This chapter explores the relationship between American military power and foreign policy. It also considers important debates regarding containment, deterrence, preemption, and the limits of military power. The chapter begins with a discussion of the rise of American military power during the period 1945–91, focusing on the military implications of containment and deterrence as well as the role of deterrence in ending the arms race. It then examines the fundamental questions that the United States had to confront in the post-Cold War era regarding its role in the world and its military power; for example, whether nuclear weapons are still useful, and for what purpose the U.S. military should be deployed. The chapter concludes with an analysis of the U.S. response to terrorism, with particular emphasis on the U.S. involvement in the war in Afghanistan (2001) and the war in Iraq (2003).