Nuclear Deterrence in Shifting Euro-Atlantic Security Architecture

Nuclear deterrence remains a fundamental component of NATO’s defence posture. As the Alliance and its members continue to stress, 'As long as nuclear weapons exist, it [NATO] will remain a nuclear Alliance'. In the face of monumental challenges to NATO and the broader established Euro-Atlantic security architecture, from within the Alliance and outside it, how will these shifts have an impact on the role of nuclear deterrence in Euro-Atlantic security dynamics?

This paper examines how key challenges to the existing Euro-Atlantic security architecture impact nuclear deterrence in Europe, and outlines priorities for strengthening nuclear deterrence in support of European security. It argues that credible nuclear deterrence in Europe continues to depend on US conventional and nuclear backstops but that efforts on the part of both nuclear and non-nuclear European NATO Allies can help strengthen the effectiveness of nuclear deterrence in Europe, even as US commitments to European security come under doubt. Strengthening nuclear deterrence in Europe should focus on prioritising efforts towards complicating Russian nuclear and broader strategic decision-making and disabusing Moscow of any beliefs that it will be able to manage escalation dynamics should it pursue a limited incursion into NATO territory or limited nuclear strikes against European NATO Allies. This will require improving the distribution of deterrence responsibilities across nuclear and non-nuclear NATO Allies through the bolstering of conventional capabilities (critically, by non-nuclear NATO Allies), improving conventional-nuclear integration in NATO deterrence thinking, and considering options for more flexible UK and French nuclear capabilities in the long term.

Methodology

This paper is part of a RUSI project on the future of Euro-Atlantic security architecture, supported by the UK’s Foreign, Commonwealth & Development Office. The analysis draws partly on the outcomes of a roundtable discussion on the role of nuclear weapons in Euro-Atlantic security, hosted by RUSI in Brussels in October 2025 and attended by non-governmental experts and officials from NATO member states. The conversation was held on a non-attribution basis; however, those participants who granted permission for attribution are named at the end of the paper. The themes that emerged in the workshop discussion have been supplemented by a review of US, British, French, other European and Russian primary sources and secondary analysis, as well as further discussions with experts in European nuclear and conventional dynamics. This paper aims to serve as a contribution to existing work in this space, highlighting key factors that need to be considered in future debates on the state and future of nuclear deterrence in Euro-Atlantic security dynamics. The paper is not a definitive and comprehensive analysis of the role of nuclear weapons in future Euro-Atlantic security dynamics, in part due to the limited scope and timeline of the research process, as well as the broad scope of the subject matter.

Nuclear Deterrence in Europe: Challenges and Limits

Broad challenges to European security and its underlying architecture have been introduced in the first paper published as part of the RUSI Future Euro-Atlantic Security Architecture research project. These challenges include the persistent threat of Russian aggression, US disengagement from the region, growing Chinese assertiveness, and intra-European and national political shifts. This paper examines the first three of these challenges – Russian aggression, US disengagement and a growing threat perception with regard to China – in greater detail and in the context of their relevance to nuclear deterrence dynamics in Europe. This section also considers the current state and limits of the UK and French nuclear deterrents.

Russian Aggression and Asymmetries in Capabilities

Russia will remain the primary threat to European security and the primary focus of European defence and nuclear deterrence planning in the short to medium terms. This comes across clearly in the UK’s 2025 Strategic Defence Review (SDR), the 2025 update of France’s Revue nationale stratégique 2025 (NSR), as well as NATO’s 2022 Strategic Concept. The SDR makes repeated references to the ‘enduring threat’ that Russia poses to UK and European security across multiple domains – including, space, cyberspace, information operations, undersea warfare, and chemical and biological weapons – and identifies ‘Russia's increasing reliance on nuclear coercion … [as] the central challenge for the UK and its NATO Allies in the coming decades’. The 2025 update of the French NSR stresses that ‘by 2030, the main threat to France and Europeans is the risk of open warfare against the heart of Europe’, linking the ‘particularly high risk of a major high-intensity war in Europe’ to the threat posed by Russia. NATO’s 2022 Strategic Concept points to similar risks, identifying Russia as ‘the most significant and direct threat to Allies’ security and to peace and stability in the Euro-Atlantic area’ and noting that it ‘cannot discount the possibility of an attack against Allies’ sovereignty and territorial integrity’.

In particular, Western policymakers and analysts have expressed concerns over the threat of potential Russian ground incursions into NATO territory. While some experts have – rightly – warned against over-estimating the likelihood of such an eventuality, the warnings of potential ‘high-intensity war in Europe’ referenced above suggest that it is a scenario that Europe is considering and preparing to deter or defend against.

While NATO maintains considerable conventional superiority over Russia, Russia benefits from quantitative advantages over Europe in personnel and ground forces and is learning lessons from the war in Ukraine to further strengthen its ground forces. Europe also suffers from shortages in long-range fires when compared to Russia’s long-range strike capabilities, which include an expansive and diversified arsenal of cruise and ballistic missiles and an ability to produce and field large quantities of relatively inexpensive and expendable UAVs. European inferiority in conventional capabilities on land is currently offset by superior NATO airpower, expected to be able to defeat Russian Integrated Air and Missile Defence (IAMD), upon which Moscow would rely to provide cover for its land forces during a ground incursion. However, critical aspects of NATO’s IAMD and SEAD/DEAD (suppression and destruction of enemy air defence) capabilities are critically dependent on US systems and enablers.