For realists, in the absence of effective collective security sanctions against transgressors, except what individual states themselves mete out, the "rational" policy is to pursue national interest without care to the costs that might be incurred by others, and to maximize one's chances of achieving ends in the face of opposition through the pursuit of power. Collective production of goods (such as security) is therefore unlikely, and states must rely on "self-help" rather than allies or international organizations to define and defend their national interests. This would appear to be the underlying rationality of the supposed unilateralism of current U.S. foreign policy, and the foundation of the threat of renewed war on the Korean peninsula. However, the past hundred years have seen increasing levels of inter-governmental cooperation and collective action. States do not consistently seek to destroy or subdue each other, but rather most of them, most of the time, including even the most powerful and independent actors, demonstrate a rationality indicative of international societal constraints, and are conspicuously law-abiding. Thus, even in the context of a wider "War on Terror," U.S. decision-making regarding North Korea is still likely to reflect the concerns of allies, enemies, and internal and external constituencies, rather than purely being the product of a rational cost-benefit analysis of a hierarchy of preferred outcomes. This paper will explain why, in realist terms, states and their leaders appear to be acting so irrationally.