Securing Ukraine is the UK’s Challenge, but It Needs to be Done Right

The series of shocks that the Trump administration delivered on European security over the past week has left the continent’s leaders reeling. The Trump–Putin telephone call and Secretary of Defense Pete Hegseth’s comments on how the US will approach negotiations to end the Ukraine war and European security more generally have caused widespread alarm. This has only been deepened by the news over the weekend that the US is pressing ahead with direct negotiations with Russia in Saudia Arabia – without the Europeans, and only in loose contact with Ukraine. The tectonic plates of European security have shifted, and European countries appear to have little influence on developments.

French President Emmanuel Macron has convened an emergency summit in Paris. The panic created by the Trump administration’s actions suggests that European leaders finally understand that they need to get serious about defence after years of promising to raise investment in their militaries but failing to deliver. UK Prime Minister Keir Starmer has spoken of a ‘once-in-a-generation moment for our national security’. But what are the Europeans going to propose? The US statements have pulled away the curtain on European security to reveal not just that European countries have drastically underfunded their own defence for decades, but also that they are largely bereft of a strategy for European security with a reduced US engagement, and short of the leadership to set a direction.

At this moment of acute anxiety, there is a real risk that Europe will attempt to fill the security void with rash and ill-thought through proposals. The immediate challenge is to identify how Europe can support Ukraine’s future security. There is a gathering momentum behind the idea that Europe must deploy military forces to Ukraine as ‘peacekeepers’, which in fact will mean a peace enforcement and deterrence force. Ahead of the Paris summit, Starmer has indicated that the UK is ready ‘to contribute to security guarantees to Ukraine by putting our own troops on the ground if necessary.’ This would be a mistake.

European Security Guarantees for Ukraine

As early as February 2024, Macron raised the issue of European boots on the ground. Subsequently, there have been regular reports of discussions about a European peacekeeping mission to Ukraine. In recent weeks, these reports have intensified as concern grew about what the Trump administration was planning for Ukraine. Following the recent US statements, there have been calls for substantial European ground forces to be deployed to Ukraine. Now, the US has asked European countries to indicate what they are ready to commit to ensuring Ukraine’s future security. 

Ukrainian President Volodymyr Zelensky has spoken of a need for 200,000 foreign troops as a security guarantee. Media reports suggest that plans have been considered for a ‘robust’ European force of 30,000-40,000 troops, with accompanying air support, to consolidate the peace and deter Russia from future attacks against Ukraine along the 1,000 km front. With little realistic prospect of a force of the size that Zelensky has called for, in fact, the presence of European troops would have to be considered primarily as a tripwire force. So, by making such a security commitment, Europe would have to be prepared  to escalate to a full-scale war with Russia in Ukraine, and possibly on a wider front, in the event that its ‘peacekeeping’ forces come under attack.

Despite the talk of peace, Russia will continue to view Ukraine as a target for its expansionist policies and will rebuild its military forces following any agreement. European forces in Ukraine would, therefore, be operating in a hostile and fragile environment with a high risk of becoming involved in combat with Russia at some point. Russia has already signalled that it would consider any foreign force in Ukraine a legitimate military target, unless it was part of a UN Security Council-sanctioned mission. Hegseth was clear in his comments that any force in Ukraine ‘should be deployed as part of a non-NATO mission. And they should not be covered under Article 5.’ When deploying troops to Ukraine, Europe would thus have to be ready to fight a nuclear superpower without the backing of the US and its extended security guarantee.

Even if such a European force did not become involved in a war with Russia, an open-ended commitment to Ukraine of this scale – potentially lasting many years – would inevitably become the main focus for European countries’ defence efforts, pulling forces from other theatres and draining military resources at a moment when there is an urgent need to reconstitute European militaries in the face of an enduring threat from Russia that stretches far beyond Ukraine.

