How do states use nuclear weapons to achieve their foreign policy goals? This presentation, drawn from an ongoing book project, argues that states use nuclear weapons to facilitate a wider range of foreign policy behaviors than scholars have previously understood. It shows that states understand these benefits and change their foreign policies accordingly when they acquire them. In making this argument, the book makes three contributions. First, it offers a novel typology of foreign policy behaviors for understanding the impact of nuclear weapons on foreign policy. Second, it offers a theory, “nuclear opportunism,” that makes predictions for how a state’s foreign policy will change when it acquires nuclear weapons that is in contrast to the dominant “theory of the nuclear revolution”. Third, it uses detailed historical evidence drawn from multi-archival research to test the theory against three cases—the United Kingdom, South Africa, and the United States, before using the theory to make predictions for how other states might behave if they acquired nuclear weapons.