Introduction
The expiry of New Strategic Arms Reduction Treaty (START) on 5 February 2026 removed the last legally binding cap on the strategic nuclear forces of the United States and Russia, the two states that still possess the overwhelming majority of the world’s nuclear weapons. With that legal endpoint, a half-century tradition of treaty-based predictability in the superpowers’ nuclear competition gave way to a looser, more politically contingent form of restraint: one in which any limits depend on unilateral decisions, informal understandings, and technical intelligence rather than enforceable obligations and routine verification.
Arms control treaties have historically served as infrastructure: they create red baselines, reduce worst-case assumptions, and provide mechanisms to prevent fear from driving procurement and escalation. When that infrastructure disappears, ‘nuclear risk’ becomes less visible but more embedded in ordinary political and economic life. Budget priorities shift; alliance debates sharpen; crisis signalling becomes harder to interpret; and the line between conventional and nuclear capabilities blur in ways that can compress decision time during shocks. In this environment, the public does not experience nuclear danger as a single event. Instead, it is lived as a pattern of costs, anxieties, and strategic choices, especially in the most exposed theatres in Europe and Asia.
