Exploring the Nuclear Posture Implications of Extended Deterrence and Assurance

The emerging North Korean and Iranian nuclear capabilities, coupled with ongoing Chinese and Russian strategic modernization programs, have brought increased attention from both practitioners and strategists to U.S. extended nuclear deterrence and the role it plays in assuring allies that the United States is committed to protecting their security. As one element of its consideration of extended deterrence and assurance, the Office of the Secretary of Defense for Policy contracted a CSIS study team, led by Clark Murdock and Jessica Yeats, to examine the implications of extended deterrence in the post-9/11 era for the United States nuclear posture. 

The purpose of the report is to identify the characteristics of the U.S. nuclear force posture that support extended deterrence and analyze how changes in the force posture affect the credibility of its assurance, paying particular attention to the competing needs and interests of U.S. allies in Europe, Northeast Asia and the Middle East.

The credibility of deterrence and assurance depends on a spectrum of factors affecting U.S. intent and capability as perceived by three critical audiences: the potential aggressor, the state under the umbrella, and the American public. By analyzing the differences with which each audience perceives and interprets U.S. force posture, the report demonstrates that the nuclear posture implications of extended deterrence and assurance are additive and cumulative, despite some fungibility between them.

The report begins by addressing extended deterrence and assurance at the conceptual level. Chapters III and IV then analyze how these factors affect the requirements, broadly defined, for extended deterrence and assurance, respectively. The analysis of both relationships is then re-integrated in the regional chapters (Europe, Northeast Asia and the Middle East) and a final chapter on longer-term trends and challenges.