This chapter offers a theoretically informed overview of American foreign policy during the Cold War. It covers the main historical developments in U.S. policy: from the breakdown of the wartime alliance with the USSR and the emergence of the US–Soviet diplomatic hostility and geopolitical confrontation,to U.S. military interventions in the third world and the U.S. role in the ending of the Cold War. The chapter begins with a discussion of three main theoretical approaches to American foreign policy during the Cold War: realism, ideational approaches, and socio-economic approaches. It then considers the origins of the Cold War and containment of the Soviet Union, focusing on the Truman Doctrine and the Marshall Plan. It also examines the militarization of U.S. foreign policy with reference to the Korean War, Cold War in the third world, and the role of American foreign policy in the ending of the Cold War.