By: History.com Editors
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Published: November 09, 2009
Last Updated: March 06, 2025
The domino theory was a Cold War policy that suggested a communist government in one nation would quickly lead to communist takeovers in neighboring states, each falling like a row of dominos. In Southeast Asia, the U.S. government used the now-discredited domino theory to justify its involvement in the Vietnam War and its support for a non-communist dictator in South Vietnam. In fact, the American failure to prevent a communist victory in Vietnam had much less of an impact than had been assumed by proponents of the domino theory. With the exception of Laos and Cambodia, communism failed to spread throughout Southeast Asia.
In September 1945, the Vietnamese nationalist leader Ho Chi Minh proclaimed Vietnam’s independence from France, beginning a war that pitted Ho’s communist-led Viet Minh regime in Hanoi (North Vietnam) against a French-backed regime in Saigon (South Vietnam).
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Under President Harry Truman, the U.S. government provided covert military and financial aid to the French; the rationale was that a communist victory in Indochina would precipitate the spread of communism throughout Southeast Asia. Using this same logic, Truman would also give aid to Greece and Turkey during the late 1940s to help contain communism in Europe and the Middle East.
By 1950, U.S. foreign policy officials had firmly embraced the idea that the fall of Indochina to communism would lead rapidly to the collapse of other nations in Southeast Asia. The National Security Council included the theory in a 1952 report on Indochina, and in April 1954, during the decisive battle between Viet Minh and French forces at Dien Bien Phu, President Dwight D. Eisenhower articulated it as the “falling domino” principle:
“You have a row of dominoes set up, you knock over the first one, and what will happen to the last one is the certainty that it will go over very quickly,” Eisenhower said. “So you could have a beginning of a disintegration that would have the most profound influences.”
In Eisenhower’s view, the loss of Vietnam to communist control would lead to similar communist victories in neighboring countries in Southeast Asia (including Laos, Cambodia and Thailand) and elsewhere (India, Japan, the Philippines, Indonesia, and even Australia and New Zealand). “The possible consequences of the loss [of Indochina],” Eisenhower said, “are just incalculable to the free world.”
After Eisenhower’s speech, the phrase “domino theory” began to be used as a shorthand expression of the strategic importance of South Vietnam to the United States, as well as the need to contain the spread of communism throughout the world.
North Vietnam's surprise attack on the South during the holiday of Tet altered the entire course of the Vietnam War. Morale among U.S. and South Vietnamese troops was crushed, and Americans back home increasingly wondered why their soldiers were there in the first place.
After the Geneva Conference ended the French-Viet Minh war and split Vietnam along the latitude known as the 17th parallel, the United States spearheaded the organization of the Southeast Asia Treaty Organization (SEATO), a loose alliance of nations committed to taking action against “security threats” in the region.
John F. Kennedy, Eisenhower’s successor in the White House, would increase the commitment of U.S. resources in support of the Ngo Dinh Diem regime in South Vietnam and of non-communist forces fighting a civil war in Laos in 1961-62. In 1963, after serious domestic opposition to Diem arose, Kennedy backed away from support of Diem himself but publicly reaffirmed belief in the domino theory and the importance of containing communism in Southeast Asia.
Three weeks after Diem was murdered in a military coup in early November 1963, Kennedy was assassinated in Dallas; his successor Lyndon B. Johnson would continue to use the domino theory to justify the escalation of the U.S. military presence in Vietnam from a few thousand soldiers to more than 500,000 over the next five years.
The domino theory is now largely discredited, having failed to take into account the character of the North Vietnamese and Viet Cong struggle in the Vietnam War.
By assuming Ho Chi Minh was a pawn of the communist giants Soviet Union and China, American policymakers failed to see that the actual goal of Ho and his supporters was Vietnamese independence, not the spread of communism.
In the end, even though the American effort to block a communist takeover failed, and North Vietnamese forces marched into Saigon in 1975, communism did not spread throughout the rest of Southeast Asia. With the exception of Laos and Cambodia, the nations of the region remained out of communist control.
Domino Theory. ScienceDirect.
Foreign Relations of the United States, 1952–1954, Indochina, Volume XIII, Part 1: Editorial Note. U.S. Department of State, Office of the Historian.
World War II, Race, and the Southeast Asian Origins of the Domino Theory. Wilson Center.
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