The Domino Theory
Explore the domino theory — the Cold War belief that if one country fell to communism, its neighbors would follow, used to justify American interventions worldwide.
The domino theory was the geopolitical idea that if one country fell to communism, neighboring countries would follow in succession, like a row of falling dominoes. First articulated by President Eisenhower in 1954 regarding Southeast Asia, the theory became a cornerstone of American Cold War foreign policy and the primary justification for military interventions from Korea to Vietnam to Latin America.
The theory had some historical basis: communist governments had indeed spread across Eastern Europe after World War II, China fell to communism in 1949, and communist insurgencies were active across Southeast Asia. American policymakers feared that the loss of any country to communism would encourage revolutionary movements elsewhere and undermine confidence in American alliances.
The domino theory drove some of the Cold War's most consequential — and controversial — decisions. It justified American involvement in Vietnam, which cost 58,000 American and millions of Vietnamese lives. It rationalized support for authoritarian regimes that were anti-communist, from South Korea to Chile. After Vietnam fell to communism in 1975 without triggering the predicted regional collapse, the theory was largely discredited. But its logic — that threats must be contained early before they spread — continues to influence foreign policy debates.