The role of the UK in a new European security architecture


The United Kingdom has developed its contribution to European security in the context of its withdrawal from the EU. However, a more formal relationship between the two in the areas of foreign, security and defence policy remains to be desired.

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The British Prime Minister Rishi Sunak at the annual Joint Expeditionary Force Summit in Riga, Latvia.

Russia’s war on Ukraine has overturned the European security order. The challenge for the leaders of Europe’s nation states (and its key institutions) is to build a new European security architecture robust enough to manage Russia and to meet wider future threats to peace and stability. Sturdy arrangements are needed to counter Russia’s appetite for war and to establish deterrence against future Russian aggression.

What is the role for the UK in countering the challenges to Europe’s security and how does this inform its preferences for the European security architecture? There are at least three dimensions: first, seeking a vanguard role in assisting Ukraine’s capacity to provide for its defence and security; second, acting as a catalyst for new security and defence relationships in Europe; third positioning itself as a thought leader on future arrangements for European security.

Ukraine: early adopter

The UK has had a decade-long security and defence relationship with Ukraine and that has focused on enhancing the country’s military capabilities. With Operation Orbital, launched in 2015, following in Russia’s occupation of Crimea, the UK focused on training and upskilling Ukraine’s armed forces to NATO standards. Further, Britain was an ‘early adopter’ in supporting Ukraine’s capacity for countering Russia’s armed forces with the transfer of anti-tank weaponry in the weeks leading up to Russia’s invasion in February 2022. The UK’s own experience of the capacity for reckless actions of the Russian state had been experienced directly with the use of nerve agents on British soil with the Novichock poisonings in Salisbury in March 2018. This had provided further reinforcement of the impetus needed to counter the actions of the Putin-led regime that was willing to engage in norm-breaking behaviour. Consequently, the UK was one of the strongest voices in Europe warning against Russia’s plans for what was subsequently to result in the February 2022 large-scale military invasion of Ukraine. And subsequently has sought to push the boundaries for the level of support provided to Ukraine in terms of the type of weapons sent in advance of other states (for example, Next Generation Light Anti-Tank Weapons, Challenger 2 Main Battle Tanks, Storm Shadow cruise missiles), the value of direct military support, and the extent of out-of-country training for the Ukrainian armed forces (via the INTERFLEX land forces training programme; and the Air Force Capability Coalition training F16 pilots).  

There has been no alteration in UK policy on Ukraine in spite of the turnover of British Prime Ministers since 2022. The current Prime Minister Mr Sunak has maintained the same level of diplomatic and military support to Ukraine as his predecessors including the announcement of a further £2.5bn of military aid in mid-January (which is also to include the largest delivery of drones to Ukraine from any country). The UK is also the first member of the G7 to deliver on the Joint Declaration made by its members (and subsequently joined by 24 other states) in July 2023 to collectively provide bilateral security commitments to Ukraine. A Security Co-operation Agreement was signed by the UK on 12th January 2024 for a 10-year duration and with the purpose of providing Ukraine with security commitments that are intended to act as arrangements to assist Ukraine in providing for its security until it is integrated into Euro-Atlantic security institutions.

Brexit catalyst for new security and defence relationships

The UK’s actions in support of Ukraine since February 2022 have been a reminder of its role in European security and which was previously overshadowed by the domestic political turmoil of the Brexit process.

For the UK itself, the domestic preoccupation of Brexit impacted on its capacity to clearly articulate its intended future role in Europe outside the EU. ‘Global Britain’ was adopted as the organising label for a new foreign policy by the UK Government shortly after the June 2016 Brexit referendum. However, full articulation of its meaning for the country’s international role only came with the process that resulted in the publication in March 2021 of Global Britain in a Competitive Age: The Integrated Review of Security, Defence, Development and Foreign Policy (IR). The IR re-capitulated the idea that Britain was a Euro-Atlantic power and that in terms of security and defence it remained overwhelmingly focused on Europe, albeit with an Indo-Pacific ‘tilt’.

Fast forward from 2020 to 2023 and the ‘refresh’ of the IR summarised how Britain had fleshed out where it saw its role in Europe with reinvigorated bilateral relationships (including with France), a greater impetus to a series of minilateral partnerships (most notably via the 10 nation Joint Expeditionary Force lead by the UK) and with significant political energy devoted towards NATO, viewed as where the vast bulk of the UK’s security and defence efforts were to be focused in Europe. The UK has also been strongly of the view that European and Indo-Pacific security were entwined and most clearly articulated in its analysis of China as ‘an epoch defining challenge to the type of international order we want to see’ in the refreshed IR.

