EU-UK summit: implications for European security and beyond
A security and defence pact is critical for European security - and can set the scene for cooperation on the global level.
The EU-UK summit will take place on 19 May. One of the key items on the agenda is the signing of a security and defence pact between Brussels and London, as these topics were systematically excluded from the Trade and Cooperation Agreement (TCA), which outlined cooperation between the EU and the UK in the aftermath of Brexit. With the start of Russia’s full-scale invasion of Ukraine, increasing uncertainty about the United States strategic priorities and future involvement in European security, and shifts in the global order, London and Brussels are now moving closer together again. A new chapter in security and defence cooperation between the UK and the EU will not only have implications for European security and defence, but also provides more general insights into cooperation in times of heightened geopolitical pressure.
Background
Since its election in summer 2024, the British government under Keir Starmer has prioritised a “reset” with the EU, especially in security and defence policy. While the previous UK government was at the forefront among Europeans to support Ukraine and closely coordinated with its European partners, including the EU, the relationship remains informal. Security and defence policy is not covered by the TCA, and until now, cooperation between the UK and the EU in this field only occurred on an ad hoc basis. While London applied to join the EU’s military mobility project under the Permanent Structured Cooperation (PESCO) in 2022, which was generally considered an important milestone for enhancing the relationship, it is still formally blocked from joining the project because of a Spanish veto due to disputes over Gibraltar.
Before the start of Russia’s full-scale invasion of Ukraine, this ad hoc approach and muddling through might not have contributed to better relations between the EU and the UK. Especially the 2021 Integrated Review, which described the UK’s aspiration of becoming Global Britain, raised questions among European partners to what extent London was going to be a partner in the future because it strongly emphasised the strategic importance of regions outside Europe for the UK — some commentators even referred to a “Europe-shaped hole” in the document. Following the start of the full-scale invasion, the 2023 refresh of the document clearly readjusted the UK’s focus back to security and defence on the continent. Nevertheless, this adjustment was never followed by an institutionalisation or intense engagement with the EU, not least because there was little political interest (and no elections to win) for a conservative government to do so. In security and defence policy, the UK could also continue to rely on engagement and defence diplomatic ties with European partners through NATO, which has traditionally been the backbone of the UK’s approach to security cooperation on the continent.
The political momentum for a reset of the relationship arose with the elections in the UK in summer 2024, as re-engaging with European partners had already figured in the foreign policy agenda of the Labour party ahead of the elections. The urgency to enhance cooperation was however catalysed by the election of Donald Trump as US President and his unpredictable approach to NATO and European security more generally. As European states become increasingly aware that Europe’s security will be a predominantly, and perhaps exclusively, European responsibility, they must find more effective ways to cooperate on the challenges ahead, be it rearmament, support for Ukraine, or a strategic vision for the continent — hence the willingness in London and Brussels to engage in negotiations on a security and defence pact.
In the past, Starmer has participated in summits of the EU leaders, which was a strong political signal towards Brussels that the UK was committed to forging closer ties with the Union; nevertheless, the UK’s status as a partner is, formally speaking, not different from any other third country. The considerable shifts in the European security order, and the risk of more to come, might change this.
Why it matters
Closer cooperation between the EU and the UK is particularly important in light of Russia’s war against Ukraine and the changing US posture on Europe.
On Ukraine, the UK had previously actively engaged with its European partners through NATO and the G7, for example on sanctions. In the future, the EU and the UK must prepare for being solely responsible for supporting Kyiv militarily, as it seems extremely unlikely for the United States to pass another military aid package for Ukraine. Furthermore, cooperation in NATO to further support Ukraine will be increasingly complicated due to the risk of US veto on key decisions, such as Ukraine’s accession to NATO. In parallel, the EU is likely to play an increasingly important role in this field: not only does the new White Paper on EU defence explicitly include the “porcupine strategy” for Ukraine — meaning massive military support for Ukraine to defend itself —, but the bloc’s engagement with Ukraine in the framework of the enlargement process will also lead to major reforms and more alignment between the EU and Ukraine on key issues. Accordingly, tapping into these structures for support through more formalised cooperation with the EU can facilitate London to uphold its commitments for Ukraine.
On the future of the European security order, engaging with the EU appears increasingly salient for the UK as the United States openly questions its commitment to European security and the alliance. Many questions remain, but it is almost certain to say that the United States will withdraw from European security — the question is to what extent and how fast this is going to happen. As Europeans will have to step up their commitments to European security in terms of capabilities and strategy, the EU can significantly contribute to financing and coordinating these efforts. There is little appetite among EU member states to upgrade the EU to a military superpower and to replace NATO; even if there are questions related to the US commitment to the alliance, NATO also remains a military alliance among Europeans states, and the structures in place constitute a strong basis to strengthen cooperation among Europeans and construct a truly European base for NATO. However, the alliance lacks the financing instruments which will be necessary to build a European defence industrial base to materially equip Europeans for the challenges ahead. Furthermore, the EU has considerably stepped up its efforts and instruments against hybrid threats, including disinformation or election interference; none of these challenges are bound geographically, but rather result from states’ choices and positioning in the global order — and the UK and the EU find themselves on the same sides in this regard. If the UK does not want to be sidelined in these efforts, cooperation with the EU is inevitable.
