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The Vietnam War (1945–1975)

History SparkNotes

U.S. Involvement and the Cold War Context: 1947–1955

Vietnamese Nationalism and the First Indochina War: 1900–1954

Diem and the Republic of Vietnam: 1955–1960

1947 Containment doctrine begins to influence U.S. foreign policy
1948 USSR blockades Berlin; United States responds with Berlin airlift
1949 USSR conducts first successful atomic bomb test China falls to Communist rebels under Mao Zedong
1954 Eisenhower articulates domino theory
1955 U.S.-backed Ngo Dinh Diem ousts Bao Dai from power in South Vietnam
Key People
George F. Kennan -  U.S. State Department analyst who developed influential policy of containment in 1947
Harry S Truman -  33rd U.S. president; adopted containment as a major part of U.S. foreign policy
Dwight D. Eisenhower -  34th U.S. president; modified containment policy with more pessimistic domino theory
Ngo Dinh Diem -  U.S.–backed leader of South Vietnam; took power in fraudulent elections in 1955
Edward Lansdale -  CIA operative stationed in Vietnam in 1954; eventually became advisor to Diem

Origins of the Cold War

U.S. involvement in Vietnam occurred within and because of the larger context of the Cold War between the United States and the Soviet Union. Immediately after World War II, tensions between the United States and USSR escalated, as Soviet forces occupied nearly all of Eastern Europe and set up Communist governments there as a buffer between the Soviet Union and the capitalist West. In 1946, British prime minister Winston Churchill famously railed against the USSR in his “iron curtain” speech, which lamented the sudden wall of secrecy that had gone up between Eastern and Western Europe.


In 1947, U.S. State Department analyst George F. Kennan argued that the USSR was not likely to make any rash moves and that the United States could keep Communism from spreading simply by deterring Soviet expansion at critical points, mostly in Europe, over the long term. This policy of containment became extraordinarily influential in the U.S. government and became the basis of U.S. policy for much of the Cold War.

Escalation and Paranoia

Three major events in 1948 and 1949 brought the American fear of Communism to a fever pitch. First, the USSR, which controlled East Germany, attempted to drive U.S., British, and French forces out of West Berlin by cutting off all outside access to the city. The United States responded to this blockade with the Berlin airlift over the winter of 19481949, dropping crucial supplies into West Berlin until the Soviet Union relented. Then, in August 1949, the USSR successfully tested its first atomic bomb. Finally, in October 1949, after years of civil war, the Nationalist government of China fell to the Communist forces of Mao Zedong. The combined force of these three events plunged the United States into a deep paranoia and fear that Communists would take over the world and might even be plotting secret operations in the United States.


In this environment of alarm, national security advisors of U.S. president Harry S Truman wrote an influential memo called NSC-68 , which advocated a tremendous increase in military spending to finance a massive military buildup, hoping to deter Soviet aggression. Following the policy outlined by this document, the United States became increasingly concerned with Communist expansion anywhere, not just at the critical points that Kennan had identified. Combined with the beginning of the Korean War in 1950, NSC-68 encouraged President Truman to begin a rapid buildup of the U.S. military.

The Domino Theory

After the fall of Dien Bien Phu in 1954, Truman’s successor, President Dwight D. Eisenhower, gave a speech that would soon become famous and important as an outline of U.S. Cold War policy. In the speech, Eisenhower drew on Kennan’s previously articulated containment policy but went a step further in describing what became known as the domino theory. Eisenhower stated that the United States needed not only to contain the USSR at critical locations but in all locations, for if one nation became Communist, its neighbors were likely to turn Communist as well, falling like a row of dominoes.

As a result of the domino theory, U.S. policy makers began to see Vietnam as extremely important. If Vietnam became Communist, domino-theory logic held that all of Indochina, and perhaps even all of Southeast Asia, might become Communist. Well aware of the popularity of Ho Chi Minh and his Viet Minh associates in both North and South Vietnam, U.S. leaders feared that the free elections promised at the Geneva Conference, which were scheduled to occur in 1956, would result in a unified, Communist Vietnam.

Ngo Dinh Diem

Committed to the logic of the domino theory, U.S. leaders sought to forestall the elections in Vietnam. The United States thus threw its support behind the politician Ngo Dinh Diem, a Vietnamese nationalist and Catholic who emphasized Confucian values of loyalty and tradition and opposed the overthrow of old Vietnamese social structures—a move that the revolutionary Vietnamese Communists advocated.

The Republic of Vietnam

In 1955, with U.S. support, Diem rejected the prospect of Vietnam-wide elections as specified by the Geneva Accords and instead held a referendum limited to the southern half of the country. Using fraud and intimidation, Diem won over 98 percent of the vote, removed the feeble Bao Dai from power, and proclaimed South Vietnam to be the Republic of Vietnam (RVN). A CIA operative working in Saigon, Edward Lansdale, was installed as an advisor to Diem. The United States then helped Diem organize the Army of the Republic of Vietnam (ARVN) to control his new state.

Assessing U.S. Involvement

The United States’ involvement in Vietnam can be understood only within the context of the larger Cold War against the Soviet Union. After formulating the policy of containment and the domino theory in a response to the USSR, the United States would become more and more involved in checking Communism’s spread in Vietnam. Americans and others around the world had watched as Britain and France appeased Adolf Hitler and the expansionist Nazi Germany prior to World War II—an approach that had quickly brought disaster. As a result, rather than appease the USSR, the United States vowed to stop aggression before it happened. Whether or not this new tactic would work, or was even appropriate, was not yet clear. Policy makers today claim to have learned the “lessons of Vietnam,” but the American tragedy in Vietnam was itself largely built on “lessons of World War II.”

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