The Bureau of International Security and Nonproliferation (ISN) prevents and rolls back the spread of WMD, delivery systems, and advanced conventional weapons capabilities; protects U.S. critical and emerging technology; and promotes the peaceful uses of nuclear energy, science, and technology. In close collaboration with other bureaus within the State Department, other U.S. agencies, and a diverse range of international and non-governmental partners, ISN further tracks, develops, and implements effective policy responses to proliferation threats and shapes the international security environment to prevent their recurrence.