Ukraine and the broader question of the European security order illustrate that the UK cannot escape geography; as most of its neighbours are members of the EU and increasingly tap into its instruments on security and defence, the UK risks missing out if cooperation remains on an ad hoc basis. Even beyond these two pressing challenges, a formalised pact for security and defence cooperation can facilitate joint action of the EU and the UK; examples could include crisis management or missions to uphold the freedom of navigation.
What’s next?
The expectations around the summit are mixed. As the messaging about the content of the security and defence pact remains relatively limited, some have described it as a case where Europeans “underpromise and overdeliver”. At the same time, the political climate between the UK and the EU still remains tense due to other files that have not been resolved since Brexit — think about fisheries or the unresolved questions around youth mobility. Questions about access to the single market, where London is often accused of cherry-picking, complicate the negotiations. Politics also weighs heavily on both sides: with the risk of Reform gaining strength in the next elections in the UK in 2029, London’s European partners might be hesitant to go all in. The level of ambition for the summit is hence deliberately low — but more could be achieved if both sides change their approach: “ The EU will need to be more forward-looking and flexible; the UK will have to be more ambitious and prove itself trustworthy.”, write CER experts.
The key question for the EU and the UK is, however, what happens after the signature of the pact. Unless underpinned by clear political will to translate bloomy declarations into actual action, the pact itself will not have a palpable effect.
Most importantly, the conclusion of an EU-UK security pact will not resolve the key challenge for Europeans, which is a genuinely European vision for the future of European security. The Trump administration is unlikely to actively engage in strategising on the future of the European security order — and if it does, Europeans need to brace for a situation where the vision of Washington might considerably diverge from their priorities. Given the strong role of national governments in shaping these reflections, mostly through intergovernmental negotiations, a security pact between the EU and the UK will most likely not replace these processes, but aligning the instruments and mechanisms can benefit this process through underpinning it materially.
As British Prime Minister Starmer has attempted to position the UK as a “bridge” between Europe and the United States when tensions peaked, some consider it as a balancing act for the UK to maintain this approach after the conclusion of a security pact with the EU. However, these concerns do not appear highly relevant: on European security and defence, the Trump administration barely interacts with the EU as a bloc but rather with individual heads of state, as reflected in his exchanges with French President Macron or British Prime Minister Starmer rather than EU Commission President von der Leyen.
Coming together under a geopolitical stress test
The EU-UK summit is held at a time where the situation in Ukraine and the future of the European security order are the central issues of preoccupation, and it clearly demonstrates that the rapprochement is the result of a geopolitical stress test. However, its implications can go far beyond the most pressing issues for European security. Most importantly, a security and defence pact can contribute to enhancing trust and processes of cooperation between the EU institutions and the UK as well as individual member states and the UK; it thereby recreates a certain level of socialisation and ties of cooperation that have suffered from the Brexit years.
Especially in light of the significant shifts in the global order and new emerging security challenges, be it through new realms of international security, such as space or cyber, or theatres outside Europe, the pact can set the tone for further cooperation between the EU and the UK. Both sides are likely to be similarly effected by international security challenges in the future: in case of a major conflict in the Indo-Pacific or attacks on shipping lanes in the Red Sea, both the EU and the UK would be directly affected by the ramifications for global trade. In case of a resurgence of international terrorism, levels of alert would increase in EU member states as well as the UK. And if increasing competition or even conflict between the United States and China forced European states to choose sides, it seems unlikely for the UK to be spared simply because it is not an EU member state. Especially in the context of US-China competition and increasing cooperation between middle powers, enhancing cooperation between the EU and the UK and prioritising foreign policy cooperation can also constitute a first step in creating broader multilateral coalitions on common goods.
A security and defence pact might find its origins in the current security challenges in Europe, but it can be a stepping stone for further cooperation in the future on broader security challenges. One can only hope that Brussels and London seize this momentum not only for a summit declaration, but take it as a starting point for more systematic engagement. Most importantly, a positive outcome of the summit would imply a positive impetus for the relationships of the UK with its European partners, creating a basis for higher trust and signalling political willingness to overcome challenges. Such an outcome could hence have positive spillover effects on cooperation in bilateral and minilateral formats of cooperation in European defence, which have often played a key role in shaping European initiatives in the field — and are, realistically, more likely to do so than the EU.