Since Donald Trump’s re-election, the mood in European capitals has been one of foreboding. Although his second-term foreign policy priorities remain vague, his past pronouncements and historic hostility toward alliances suggest that Europeans may soon have to reckon with a sharp shift in American attention and resources away from Ukraine and the Middle East, and towards China.  

If America’s commitment to transatlantic security is indeed called into question, European countries must be in a position to deter, and if necessary defend themselves against, military threats – primarily from Russia, but potentially also from further afield. Since no proper defence of Europe is conceivable without support from the United Kingdom, the new Labour government under prime minister Keir Starmer must act decisively to boost the country’s support for Ukraine, strengthen bilateral security alliances with key European Union member states, and deepen its defence co-operation with the EU itself. 

Britain’s strategic dilemma 

Trump’s election poses a dilemma for Starmer’s government. Britain has long profited from its ‘special relationship’ with the United States, especially in the form of intelligence sharing and access to advanced technology. But aligning itself more closely with the US than Europe would be a mistake. In 1944 Winston Churchill told Charles de Gaulle, “You must know that when we have to choose between Europe and the open seas, we will always be with the open seas.” But Trump’s America is hardly Roosevelt’s. And as the US becomes increasingly isolationist, focuses on all-out competition with China, and abandons multilateralism and free trade for a more protectionist doctrine, partnering with the EU will come much more naturally to the UK. Closer values aside, Britain’s geographical reality makes drawing closer to the EU and its members less a choice than a strategic imperative – even if it risks incurring Trump’s ire. 

The government has already signalled that it favours a closer relationship with Europe. Since taking office in July, Starmer’s actions include hosting the European Political Community summit at Blenheim Palace, pursuing bilateral meetings with European leaders including European commission president Ursula von der Leyen, and foreign secretary David Lammy’s participation in the EU Foreign Affairs Council. More substantively, the UK and Germany signed a historic defence and security agreement in October.  

Defending Ukraine comes first 

But if Britain is to transform its relationship with Europe in a more meaningful way, it must use the coming months to boost its support for Ukraine, intensify its bilateral defence relationships with EU member states, move full steam on a security pact with the EU – and even start to envision a European dimension to its nuclear deterrent. 

The war in Ukraine and heightened potential for Russian aggression is the most immediate threat to European – and by extension, British – security. If Trump intends to force Ukraine into a settlement, as intimated during his presidential campaign, the UK should work with its European partners to maximise Kyiv’s leverage in any upcoming negotiations. Allowing Ukraine to use storm shadow missiles in Russian territory was a good first step: now Starmer should encourage his counterpart in Germany, chancellor Olaf Scholz, to send his country’s own Taurus missiles. 

If Trump abandons Ukraine after a hypothetical peace deal, the UK should be prepared to deploy troops to act as a tripwire and security guarantee – possibly as part of a Joint Expeditionary Force (JEF) mission.  

Strengthening bilateral relationships 

In the medium term, the UK must deepen its bilateral relationships with individual European countries in order to expand co-operation and interoperability between defence and industry. The Trinity House Agreement sees Germany and Britain pledge to do just that; Britain has a similar agreement with France, but the relationship still punches below its weight. Much of the connective tissue which existed prior to Brexit is gone and, in the NATO context in which much of the Franco-British defence interaction takes place, Paris is primed to view London as an American Trojan Horse. 

The UK should therefore work to improve interoperability between the two countries’ armed forces and rebuild lost trust, with a view toward eventually developing a unified approach to defence-industrial questions. Retooling the 10,000-strong Combined Joint Expeditionary Force (CJEF) to make it relevant in today’s warfighting context could be a first step in breathing life back into the relationship between Europe’s two most serious military powers. 

There is also potential for the UK to develop its relationship with Poland, the highest NATO defence spender in relation to GDP and increasingly a leader in European security efforts. In 2023, the two countries signed the 2030 strategic partnership joint declaration on foreign policy, security, and defence – but they could go further, moving toward a “privileged partnership” similar to the one London has with Berlin and Paris. Indeed, according to Polish officials[1], the appetite for such an agreement is high. The incoming Polish EU presidency is already taking the lead in organising an upcoming EU-UK summit – pencilled in for early next year, this could serve as an ideal platform to announce an agreement.

In the most optimistic scenario, these treaties could create a latticework which binds together the biggest European defence actors to act as force multipliers for Europe’s collective defence. But Britain could also deepen its co-operation with smaller, northern European countries through the JEF, which could prove useful in providing security guarantees for Ukraine. At the same time, it should avoid including issues related to freedom of movement and trade in any bilateral deals it makes, lest these give the appearance of encroaching on the remit of the European Commission. 

Toward a security pact 

While strengthening ties with individual European countries, the UK should also work with the EU to speed up negotiations on a more focused security pact. From what has been made public, the pact is currently being conceived of in the broadest sense possible, with chapters on energy, critical minerals, telecommunications, health, and migration. These are crucial to restoring the post-Brexit EU-UK relationship: but the current situation demands urgency and prioritising the ‘hard security’ elements of the pact. 

Instead of immediately seeking the same sort of legal agreement with the EU as it has with countries such as Canada or Japan – which all member states and possibly the European Parliament would have to ratify –  the two sides should first aim for a joint declaration. A solid, agreed-upon framework would then allow the two sides to move forward on key issues such as defence-industrial co-operation. 

Furthermore, the UK should put its money where its mouth is and pursue negotiations in a way which will build back trust within the bloc. Many European officials harbour residual suspicion of the UK’s cherry-picking antics during the withdrawal negotiations: if the UK wants to signal that it truly means business, it must be willing to contribute financially and meaningfully to initiatives such as the European Defence Fund (EDF).[2]

Finally, given a potential decline in America’s commitment to European security, any closer defence relationship between the UK and Europeans must include a nuclear component. Britain is a nuclear weapon state; its arsenal can provide a concrete and unique contribution to European collective security. Strategic consultations on nuclear issues with European allies would be a sensible first step, as would considering adapting Britain’s nuclear position to account for the (still far-fetched) scenario where France and the UK might need to replace America’s nuclear umbrella. 

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Cooperation between the UK and the EU is one piece of a much bigger puzzle; there are plenty of obstacles to making wider Europe a credible defence actor. Europeans will have to overcome their lingering suspicion of the UK and accept that it is fundamentally different from a third country like Norway or Canada in its potential contributions to European security, especially when it comes to green-lighting its participation in EU defence schemes. 

Ultimately, however, the ceiling for UK-EU co-operation on defence is as high as EU leaders want it to be. What has been missing until now is the political will to transform the relationship – but Trump’s re-election is providing both sides with the required momentum. 

[1] According to the author’s own conversations with Polish government officials

[2] Based on the author’s conversations with French, Polish, and British government officials