The need for a UK-EU defense pact

British Prime Minister Keir Starmer met with European Commission President Ursula von der Leyen in London late last month to discuss the future of UK-EU relations. The main purpose of the meeting was to prepare for a larger summit between London and Brussels this month that will focus on formalizing cooperation on security and defense.

Since the historic 2016 referendum that led to the UK formally leaving the EU four years later, there has been an ongoing political debate about what the future relationship between the UK and the EU should look like. Starmer last year campaigned on aligning the UK more closely with the EU, but he has so far acted cautiously, aware that many Labour voters supported Brexit. At the same time, he has sought to distinguish himself from his Conservative predecessors, who were widely seen as presiding over chaotic and unproductive negotiations with Brussels.

In the Labour Party’s 2024 election manifesto, a clear commitment was made to establish a new security pact with the EU. Both sides hope this agreement will be finalized later this month.

Both London and Brussels want a security agreement, but for different reasons. For Starmer, it is an opportunity to demonstrate that he represents a clean break from the past and can reset the UK’s relationship with Europe. That the first major agreement focuses on defense and security is no coincidence — this is a policy area where the UK has significant strengths and can bring a great deal to the table. The UK has one of the largest defense budgets in Europe, a global military presence and extensive intelligence and cybersecurity capabilities.

Security is a policy area where the UK has significant strengths and can bring a great deal to the table

Luke Coffey

From the EU’s perspective, a deal is also urgent. The bloc recently announced a €150 billion ($169 billion) initiative to invest in the European defense industry. But without a formal agreement with the UK, British defense companies will be largely excluded from participating. Cooperation with the UK would enhance Europe’s capabilities and bolster transatlantic security.

Despite lingering Brexit-related bitterness in some corners of Brussels, the geopolitical reality is that the EU can never be fully secure without close cooperation with Britain. The UK has been a major European power for centuries and this will remain the case regardless of its EU membership status. EU officials hope that success in forging a defense agreement this month could create momentum for deeper cooperation in other areas — especially fishing.

Few issues are as contentious in the EU as fishing rights. Determining which country can fish where, and how much, remains deeply political. In fact, it is one of the key reasons countries like Norway have opted to stay out of the EU. Currently, the UK and EU are in a transitional phase until June 2026, during which EU coastal states may still fish in British waters. Some EU officials have hinted off the record that progress on defense cooperation may hinge on the UK offering assurances about future fishing access. At the very least, Brussels hopes that accommodating the UK on defense — an issue important to London — will generate reciprocity on fishing, which is an issue important to the EU.

Beyond bilateral tensions, global events are pushing the UK and EU toward greater defense cooperation. First is Russia’s full-scale invasion of Ukraine in 2022, which served as a wake-up call across the continent. It reminded policymakers that institutional affiliations are secondary to the more urgent need for security and deterrence. Debates about the EU’s role in defense compared to NATO, which previously consumed so much political bandwidth, now seem almost irrelevant in the face of such a clear and present danger. Without Russia’s aggression, it is likely there would be far less emphasis today on the need for renewed UK-EU security arrangements.

Second is the return of Donald Trump to the White House. During his first term, Trump criticized European allies for underinvesting in their own defense — criticism that many Europeans acknowledged as fair. In response, European states have begun increasing military spending. However, Trump’s second term has brought an even sharper tone, with Washington openly declaring a trade war on the EU and signaling a pivot to East Asia in its defense planning. This has further galvanized European leaders to look inward and strengthen their collective defense capabilities.

The geopolitical reality is that the EU can never be fully secure without close cooperation with Britain

Luke Coffey

Still, there is a risk that closer UK-EU cooperation could come at the expense of the UK’s special relationship with the US or NATO’s primacy in European security. That risk must be managed carefully. The UK has historically been one of NATO’s strongest supporters and has often acted in Brussels to block EU defense initiatives perceived as duplicative of NATO. Any new pact with the EU must preserve NATO’s central role in European defense, while allowing for collaboration in areas where the EU can play a complementary role — such as cyber threats, hybrid warfare, energy security, infrastructure protection and combating disinformation.

While it was still in the EU, the UK pursued bilateral defense agreements with European countries — most notably the 2010 Lancaster House Treaties with France. These agreements were intended to demonstrate that Britain could take a leadership role in European defense outside EU structures. Now, having left the bloc, the UK is naturally seeking to complement these bilateral relationships with a formal agreement with Brussels — without undermining NATO’s essential role.

There will no doubt be skepticism from some Brexit supporters and euroskeptic commentators in the UK about any formal defense cooperation with the EU. But as long as it is done in a way that prioritizes NATO and makes the continent of Europe safer, it could represent a win-win for all sides. The EU gets a stronger, more capable partner on defense and the UK reasserts its leadership role in European security — while ensuring that its alliances with both Washington and Brussels are fit for today’s geopolitical challenges.

• Luke Coffey is a senior fellow at the Hudson Institute. X: @LukeDCoffey