Far from making the future safer, a ceasefire in Ukraine may both make the threat from Russia more immediate and render Western European states even less willing and able to rebuild their own defences.
Interests
The UK’s 2025 National Security Strategy notes that: ‘In supporting Ukraine, our essential goal is to prevent further Russian aggression.’ In the event of a suspension of hostilities in Ukraine, the primary imperative for Europe and the UK is still to maintain deterrence of Russia to reduce the probability of a further overt attack, whether in Ukraine or elsewhere.
This forms part of the broader fundamental European interest in maintaining peace and stability across the continent, to the greatest extent possible in the face of its primary security threat: Russian determination to reassert power over its immediate vicinity and continue a campaign of sub-threshold attacks elsewhere, including cyberattacks, sabotage and disinformation.
Nevertheless, this core interest for Europe presents dilemmas in the context of continued dependence on a weakening transatlantic relationship, and the clear preference of the Trump administration for outcomes in Ukraine that will meet Russian approval.
It is unclear at present how European states could realistically assume the role of a security provider for Ukraine – and be recognized as such by a sceptical US administration, and by extension Russia – without a seat at the negotiating table and without the necessary leverage to enforce commitments.
But with or without the US, protecting and preserving Ukraine, its society and its economy, and the lives and livelihoods of its people, forms an important subset of the overall objective of fostering continued security and resilience across the European continent.
It follows that the risks to Europe enumerated in the next section are in addition to, not instead of, those in the earlier chapter on Ukraine that will have direct spillover effects on European security as a whole, such as slow economic recovery or the perennial likelihood of Russia resuming the war. The new security environment that would emerge as a result of an inconclusive suspension of Russia’s war on Ukraine has the potential to define European security over the long term, with profound economic and social consequences.
Risks
Russia attacks Europe
Russia’s core objectives, to reassert Moscow’s control and sphere of influence over the states along its western perimeter, and to reorder the post-Cold War European security framework, are unlikely to change as a result of a ceasefire.
Any end to major combat operations in Ukraine will free Russian armed formations to redeploy and reconstitute, which will proceed at a faster pace if they are no longer destroyed by Ukrainian forces almost as swiftly as they are rebuilt. In addition, while Russia has shown no interest in ending the war despite the undeniable costs to itself, a suspension of major combat operations would also relieve some of the pressure on Russia’s economy, boosting its economic outlook and government budgets. This positive effect would be all the greater if European states – whether under pressure from the US or genuinely (but mistakenly) believing the war to be over – lift some or all of the sanctions burden from Russia.
All of this would further encourage Russia to continue its assertive foreign policy. A Russian perception of success, combined with Moscow’s need to continue conflict to maintain its system of governance, could mean that a ceasefire in Ukraine brings forward the date of the widely-anticipated next Russian attack on Europe. But the nature of the ceasefire agreement, and in particular the restrictions that it places on Ukraine, will determine how free Moscow is to act elsewhere. The greater the advantage Russia is granted in Ukraine, the greater the threat and the earlier the danger for the Kremlin’s next victim.
Estimates continue to vary regarding when Russia will be ready to resume open warfare, either on Ukraine or against a NATO member state. But the one thing these predictions have in common is that an attack is likely to occur before Europe can be ready to defend itself. Even without any earlier sudden collapse of transatlantic security arrangements, European countries are ill-prepared for a mooted 2027 deadline for the US to reduce or remove support for European defence.
False perception
In the immediate aftermath of an agreed ceasefire, there is a risk that European leaders and publics may assume that their security environment has changed for the better, whereas in reality the threat would become substantially more immediate. Polling of European opinions on the war at the end of 2025 showed that many in Europe were aware that Russia could restart a conflict in Ukraine or attack other European countries, but those polled still believed Ukraine could negotiate an end to the war.
There is a risk that a negotiated ceasefire could be confused with a settlement of the conflict, and thus persuade Europeans that the challenge to their defence and security has been resolved.
However, there is a risk that a negotiated ceasefire could be confused with a settlement of the conflict, and thus persuade Europeans that the challenge to their defence and security has been resolved. Combined with the perception that defence and security spending has been increasing in Western Europe, and the widespread view there that support for Ukraine has been sufficiently strong throughout the war, this would only deepen the risk of dangerous complacency over future threats. For example, Italy’s foreign minister has already suggested that in the event of a ceasefire, Ukraine would not need any more arms supplies.
Deterrence
In the event of a ceasefire, European leaders will face a political argument, augmented by voices on both the left and right, that the urgent need for investment in rearmament is no longer there and thus defence spending should be curtailed or planned increases shelved. (Insistence by the US that European defence spending should continue to increase has been met in some cases by pretence rather than action, even after the demonstration of shifting US intent in the form of threats to Greenland.)
