Deterrence has long been a cornerstone of interaction among states. This was especially true when state interests clashed and when political leaders sought to avoid direct military conflict. In traditional deterrence relationships, calculations of military, economic, and diplomatic power determined the degrees of deterrence effectiveness. This seemed to change with the advent of the Cold War. The potential destructiveness of nuclear weapons combined with the relatively small numbers of states that possessed them suggested a need for new concepts of deterrence tailored to govern the nuclear...