This commentary is part of the European Leadership Network’s special coverage of the 2026 NATO Summit, which will take place in Ankara on 7-8 July 2026. The series brings together expert voices to examine the key security challenges, strategic questions, and policy debates shaping the future of the alliance before and after the summit.

European security architecture is at a crossroads. NATO and the EU are searching for new roles as European governments respond to growing uncertainty over the future of transatlantic security. There is space for new ideas, although the timeframe, given the current security environment, is short. NATO Secretary General Mark Rutte and several Western intelligence services have warned that, if current military rearmament continues, Russia could have the capability to launch a larger conflict with NATO before 2030.

While there is some disagreement among allies about the severity of this threat, there is consensus on the need for European states to adapt so they are better able to defend themselves. Consequently, European states are radically increasing their defence budgets, developing cooperation on procurement, and building new partnerships. In fact, military spending by European NATO members surged last year at its fastest pace since 1953.

Former Finnish President Sauli Niinistö has led a task force to examine concrete alternatives for European security should US commitment to NATO diminish. Titled More Europe in Defence: Three Pathways, the report outlines three different structural paths for Europe’s future security architecture. It is the product of independent research carried out by the think tanks CEPS, Clingendael, IEP and RUSI.

The first path is a more European NATO. Under this approach, cooperation with the US would continue in the most critical areas while the European role is strengthened. European member states would commit to spending 3.5 percent of GDP on direct military capabilities and 1.5 percent on indirect investments in non-military security by 2035. NATO command structures would become more European, although the Supreme Allied Commander would remain American in order to maintain the link to US ground forces and nuclear capabilities.

The second path addresses the possibility that the US, or another ally, could block cooperation within NATO structures. In such a scenario, a new institution – such as a European Security Council – could be established to facilitate political decision-making and consultations outside NATO’s consensus requirement. Proposed members include NATO’s Secretary General, as well as the presidents of the European Commission and the European Council.

The third path envisages European defence under the EU. This would build European defence around the EU’s mutual defence clause, under which member states are obliged to assist any member that comes under armed attack. The clause would be clarified to strengthen cooperation, while European defence industries would be better aligned with common strategic interests. This would include investing in Ukraine’s defence industry and integrating it into the European market. The approach would complement NATO’s Article 5 while advancing a greater degree of European strategic autonomy and sovereignty in relation to the US.

Taken together, the report maps the spectrum of possible European security arrangements and offers policy recommendations on the choices facing Europe’s future security architecture.

Another critical question concerns the nuclear umbrella. How will Europe’s non-nuclear-weapon states be defended in the event of a nuclear strike or even a limited nuclear war?

NATO’s Article 5 has long created the expectation that this decision would rest with the US and that American nuclear weapons would protect European NATO allies. The credibility of that assumption has now been called into question, creating particular uncertainty in NATO’s newest members, Sweden and Finland, as the US appears increasingly reluctant to shoulder responsibility for European defence. Although recent US presidents have all expressed doubts about the nuclear implications of the so-called “musketeer clause” – an informal nickname for NATO’s Article 5 – the issue has become increasingly urgent in light of Russia’s periodic nuclear threats during the war in Ukraine.

European states are therefore exploring new solutions. In Poland, debate has expanded beyond hosting allied nuclear weapons to include discussion of whether the country should eventually develop an independent nuclear capability. Finland has moved to repeal its longstanding legal ban on nuclear weapons in order to align fully with NATO’s deterrence posture, while continuing to rule out hosting nuclear weapons in peacetime. Elsewhere, including in Germany and across the Nordic states, discussion has focused primarily on closer integration with NATO’s nuclear posture and possible participation in a future European deterrent led by France and the UK.

A more viable alternative has been proposed by France and the UK, Europe’s two nuclear-weapon states. These proposals reflect growing efforts to build European strategic autonomy in response to mounting security concerns. Together, French and British nuclear forces could form the basis of a European nuclear umbrella. At least initially, this would complement rather than replace NATO’s existing nuclear deterrent. The framework would allow European allies to participate more closely in French strategic planning while enabling participating countries to host French strategic air forces temporarily and take part in joint nuclear exercises.

Nine European states have already joined discussions on France’s “forward nuclear deterrence” doctrine: the UK, Germany, Belgium, Poland, Greece, the Netherlands, Sweden, Denmark and Norway. Finland is currently holding informal discussions about joining. Fear of Russian aggression and uncertainty about US commitments are increasingly motivating these countries to seek alternative forms of deterrence. The resulting agreements are bilateral, between France and each participating country, and vary in their degree of transparency. There is an urgent need to clarify how forward deterrence would be implemented in a way that complements NATO’s existing deterrence posture.

At the NATO summit, the future of the alliance will be discussed in terms of a “NATO 3.0” based on partnership rather than dependency. In this context, there will undoubtedly be discussion of the Europeanisation of NATO. This debate will be politically sensitive, as the recent US National Security Strategy calls into question longstanding assumptions about America’s commitment to European defence, while European countries are not yet capable of fully compensating for a reduced US role.

From a European leadership perspective, it is important that this discussion does not obscure political disagreements behind technical debates about defence spending, burden-sharing, and military capabilities. European leaders need the freedom to articulate a collective vision for a cooperative European security order, ideally in partnership with the US. If necessary, that vision should extend beyond the Europeanisation of NATO in order to give European citizens something to rally behind. A recent study by the Bertelsmann Stiftung suggests that more than 70 percent of Europeans believe Europe should “go it alone” after decades of close cooperation with the US.

NATO Secretary General Mark Rutte has said that the alliance is not “whistling past the graveyard” but entering “a period of profound change”. Understanding what that means requires an open, honest, and constructive discussion of both common interests and genuine differences. That conversation needs to begin in Ankara.

The European Leadership Network itself as an institution holds no formal policy positions. The opinions articulated above represent the views of the authors rather than the European Leadership Network or its members. The ELN aims to encourage debates that will help develop Europe’s capacity to address the pressing foreign, defence, and security policy challenges of our time, to further its charitable purposes.

Image credit: Keith Anderson / US Department of War