Containment was a United States policy using numerous strategies to prevent the spread of communism abroad. A component of the Cold War, this policy was a response to a series of moves by the Soviet Union to enlarge communist influence in Eastern Europe, China, Korea, and Vietnam. It represented a middle-ground position between détente and rollback. The basis of the doctrine was articulated in a 1946 cable by U.S. diplomat George F. Kennan. As a description of U.S. foreign policy, the word originated in a report Kennan submitted to U.S. Defense Secretary James Forrestal in 1947, a report that was later used in a magazine article. It is a translation of the French cordon sanitaire, used to describe Western policy toward the Soviet Union in the 1920s.

The word containment is associated most strongly with the policies of U.S. President Harry Truman (1945–53), including the establishment of the North Atlantic Treaty Organization (NATO), a mutual defense pact. Although President Dwight Eisenhower (1953–61) toyed with the rival doctrine of rollback, he refused to intervene in the Hungarian Uprising of 1956. President Lyndon Johnson (1963–69) cited containment as a justification for his policies in Vietnam. President Richard Nixon (1969–74), working with his top advisor Henry Kissinger, rejected containment in favor of friendly relations with the Soviet Union and China; this détente, or relaxation of tensions, involved expanded trade and cultural contacts. President Jimmy Carter (1976–81) emphasized human rights rather than anti-communism, but dropped détente and returned to containment when the Soviets invaded Afghanistan in 1979. President Ronald Reagan (1981–89), denouncing the Soviet state as an "evil empire", escalated the Cold War and promoted rollback in Nicaragua and Afghanistan. Central programs begun under containment, including NATO and nuclear deterrence, remained in effect even after the end of the war.