement with the European Defence Agency, whereas America, Norway, Switzerland, Ukraine and Serbia all do. Such arrangements are formally prerequisites for real cooperation with the agency. To bridge this gap, London will need to move away from its approach of defending third-party access to EU projects and instead seek ways to more closely participate in line with its own national interests. For its part, the EU needs to acknowledge that the UK (like Norway) is an important part of the European Defence and Technological Industrial Base (EDTIB) and should therefore be a distinct partner from other third parties around the globe.

This state of play should only encourage work to begin on the terms and conditions for a new chapter in the EU-UK defence relationship. As this work begins, there are six guiding principles policymakers on both sides of the Channel should consider.

Principles for cooperation

1. Delivering security for Ukraine

The immediate priority should be to jointly address the future of Ukraine. The British government, the EU and (most of) its member states are well aligned on the need to achieve a settlement that would not undermine the long-term sovereignty of Ukraine and put European security at risk by emboldening Russia.

This requires close alignment on two sets of issues. First, providing long-term military assistance to Ukraine so it can defend itself from continued or renewed Russian aggression. Europeans (EU and non-EU) already account for roughly half of the assistance provided. A joint and shared effort to sustain a solid level of support, especially should US assistance be severely diminished or discontinued, is essential for the long-term future of Ukraine. It also serves Europe’s security interests. London, Brussels and other European capitals need to develop a plan to that effect including through the support of Ukrainian domestic production.

Second, the issue of security guarantees is still on the table under a Franco-British lead coalition of the willing. Whatever form they ultimately take and whatever degree of US backstop exists, it will be a test for Europeans’ ability to work together without US leadership and deliver a critically needed element of a stable post-conflict settlement, and a test of the willingness of London to develop and use new ad hoc formats.

2. Addressing the roadblocks to a closer relationship

For any pact to succeed, London and Brussels need to tackle the structural barriers to cooperation. Signing an administrative arrangement with the European Defence Agency would facilitate full British participation in Permanent Structured Cooperation projects including some in which other non-EU NATO allies participate (such as military mobility). The EU should also work towards associating Britain in the developing toolbox of EU financial instruments that support defence investment based on mutually agreed contributions and benefits. The experience of bringing the UK back into long-term EU research projects—most notably, Horizon Europe—could serve as a useful precedent.

The EU-UK pact needs to offer the political impetus and the roadmap to achieve these immediate objectives within months, rather than representing the start of a drawn-out bureaucratic process.

3. Defining the terms of the EDTIB

Strong cross channel industrial cooperation that involves a wide range of defence companies, including some pan-European companies such as MBDA, shows that the UK is very much part of the EDTIB, despite the strong transatlantic ties of British industry. While there is a transatlantic defence market, the EDTIB is unique and has been built through decades of European cooperation (albeit including some historic failures).

The British defence industry offers a lot to Europe and would immensely benefit from further developing European partnerships as the European market is expanding fast. But first, this will require full recognition from both sides. In recent years a number of major projects seemed to be going in the opposite direction. Britain, for instance, was seeking to primarily develop industrial and technological partnerships beyond Europe (AUKUS being a case in point); while the EU moved towards tools that favoured member states. This complicated UK participation in major European projects. Embarking on a deliberate effort to enable defence cooperation will require a strong and sustained political push on both sides of the debate.

4. Relaunching and revisiting the 2000 Letter of Intent Framework Agreement

One oft-forgotten framework that could benefit from a dusting off is the 2000 Letter of Intent Framework Agreement Treaty signed in Farnborough by the defence ministers of France, Germany, Italy, Spain, Sweden and the UK. Bringing together the six biggest European defence industry players, it aimed to create the political and legal framework necessary to facilitate industrial restructuring in order to promote a more competitive and robust EDTIB in the global defence market through tackling six areas: security of supply, transfer and export procedures, security of information, research, treatment of technical information, and harmonisation of military requirements. In a post-Brexit environment, it could be adapted within the new role of EU institutions such as the European Defence Agency. Its scope and framework are nevertheless fit for present-day challenges.

5. Promoting a fundamentally revised NATO-EU relationship

This may at first sight appear to be a bureaucratic task. But it is deeply intertwined in the EU-UK relationship. As a staunch defender of the transatlantic alliance and an influential ally within NATO, the UK has consistently been at the forefront of defending NATO’s pre-eminence in defence. This has been particularly evident since Brexit, with the UK criticising the EU for developing autonomous capacity. In its passionate defence of NATO, the UK has often looked like more of a spoiler in the debate with the EU rather than a promoter of a balanced relationship. To become an advocate of an ambitious European partnership, London should leave this posture behind and promote a renewed and expanded NATO-EU relationship.

6. Addressing the coexistence of two “special relationships”

This is possibly the most complex challenge for London. The special relationship with Washington has developed over eight decades and created unique ties in sensitive domains such as intelligence and nuclear deterrence. There are excellent reasons not to renounce this relationship as long as Washington is willing to sustain it.

It should not, however, cancel out the possibility of a new “special” relationship with the EU, which could possibly focus on different areas such as industrial and operational cooperation. From the EU perspective, most member states—although for different reasons and priorities—could endorse such an effort to build an EU-UK special connection.

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Europe needs to act as one, and having the UK as part of that one reflects a simple recognition that non-EU states are necessary to defend Europe with less America. The most recent developments have already demonstrated a remarkable pan-European strategic alignment. A further deterioration of the European security environment cannot be ruled out. London and Brussels owe it to themselves and each other to build on the current momentum to transform their defence relationship immediately. This might require some difficult trade-offs and letting old habits die, but for Europe, the result will be indispensable.