Cold War: A period of political tension and rivalry between the United States (capitalism) and the Soviet Union (communism) that indirectly fueled the spread of communism.
Iron Curtain: Refers to the metaphorical division between Eastern Europe (under Soviet influence) and Western Europe during the Cold War, which restricted the spread of non-communist ideas.
Vietnam War: A conflict that occurred from 1955 to 1975 in Vietnam, during which communist forces fought against anti-communist forces supported by the United States. The war furthered the spread of communism in Southeast Asia.