Pearl Harbor: Deterrence Theory and Decision Theory

According to most analyses, Japan's decision to attack the United States at Pearl Harbor in 1941 can only be explained as an act of irrationality, given the difference in relative power of the two nations. This article contends that for most purposes of analyzing national decision-making the rationality-irrationality distinction is not useful, and sug gests instead a detailed analysis of certain components of the decision and of the alterna tives considered. The Japanese decision must be seen in the context of their possible attack on third parties, notably the British and Dutch colonies in the Southwest Pacific, and the deterrent threat posed by some probability that the United States would resist the attack even though its own territory was not directly involved. A general decision- theory model was developed and tested on 17 cases in the earlier work of the author. It considers the utility to the decision-makers of each of three possible courses of action: no attack at all (retain the status quo), attack third party only, and attack also the major power which poses the deterrent threat to protect the third party. The utilities must be weighted by the probabilities attached by the decision-makers to the achievement of each out come. In this case the Japanese government attached strongly negative utilities to the status quo. Furthermore, though it would have greatly valued an unresisted attack on the European colonies, it considered it very unlikely that the United States would fail to respond militarily. It reached this assessment on the basis of extensive military, political, and economic ties between the United States and the Southwest Pacific area, despite the absence of an overt alliance. Hence, by comparison, attacking the United States directly had some attractions, given the vulnerability of the Pearl Harbor fleet and certain (mistaken) assumptions about United States willingness to conduct a long war.