Europe Needs an Enhanced Nuclear Deterrent (Whoever Occupies the White House)

For almost 80 years, the US has extended nuclear deterrence to its NATO Allies. But with Donald Trump back in the White House, European policymakers have become concerned about the reliability of the US nuclear umbrella. In parallel with their conventional rearmament, Europeans would be well advised to strengthen their nuclear capabilities too.

While America’s desire to disengage from European security is not new, there is little doubt that Trump has been the US president most sceptical of committing to collective defence through NATO. Even so, his administration’s core geopolitical ideas are broadly similar to those of the Obama and Biden administrations, which have seen Washington’s focus shift to the Indo-Pacific region over the past decade and a half. Approximately 375 000 US military personnel are now deployed in the Indo-Pacific, compared to 80 000 in Europe, while six of 11 carrier strike groups—America’s primary instrument of power projection—have home ports in the region. The imminent new National Defence Strategy and global force posture review are widely expected to further reduce US forces in Europe, with possible implications for the implementation of NATO’s regional defence plans.

Furthermore, experts assess that the US may no longer be able to fight two major wars in different theatres at the same time, a contingency the Pentagon prepared for throughout the Cold War. NATO Secretary General Mark Rutte has warned of a scenario in which Vladimir Putin and Xi Jinping could act in concert to destabilise or attack allied countries in order to overstretch the west.

Yet, especially among Republicans but also some Democrats, the idea of making Europeans responsible for their own conventional deterrence and defence has become increasingly popular. This concept, sometimes described as ‘dormant NATO’, envisions conventional defence responsibilities for Europe largely shifting to the European pillar of the Alliance with a limited US involvement through air defence and naval assets, while the US retains the role of providing nuclear deterrence for the continent.

Containing nuclear proliferation has been a central US foreign policy objective since the start of the atomic age. Washington has not only sought to prevent hostile states like Iran and North Korea from acquiring nuclear weapons but also close allies such as the UK and, more recently, Taiwan and South Korea. An arrangement whereby the US shifts conventional defence responsibilities to its partners while retaining a nuclear deterrence role may thus align with American interests—but it is more than questionable that it also serves the interests of Europeans.

Concepts and Political Realities

During the Cold War, West Berlin was home to 12 000 American, British, and French military personnel. Their presence conveyed the promise that any Warsaw Pact attack would compel a broader response from western capitals, potentially escalating a local situation to a global conflict and even a nuclear war. This dynamic was captured in Herman Kahn’s 44-step escalation ladder, which begins with political gestures and diplomatic posturing, moves through limited military actions and threats, and culminates in all-out thermonuclear conflict. Kahn emphasised that each step up the ladder increases risk and decreases manoeuvrability, substantially raising the stakes for an aggressor, but that not all steps are inevitable. The purpose of the ladder is not to encourage escalation but to control it, allowing states to signal resolve, threaten credibly, or de-escalate when necessary. Even though some may reject Kahn’s stringent conceptualisation of escalation, the risk of spiralling conflict is undeniable.

In the event of a US conventional disengagement from Europe, Kahn’s insights imply that US nuclear guarantees would also diminish in credibility: it is simply less likely that the US will jump into a conflict on a higher rung of the escalation ladder if it has not been deeply involved in the earlier stages, including through the loss of life. It could instead attempt to de-escalate the situation by pressuring the Europeans to make concessions on some of their core interests, as the Trump administration has done with Ukraine. Because the US has more leverage over most European countries than it does over Russia, such de-escalation efforts would likely be of disproportionate benefit to the Kremlin. The July 2025 trade deal between Washington and Brussels demonstrated that, partly due to a one-sided security dependence, the US is able to pressure Europe to swallow a bitter pill that fundamentally contradicts its interests.

Regarding Ukraine, at least in public, the US has refrained from nuclear signalling, emphasising de-escalation, while Russia has regularly engaged in belligerent rhetoric. France, by contrast, significantly ramped up its nuclear deterrence posture in early 2022, reportedly sending three of its four ballistic missile submarines to sea (normally, only one is on patrol) and conducting a planned missile test, while the US postponed two planned tests of its Minuteman intercontinental ballistic missile. This may indicate a gap in resolve among allies, or it may be that France has more freedom to operate as Russia fears its actions less than those of the US. Neither explanation should be welcome in Europe. Both raise the critical question of what happens if the US refuses any involvement in a future European crisis. Without a credible, Europe-based nuclear deterrent, the escalation ladder becomes less a tool of control and more a vulnerability. Without a tripwire, there may be no escalation path at all—just strategic paralysis.

Deterrence posture against a nuclear-armed Russia must be rock-solid. During the Cold War, if elements from either side had stepped across the Iron Curtain, a US-USSR clash would be almost inevitable. Today, the likely weakening presence of US armed forces in Europe requires the European nuclear powers, France and the UK, to step up. NATO’s 1974 Ottawa declaration acknowledged the complementary role that British and French nuclear forces play in the Alliance’s overall deterrence posture. Europe’s leaders must now give these forces greater visibility, including by more clearly projecting a nuclear umbrella over eastern Europe. They also need to make the necessary adjustments to doctrine and equipment, such as embracing the sub-strategic nuclear weapons required to discourage Russia from employing its own significant arsenal of tactical nuclear weapons.

Beyond Trump

The need for a Europeanised deterrent does not originate with Donald Trump but from broader structural shifts in the international system and long-term trends in US grand strategy. A future administration may be more transatlantic in rhetoric, but the underlying incentives that drive American retrenchment from Europe will remain. Europe can no longer afford to be a passive consumer of American security but must become a co-producer of deterrence: not in opposition to the US, but in recognition of the new reality that deterrence, including in the nuclear domain, must begin at home. To preserve peace, protect its interests, and play a meaningful role in global affairs, Europe will need to take its nuclear responsibilities more seriously, requiring in turn political courage, strategic vision, and difficult conversations within and between states.

A stronger conventional and nuclear-armed Europe might also encourage the US to remain invested in the continent’s security. In the 1960s, French General André Beaufre argued that a nuclear-armed France would oblige Washington to take his country’s vital interests seriously, effectively aligning the interests of both nations. Backing its ally would simply be the best option for the US to ensure that France could never find itself in a situation where it might use its nuclear weapons in defence of its fundamental interests. If European countries can build a framework in which they can credibly employ conventional and nuclear force self-sufficiently, the US will have an incentive to bolster them to ensure they never have to do so. To be strong in the future, the transatlantic relationship must find an alignment of interests today.

Views expressed in ICDS publications are those of the author(s).