Acceptance of a flawed agreement could be driven by the reasonable, but incorrect, assumption that a ceasefire is a better and cheaper option in the long term than supporting Ukraine to the maximum extent possible to continue fighting and resisting – and ultimately defeating the Russian invasion. Instead, the cost of future collective security against threats from Moscow will continue to increase as the US recalibrates its contribution to European defence. New procurement instruments, such as the EU’s Security Action for Europe (SAFE) initiative and NATO’s Prioritised Ukraine Requirements List (PURL), will still need to be funded – but European contributors will face pressure to reduce commitments.
In addition, despite US assurances that its policy of extended deterrence will continue for as long as European defences remain insufficient, reduced confidence in US guarantees combined with the probable resumption of Russian encroachments means an increased risk of nuclear proliferation as states consider development of sovereign non-strategic nuclear capabilities.
Sanctions and energy
An end to major combat operations in Ukraine would lead to pressure on European states to lift sanctions on Russia. This pressure would come both from domestic actors with economic interests in Russia, arguing that in the absence of war the burden of sanctions is unnecessary, and from the US seeking to restore the business relationships of its elites with Moscow. European states would also be faced with the temptation to once again increase imports of Russian energy over the long term, recreating a dangerous dependence – with a primary alternative of depending on an equally unpredictable US for energy.
Population
Europe will also face a challenge in the form of population movements after a ceasefire. Consolidation of Russian control over the occupied regions – or the potential of a peace settlement to grant Russia control over Ukrainian territories not yet occupied – would trigger a further wave of displaced Ukrainians seeking escape.
In addition, a reduction in hostilities could see former combatants from both armies flowing into Europe, especially if travel restrictions are lifted. Russia is already suffering the effects of traumatized and brutalized soldiers returning into communities, and the same effects could become more widespread across Europe. Some members of the Ukrainian diaspora have already been targeted for recruitment or coercion by Russia into covert attacks on their host nations; and this trend could increase after Ukrainian combat veterans travel to Europe to rejoin their families already residing there.
Ceasefire terms
There is no indication at present that European leaders recognize the challenge of ensuring that a ceasefire constitutes a path to a durable peace settlement, rather than providing an opportunity for Russia to reconstitute its land forces. The most recently released draft terms of a ceasefire at the time of writing suggest that any violation would lead initially to a diplomatic response by the supposed guarantors of peace, and only after further escalation would trigger potential military intervention by foreign forces.
If implemented, a plan of this nature would allow Russia to carefully calibrate its ceasefire violations to ensure that responses remained verbal rather than kinetic – and thus discredit both the ceasefire and the European forces notionally assuring it. The experience of the OSCE Special Monitoring Mission (SMM) to Ukraine, and the EU Monitoring Mission (EUMM) in Georgia, shows how European supranational organizations can be left burdened with the responsibility and cost of monitoring a non-viable ceasefire, with no means of enforcement and thus no way of deterring constant violations (see Chapter 5).
Unity
European unity is already under severe strain despite a clear and present threat from Russia, and tensions are likely to rise further after a ceasefire if countries dispute whether that threat remains. Disagreements between frontline states and the European hinterland over not just the need for defence, but also the defence and economic integration of Ukraine into Europe, will be exacerbated.
The same conflicting priorities may fuel disagreement over the nature of any possible new collective security arrangements intended to compensate for the reduction of the US role in NATO. A temptation to focus on score-settling and competition between European states instead of collective survival – exposed by the manner of the UK being frozen out of the SAFE collective procurement programme – may be even more prominent in the European security debate. It will also be harder to maintain international initiatives such as the ‘coalition of the willing’ if it comes to be widely believed that the threat has receded.
However distasteful some European states may find the prospect of reinvigorated contact with Moscow, the alternative is continued reliance on the intermediacy of the United States, which will prioritize US elite interests rather than those of Ukraine’s neighbours and partners further afield.
In addition, a unified approach to Russia will continue to be challenged by debate over whether Europeans need to develop their own diplomatic channels to Moscow. However distasteful some European states may find the prospect of reinvigorated contact with Moscow, the alternative is continued reliance on the intermediacy of the United States, which will prioritize US elite interests rather than those of Ukraine’s neighbours and partners further afield.
Assurance forces
Despite its professed hostility to the idea of European forces being based in Ukraine as an assurance force, Russia might be entirely content for a significant proportion of Europe’s deployable forces to be tied down in Ukraine and thus not able to defend elsewhere.
