The United States and the world face serious threats to nuclear stability and peace, now and in the coming decades. Within the nuclear arena, U.S. policy makers will need to make strategic decisions related to nuclear risks to assist with long-term planning as well as responding in real time to unanticipated events. The occurrence of unanticipated nuclear events is expected to increase as more countries develop, expand, or field nuclear energy capability; more countries consider development of nuclear weapon capability and new nuclear weapon states emerge; and nuclear weapon states expand their nuclear arsenals.

At the request of the Department of Defense, the National Academies of Sciences, Engineering, and Medicine established and managed the Committee on Risk Analysis Methods for Nuclear War and Nuclear Terrorism to explore U.S. government methods for assessing nuclear war and nuclear terrorism risks and how those assessments are used to develop strategy and policy. This publication is the unclassified Phase 2 version of the final classified report. Risk Analysis Methods for Nuclear War and Nuclear Terrorism: Phase II builds on an earlier Phase I unclassified report. This book expands upon the use of analytical methods to assess the risks of nuclear terrorism and nuclear war and the role such approaches may play in U.S. security strategy.