In this interview, Matthew Bunn, the Schlesinger professor of the practice of energy, national security and foreign policy at Harvard Kennedy School, discusses the evolution of United States nuclear policy. Bunn observes that “Evolving and disruptive technologies may affect the risk that nuclear weapons would actually be used,” and suggests that they are likely to play a crucial role in shaping nuclear policy and international security. The New START Treaty, signed in 2010 and expiring in February 2026, is the last major arms control agreement between the United States and Russia limiting nuclear arsenals. The NPT, for instance, aims to prevent the spread of nuclear weapons, while the CTBT seeks to ban nuclear testing—but has not been ratified by the United States. The collapse of New START would leave a significant gap in controlling nuclear arms, Bunn explains, heightening the risk of nuclear conflict.