Nevertheless, current plans for placing foreign forces in Ukraine to provide support after a ceasefire still relate to a situation that is both hypothetical and unlikely; hypothetical because no ceasefire is currently in prospect, and unlikely because if there were an agreement, the probability that its terms would allow the presence of a foreign force in Ukraine is low.
If this situation does arise, however, both European resolve and capabilities will be swiftly put to the test. In underwriting a ceasefire in Ukraine, European nations would take on substantial risk, with critically limited resources to mitigate it, in exchange for benefits that are at best fragile and temporary.
British announcements of plans to contribute to an assurance force have generated not just scepticism but bewilderment among defence commentators. With the UK falling rapidly behind in terms of military spending, as well as capability, relative to the rest of the continent, observers have questioned how such a force can be expected to defend itself against Russian probing and testing, which is considered inevitable.
In January 2026, Russia stated again that foreign military units and facilities in Ukraine would be ‘considered legitimate combat targets’. The text is familiar boilerplate, but Russia could reasonably calculate that a joint European force in Ukraine could be too lacking in offensive capability, and its rules of engagement too restrictive, to respond to Russian provocations. This would risk leading to a loss of credibility for the European force, combined with calls for its withdrawal as the risks become clear. Such an outcome would be a more damaging course of action than not having deployed it in the first place.
‘Security guarantees’
The deployment of an assurance force is tied to an assumption that the US would provide additional security guarantees. However, doubt over when any such guarantee would be implemented is augmented by the repeated pattern of Russia influencing Donald Trump’s understanding of what is happening in Ukraine – as with claims of Russia’s capture of key objectives at crucial moments in negotiations, such as Kupyansk in early December 2025. Even when the effect of deceiving the US leadership is temporary, it lasts long enough to affect diplomatic processes, which may be all that Russia needs. In addition, according to Donald Trump, US support is predicated on the assumption that Russia will not breach the ceasefire, which is the opposite assumption to that held by credible observers of Russia.
Implications
All of the risk factors to Europe listed above, together with those in the Ukraine chapter, have remained largely unchanged since Chatham House published a multi-author report in mid-2023, which described in much greater depth how ‘a ceasefire or “negotiated settlement” to end the fighting without tackling its underlying cause – Russia’s ambition to eliminate Ukraine as we know it – will do no more than reward the aggressor while punishing the victim’. It is only since the return of Donald Trump to power in the US that a temporary ceasefire has vaulted from being one of the worst case scenarios for Ukraine to being one of the least worst.
Freezing the conflict with any notion of territorial concessions by Ukraine risks handing Russia the victory it has been unable to attain through military means since 2014.
Freezing the conflict with any notion of territorial concessions by Ukraine risks handing Russia the victory it has been unable to attain through military means since 2014. Russia’s continued, and often successful, efforts to convince credulous audiences abroad that its victory is inevitable is a key component of its attempts to achieve its objectives by political means. These efforts may succeed, with the assistance of a receptive US. However, European states, especially those most at risk, will continue to emphasize that security against Russia is essential. This presents the prospect of further worsening transatlantic discord.
In circumstances where some Western European governments continue to claim that rearmament plans and NATO commitments are unaffordable, confusing a ceasefire with lasting peace would provide a dangerous temptation to ease off defence spending. In addition, the unifying factor of preserving Ukraine and its borders could be lost from the common European security endeavour if governments consider the matter settled, risking a loss of impetus for cooperative defence arrangements. Nevertheless, it is vital that optimism, or relief at a suspension of fighting, should not distract from the fact that the cost of defending Europe will increase drastically, not decrease, if Ukraine is neutralized or rendered unable to withstand future Russian attacks.
The future relationship with the US will be fundamental to Europe’s ability to manage the aftermath of a ceasefire. Conversely, how Europe manages this will also directly impact relations with the Trump White House, which is determined to normalize relations with Russia and reduce the role of the US as a guarantor for Europe.
But Europe will remain hostage to the US’s understanding of the European security situation, which can at times be quite distant from reality. Donald Trump, for example, continues to insist that Putin ‘wants to end the war’. In addition, the repeatedly demonstrated willingness of the Trump administration to disregard or forgive Russian aggression – including violations of agreements such as the supposed ‘energy ceasefire’ in late January 2026 – call into question the value of any ceasefire agreement that has been made conditional on US security guarantees.
Furthermore, Russia would be entirely capable of engineering a collapse of a ceasefire, and blaming Europe, in order to sow mistrust in the transatlantic relationship and further erode US support for Europe. Meanwhile, Europe will be under pressure from the US to normalize relations with Moscow regardless of assessments of Russian threats to European capitals.
Overall, Europe should be in no doubt that a ceasefire agreement in Ukraine, far from resolving the continent’s primary security threat, will only make it more challenging and complex.
