The European Union, the United Kingdom and defence: Towards a strategic partnership

The need for a relationship between the United Kingdom (UK) and the European Union (EU) in the field of defence is evolving as the European security environment changes, the EU acquires competences in this area, and the British government takes a favourable view of the benefits of closer ties with the EU.

For their part, the European Union and its Member States are reasonably open to the idea of renewed cooperation with the United Kingdom, which offers clear military and industrial capabilities.

Indeed, the war in Ukraine has provided the framework for successful cooperation between the two parties.

Against this backdrop, on 19 May 2025, the EU and the UK signed a Security and Defence Partnership designed to revitalise their relationship by promoting greater cooperation in the areas of strategic dialogue, the Common Security and Defence Policy (CSDP) and the defence industry. From the UK’s perspective, this forms part of the ‘reset’ of relations between the UK and the EU called for by then Prime Minister Keir Starmer shortly after he came to power in the summer of 2024.

However, nearly eighteen months after the Partnership was signed, the relationship between the two sides has not progressed as expected and does not reflect a strategic-level partnership, which does not appear to be a priority for either the EU or the UK.

Dialogue at various levels has been launched and the UK’s participation in the Permanent Structured Cooperation (PESCO) project on Military Mobility has been revived but the lack of progress in cooperation on CSDP or with the European Defence Agency, and of course the failure of negotiations on the Security Action for Europe (SAFE) programme, are more indicative of a struggling reset than of a mutually beneficial revival of cooperation.

The reasons for the deadlocks are known: on the one hand, a United Kingdom that is ultimately primarily interested in European projects linked to the defence industry rather than in the CSDP, and which appears to want to take rather than give; and on the other, an EU (and its Member States) that is open to closer ties but keen to adhere to its strict rules on partnership with third countries, and not to open the door to a ‘Europe à la carte’.

Against this backdrop, cooperation between the UK and the EU must remain a priority for two players who need one another at a time of Russian aggressiveness and American ‘abandonment’.

They must therefore move towards a renewed sense of shared purpose, the establishment of more institutionalised channels of cooperation and a more robust operational partnership – efforts that are essential to their respective growth and credibility in the defence domain, including in the industrial sphere.

Beyond this, the question arises as to whether the Security and Defence Partnership is adequately suited to the current security challenges. Both parties have good reasons to be cautious in their defence relations, and certain European states also have substantial bilateral relations with the United Kingdom.

However, the current security environment is unprecedented, and if the prospect of a direct confrontation with Russia is credible, then should one not, in turn, devise a defence partnership between the EU and the UK that is commensurate with this challenge?

In the medium term, it is the idea of a genuine, bespoke strategic partnership between the EU and the UK that deserves to be discussed and put in place. A truly strategic partnership in that it would enable a response to the urgent threat posed both by Mr Putin and Mr Trump, and address broader issues than those covered by the Security and Defence Partnership.

Establishing this partnership would require the EU to be more open and the UK to be more determined to push for it. But above all, it would require both parties to recognise that, alongside their actions at national, bilateral or NATO level, their partnership is also an essential element in responding to contemporary strategic challenges.