As the UK has moved to firm-up its own understanding of its place in Europe and to re-engineer relationships with a number of European states it has put the relationship with the EU on a stable basis following agreement on the EU-UK Trade and Cooperation Agreement (TCA) in 2020 and the Windsor Framework in February 2023.

Until February 2022, the UK had remained disconnected from the EU’s CFSP and CSDP. In exiting the EU, the Johnson-led Government had not sought negotiations with the EU for a formal agreement in this area to cover cooperation post-Brexit. Consequently, the TCA has minimal provisions covering EU-UK international cooperation. Since Russia’s actions in February 2022 the EU and UK, even in the absence of formal structures for foreign, security and defence cooperation, have, however, sought to coordinate their support to Ukraine (most notably on sanctions but also on their respective military training operations) and been brought together within their shared membership of the G7, which has been the key forum for defining the objectives and collective actions in response to Putin’s war.

Now outside the EU the UK has obviously not been a party to the EU’s policy response to Ukraine. The new departures for the EU in providing military support for Ukraine, the financial assistance and, most dramatically, making Ukraine a candidate for EU membership, are policies that the UK government has supported and in which it has a strong interest in seeing success. The UK position on the EU’s defence industrial strategy, which has been accelerated as a consequence of Russia’s war, is rather more ambiguous as it is concerned that non-member states face exclusion from EU programmes.

The relationship with the EU might change under an incoming government. The opposition Labour Party, currently significantly ahead of the Conservative Party in public polling intentions for the next General Election due by early 2025, is seeking a ‘security pact’ with the EU. And a security and defence partnership with Germany akin to the Lancaster House agreements the UK has in place with France covering bilateral security and defence cooperation. These developments would represent a significant change in the mood of EU-UK relations but they would not likely have a profound effect on the broader posture of UK security and defence policy.

Thought leader

The UK views itself as a security and defence thought leader in Europe. Its thinking on the European security is currently predicated on a number of elements. First, that NATO is the only viable arrangement for collective security and defence in Europe. Second, that any initiatives by Europeans outside NATO should serve the purpose of enhancing the capabilities and credibility of the transatlantic alliance. Third, that European and Indo-Pacific security and stability must be considered conjoined. Fourth, that as Russia remains, in the words of the IR, ‘the most acute threat to the UK’s security’ the British view is that all European states need to make the necessary adjustments in thinking that have the consequential effects of raising defence spending, focusing on capabilities enhancement and with the deterrence of Russia requiring a response embracing all domains encompassing conventional and unconventional warfare, and nuclear deterrence. With the UK position as a European nuclear weapons possessing state the nuclear deterrence of Russia has a salience absent in other European states security debates. The UK’s position on re-establishing arms control arrangements in Europe and reform of collective security arrangements such as the Organisation for Security and Cooperation in Europe (OSCE) would be predicated on its perception of Russia’s pernicious role in flagrantly discarding past agreements.

All of this UK positioning, however, faces a significant challenge with a prospective change of President in the United States. The UK is heavily intertwined diplomatically, militarily and crucially in the intelligence field, with the United States. Consequently, a radically altered perspective in the White House on the transatlantic relationship would be a challenge for the UK of a greater order of impact than for the majority of European states.


Future UK governments (of whatever political persuasion) will see themselves in the role of a key player in forging Europe’s future security architecture. However, their preference for a strong transatlantic relationship at the heart of that architecture may be the most challenging element to maintain in the future. Demonstrating the benefits to the U.S. that accrue from NATO whilst cajoling European states to take on greater security and defence capabilities will be a likely British response to future U.S. administrations that are more willing to question the utility of a military alliance with Europeans.

If European security arrangements had to be contemplated with a greatly diminished contribution by the US, the UK would envision a different proposition from the idea that the EU might represent a future vehicle for European collective security. The UK preference would likely be to seek to maintain and enhance its existing network of bilateral and minilateral security and defence relationships as the underpinning of collective security arrangements with like-minded European states. The UK’s instinct would be to maintain a preference for Euro-Atlantic security arrangements between European states that are organised for a shared collective purpose (rather than the proposition that European security and defence should be directed through supranational arrangements).

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The views and opinions in this article do not necessarily reflect those of the Heinrich-Böll-Stiftung European Union.