What was containment in the Cold War?

Containment in the Cold War was the central foreign policy strategy of the United States to prevent the spread of communism and Soviet influence beyond where it already existed after World War II, rather than trying to roll it back directly. The concept was first articulated in 1946 by American diplomat George F. Kennan in his famous Long Telegram and X Article, where he argued that Soviet communism was ideologically driven to expand and must be contained by firm and vigilant resistance. It became official US policy under President Harry Truman with the Truman Doctrine in 1947, which stated the US would support free peoples resisting subjugation. Containment shaped decades of US actions, including the Marshall Plan that provided 13 billion dollars to rebuild Western Europe to make it economically resistant to communism, the creation of NATO in 1949 as a military alliance to contain Soviet power in Europe, intervention in the Korean War to stop North Korea from taking over South Korea, the Vietnam War to prevent communist takeover of South Vietnam, and the Cuban Missile Crisis response to contain Soviet missiles. Containment did not mean direct war with the USSR, but rather proxy wars, economic aid, espionage, nuclear deterrence, and diplomacy to keep communism boxed in. It remained US strategy until the Soviet Union collapsed in 1991.