The New Strategic Arms Reduction Treaty (New START) expired at midnight on Thursday, February 5, 2026, marking the first time in more than five decades that no legally binding limits constrain the strategic nuclear arsenals of the United States and Russia, the world’s two largest nuclear powers possessing the overwhelming majority of global nuclear weapons.
The treaty’s expiration ends more than 50 years of bilateral arms control agreements that helped reduce global nuclear arsenals by over 80 percent since the Cold War’s peak and provided unprecedented verification measures enabling both countries to make security decisions based on real information rather than speculation, according to the Center for Arms Control and Non-Proliferation.
United Nations Secretary General António Guterres characterized the expiration as a grave moment for international peace and security, stating that strategic arms control between the United States and Russia throughout the Cold War and its aftermath helped prevent catastrophe, built stability, prevented devastating miscalculation, and facilitated the reduction of thousands of nuclear weapons from national arsenals.
New START, signed in Prague on April 8, 2010, by Presidents Barack Obama and Dmitry Medvedev and entering force on February 5, 2011, limited each country to 1,550 deployed strategic nuclear warheads on 700 deployed delivery systems including intercontinental ballistic missiles, submarine launched missiles, and bombers. The treaty established comprehensive verification provisions including twice yearly data exchanges, mutual notifications about strategic force movements, and short notice on site inspections.
The treaty was extended for five years in February 2021 during the Biden administration, representing the only extension permitted under treaty provisions. New START could not be extended beyond Wednesday without formal re-ratification requiring a two-thirds majority in the United States Senate, a prospect experts consider unlikely given current political dynamics.
Russian President Vladimir Putin proposed in September 2025 that both countries continue observing New START’s numerical limits for one year beyond expiration, with the possibility of extension. President Donald Trump initially reacted positively to the proposal, stating it sounded like a good idea, though no formal agreement materialized before the treaty’s expiration.
Verification provisions ceased functioning well before the treaty expired. Both countries suspended on site inspections in 2020 due to the COVID-19 pandemic. Russia announced suspension of its treaty participation in February 2023 citing hostile United States actions, support for Ukraine, and the need to account for the nuclear potential of Britain and France, though Moscow stated it would continue respecting quantitative restrictions.
The United States subsequently stopped sharing certain information with Russia required by New START, though open source estimates indicate both countries maintained the treaty’s numerical limits through the expiration date. The breakdown in verification mechanisms means neither country possesses the transparency and insight into the other’s nuclear deployments that existed throughout most of the past half century.
John Erath, Senior Policy Director at the Center for Arms Control and Non-Proliferation and a 30 year State Department veteran who served on the National Security Council, stated that while officials knew New START would end for 15 years, no one showed the necessary leadership to prepare for its expiration. He emphasized that the treaty’s value extended beyond limiting nuclear weapons numbers to providing unprecedented insights enabling informed decision making.
The expiration comes weeks before the April and May 2026 Review Conference of the Nuclear Non-Proliferation Treaty (NPT) in New York, where nuclear weapon states must explain implementation progress over the past five years and outline future commitments. The treaty’s demise without a successor agreement potentially signals that instead of showing restraint and demonstrating disarmament progress, nuclear armed states are moving in the opposite direction, potentially deepening divisions between nuclear and non nuclear states.
Experts warn the expiration creates conditions for a renewed nuclear arms race, though analysts note competitive contours among Chinese, Russian, and United States nuclear programs are already established. China’s ongoing force expansion represents the dominant factor in post New START nuclear competition, with projections suggesting a decade long buildup rather than immediate dramatic increases.
The United States Strategic Posture Commission described American nuclear programs as necessary but not sufficient to deter potential adversaries. Senior National Security Council officials indicated the United States may need to increase deployed warhead numbers in coming years absent changes in adversary arsenal trajectories, with Pentagon officials confirming exploration of options to increase future launcher capacity and deployed warheads across land, sea, and air based systems.
Hendrik de Bruin, Head of Security Consulting for Africa at Check Point Software Technologies, noted that while nuclear arms control negotiations primarily involve major powers, the consequences of treaty collapse affect global security. The absence of verification measures and numerical limits increases uncertainty, potentially elevating nuclear miscalculation risks during periods of heightened international tensions.
Arms control advocates emphasize that New START’s expiration does not eliminate legal obligations under the Nuclear Non-Proliferation Treaty requiring nuclear weapon states to negotiate disarmament and end the arms race. Multiple confidence building measures from previous treaties remain available for potential adoption, and informal arrangements to observe expired treaty limits have historical precedent, including the 1981 agreement to abide by the unratified SALT II Treaty while negotiating START I.
