For decades, bilateral treaties between the U.S. and Russia, together with international instruments, formed the backbone of the international nuclear security regime. This architecture was a mix of legally binding limits on their nuclear weaponry and multilateral agreements on non-proliferation and disarmament, especially under the Non-Proliferation Treaty. Through the imposition of limits, verification mechanisms and institutional dialogue, this system increased strategic predictability and reduced the risk of unrestrained nuclear escalation between major powers. During the last two decades, however, this framework has largely disappeared, with the most recent landmark being the expiry of the New START Treaty on 5 February 2026. This means that, for the first time since the early 1970s, there are no longer any binding restrictions on the strategic nuclear arsenals of the two largest nuclear-weapon states. Rather than an isolated development, this marks a broader erosion of the post-Cold War arms control framework (Woolf, 2023). At the same time, the non-proliferation regime is also under pressure, partly due to frustration over the lack of progress on disarmament and the establishment of the Treaty on the Prohibition of Nuclear Weapons (TPNW), which has highlighted normative tensions within Europe (Meyer & Sauer, 2023).
This paper argues that these developments reflect a structural shift toward uncertainty in the international nuclear order rather than a temporary treaty crisis. These developments are of direct significance to Europe. Geographically and politically, the continent is located in close proximity to nuclear superpowers and for decades, it was one of the primary beneficiaries of the relative stability that nuclear arms control brought. The erosion of these mechanisms raises some fundamental questions about strategic stability, crisis management and Europe’s position in an increasingly competitive and multipolar nuclear environment. This paper, therefore, analyses the erosion of the nuclear arms control framework in recent years and assesses its implications for Europe’s strategic environment in an increasingly multipolar nuclear order.
About the author
Leen Leclerq is currently a research intern at the Flemish Peace Institute and was previously a research trainee at Finabel.