| The premise of this dissertation is straight-forward---the U.S., as hegemon, acts unilaterally given the power disparity between it and the rest of the world. In solving the puzzle of why presidents make the "wrong" decision to act alone, I organize international conflict literature along traditional lines---international and domestic explanations---and use Gilpin's (1981) hegemonic stability theory to test a theory of unilateral use of force decision making. In order to overcome a lack of scientific study on unilateralism, I devise a definition and coding rules for unilateral use of force, develop a sequential model of presidential use of force decision making, and construct a new, alternative measure of military power, a Composite Indicator of Military Revolutions (CIMR). I then use three methods---a statistical test with a heckman probit model, an experiment, and case studies---to test U.S. crisis behavior since 1937. I find that presidents are realists and make an expected utility calculation to act unilaterally or multilaterally after their decision to use force. The unilateral decision, in particular, positively correlates with a wide military gap vis-a-vis an opponent, an opponent located in the Western hemisphere, and a national security threat. |
