For too long, nuclear deterrence theory has been treated as a casualty of the end of the Cold War. During the preceding period of superpower rivalry, debates over the credibility of nuclear deterrence attracted the attention of sophisticated game theorists in diverse disciplines. But with the end of the Cold War, this research tradition virtually ground to a halt. In this important new book, two long-term contributors to this body of research revisit these issues and effectively recast these models as representations of policy dilemmas of long-standing and continuing relevance. For instance, their models of U.S. strategic doctrines of massive retaliation and flexible response prove relevant to any situation in which the parties perceive two levels of conflict to be significantly different, even if neither level involves the use of nuclear weapons.