This year, German Chancellor Friedrich Merz, Polish Prime Minister Donald Tusk, and others have raised a long-suppressed question: What if the United States cannot be relied upon to provide extended nuclear deterrence to NATO allies? Despite reassurances that U.S. commitments remain unchanged, Europeans have been working behind the scenes to meet the moment.

Signals from U.S. President Donald Trump that Washington may reduce its commitment to Europe continue unabated. The new U.S. National Security Strategy, urging Europe to “stand on its own feet,” is only the latest indication of a break with the traditional American approach to defense on the continent. But even in a friendlier political climate, structural shifts will challenge the credibility of U.S. security commitments as Washington prepares for competition with two nuclear peers, Russia and China, for the first time. Emerging nuclear multipolarity makes the classic extended deterrence model harder and riskier to sustain. 

Understanding how the European deterrence debate has evolved in response to these obstacles requires recognizing the fundamental challenge that it must do three things for three distinct audiences: deter Russia, assure allies on the continent, and keep the United States engaged.

While U.S. nuclear weapons have historically played a key role keeping Moscow in check, Europe has begun investing in new conventional capabilities to help reinforce that deterrence. One example is the European Long-Range Strike Approach, a joint effort to build and deploy long-range precision missiles. It will not deter Russia on its own, but it can strengthen efforts to do so by complicating Moscow’s operational planning and reducing its confidence in rapid or low-cost gains. 

Yet, even with sustained investment, Europe’s deep-strike capacity will take the next decade or more to mature. Key enablers—such as intelligence, surveillance, and reconnaissance networks—remain insufficient, while industrial bottlenecks and supply chain constraints continue to slow progress.

What is more, Europeans must clarify what these strike systems are intended to do, what kinds of targets they should threaten, and how they relate to NATO’s nuclear posture. Without clear alignment on doctrinal signaling, Russia could misread these nascent capabilities as threatening its own nuclear arsenal—increasing the risk of escalation and conflict rather than reducing it.  

Alongside this, allies needs credible assurances that deterrence will hold in the face of political and structural pressures. Today’s uncertainties increase the risk that some states, such as Poland, could doubt the reliability of security guarantees and may in turn contemplate independent nuclear options. Such proliferation would not only undermine the global order but also fracture Europe’s security cohesion. Instability would also likely grow during the years it takes a state to build a survivable arsenal, forcing other European countries (and the United States) to decide whether to protect that proliferator from Russian retaliation.  

The two existing nuclear powers in Europe—the UK and France—are playing an increasingly important role in addressing this problem. 

The UK announced this year that it will purchase American F-35A fighter jets and join NATO’s dual-capable aircraft mission, while France opened a “strategic debate on the protection of [its] allies on the European continent by [its] deterrent.” In the Northwood Declaration, London and Paris jointly affirmed a European dimension to their vital interests. They declared that their nuclear arsenals can be coordinated—the first such indication from France—and announced a new Nuclear Steering Group to deliver on that coordination.

The assurance signal is clear: Both countries recognize the role of their nuclear capabilities in contributing to the security of Europe. They could build on this momentum in the coming year by engaging in regular consultations with allies, but to have the greatest effect, they will have to overcome the distrust brewed by Brexit and France’s traditionally independent approach to nuclear deterrence.   

Even while working to play a greater role in deterring Russia and assuring allies, Europe also wants to keep the United States engaged. Most U.S. officials still think the continent matters for advancing American interests. The aim should thus be to rebalance the transatlantic defense relationship so that Washington sees Europe as a capable strategic partner rather than as a dependent. The 2025 surge in defense spending and mass, readiness, and stockpile buildup helps signal that Europe is not a liability, but a pillar of Western security. 

Integrating new and emerging capabilities into joint planning and agreeing with their American counterparts on clear, consistent strategic messaging should be priorities for Europe. Without this alignment, mixed signals could inadvertently undermine deterrence efforts.

The past year has demonstrated that Europeans are working to strengthen the full range of their deterrent. For Moscow, the message is that aggression will be met with serious consequences; for European allies, that the UK and France are stepping up to play a larger nuclear role; and for Washington, that Europe is rebalancing the defense burden through serious conventional investment.  

And yet, heading into 2026, Europe still lacks a shared framework and a coherent epistemic community on deterrence. National debates remain fragmented, often contradictory, and shaped by different threat perceptions as well as levels of risk tolerance.

Europe needs practical habits of defense cooperation, including regular consultations, shared planning assumptions where possible, and greater clarity on escalation management and the nuclear–conventional interface. These discussions are ongoing between France, the UK, and Germany, but they must involve all allies, especially those on the front line. Only with shared principles can Europe effectively craft a coherent deterrence strategy calibrated to an array of audiences and suited to the strategic realities of the decade ahead.