Such a deployment would thus risk becoming a trap. In the best-case scenario, it would lead to severe overstretch of European forces and an over-focus of resources on one sub-regional theatre. In the worst case, it would allow Russia to pull Europe into fighting far from its core logistical bases, at a time when European forces are desperately short of mass and when they would be lacking backup from US forces and their key enablers which are essential for joint warfighting.

Biden’s Ukraine ‘Porcupine’ Security Plan Remains the Most Realistic Option

Instead, Europe should double down on the commitments that it has already made to Ukraine. At the NATO Washington summit in July 2024, President Joe Biden launched the Ukraine compact. Building on the G7 long-term security commitments to Ukraine made on the margins of the Vilnius NATO summit the previous year, the Ukraine compact brought together over 20 bilateral security commitments, including from countries in Europe and the Indo-Pacific. This is also the framework for capability coalitions to drive the future development of Ukraine’s armed forces.

The existing security compact should be Europe’s starting point for security commitments to Ukraine. European countries should now take over leadership of the compact as the principal means to provide training and weapons to Kyiv, to develop Ukraine’s defence industry, to share intelligence, and to promote interoperability. The aim should be to work with Ukraine to ensure that it has all that it needs to develop and sustain its own future force which would be capable of deterring Russia, building on its existing battle-hardened troops. This will require not just European leadership but also a long-term political and financial commitment to develop the compact further as a key mechanism of European security.

Such a commitment also gives European diplomacy a focus in the upcoming peace negotiations with Russia. Moscow must not be allowed to dictate a demilitarisation of Ukraine or enforce neutrality on the country – even if the US indicates that NATO membership for Ukraine is not possible. Ukraine must be allowed to retain sufficient armed forces to protect itself and be able to modernise these forces, and Europe should commit to supporting these efforts in the long term.

The UK, Ukraine and European Security

The UK has been a firm supporter of Ukraine since the beginning of the war, providing vital military, economic and diplomatic assistance, helping to mobilise wider support, as well as concluding a 100-year partnership with Kyiv. Now, when the UK has just taken over chairing the Ukraine Defence Contact Group (the Ramstein group), is the moment for the UK to offer its leadership of the Ukraine compact in place of the US as the means to rally and steer collective European efforts to provide Ukraine with the resources that it needs to build its defence and deterrence for the long term.

London needs, though, to recognise that a potential settlement of the war in Ukraine is not just about Ukraine. A peace agreement will not mark the end of conflict with Russia, but rather the transformation of the confrontation into something much broader, more long-lasting and potentially more threatening as Russia looks to reconstitute and expand its military. An end to the fighting in Ukraine will highlight that the principal threat to the UK from Russia does not come from an attack against the eastern flank, but from Russian forces in the vast area stretching from the Arctic and High North to northern Europe and the Baltic states. 

Much of Putin’s powerful northern fleet and his key nuclear forces remain intact in the region and are focused on breaking into the north Atlantic and threatening the UK and its allies, including through grey zone actions. Putin has made clear his ambition to expand Russia’s armed forces in this region. For London, this sub-regional space will be the key theatre where it will need to concentrate its defence resources and invest in new capabilities, just as the US is pivoting away from Europe. With the defence budget likely to increase only marginally in the years ahead, commitments to Ukraine will need to be balanced with the priority of protecting the homeland. 

The Trump administration has reportedly indicated to the Starmer government that the UK should now take on a larger leadership role on European security. The UK is well-placed to help to fill the gap as the US focuses more on the Indo-Pacific, but it will also need to be clear about what its own European security interests are and where the principal threat to those interests lies. Committing troops to Ukraine would be an over-extension of military resources, exposing the UK to a war with Russia in Ukraine that it is ill-prepared to fight, and would risk leaving the UK vulnerable to Russian threats from the north. A strategy, however, that strengthens UK efforts together with others to build Ukraine’s own defence capabilities, alongside further investment in the UK commitment to northern Europe and the Atlantic would help to stretch Russian forces, preventing Moscow from concentrating on one sub-region, and would thus be a key commitment to collective European deterrence against Moscow.

© RUSI, 2025

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