Why Did the US Enter the Vietnam War?

Vietnam War
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The U.S. entered the Vietnam War in an attempt to prevent the spread of communism, but foreign policy, economic interests, national fears, and geopolitical strategies also played major roles. Learn why a country that had been barely known to most Americans came to define an era.

Key Takeaways: U.S. Involvement in Vietnam

  • The Domino Theory held that communism would spread if Vietnam became communist.
  • Anti-communist sentiment at home influenced foreign policy views.
  • The Gulf of Tonkin incident appeared to be a provocation for war.
  • As war continued, desire to find an "honorable peace" was motivation to keep troops in Vietnam.

The Domino Theory

Beginning in the mid-1950s, the American foreign policy establishment tended to view the situation in Southeast Asia in terms of the Domino Theory. The basic principle was that if French Indochina (Vietnam was still a French colony) fell to the communist insurgency, which had been battling the French, the expansion of communism throughout Asia would be likely to continue unchecked.

Taken to its extreme, the Domino Theory suggested that other nations throughout Asia would become satellites of either the Soviet Union or Communist China, much like nations in Eastern Europe had come under Soviet domination.

President Dwight Eisenhower invoked the Domino Theory in a press conference held in Washington on April 7, 1954. His reference to Southeast Asia becoming communist was major news the following day. The New York Times headlined a page one story about his press conference, “President Warns of Chain Disaster if Indo-China Goes.”

Given Eisenhower’s credibility on military matters, his prominent endorsement of the Domino Theory placed it at the forefront of how many Americans for years would view the unfolding situation in Southeast Asia.

Political Reasons: Anti-Communist Fervor

On the home front, beginning in 1949, fear of domestic communists gripped America. The country spent much of the 1950s under the influence of the Red Scare, led by the virulently anti-communist Senator Joseph McCarthy. McCarthy saw communists everywhere in America and encouraged an atmosphere of hysteria and distrust.

Photo of Senator Joseph McCarthy holding papers.
Photo of Senator Joseph McCarthy. The McCarthy Era was marked by dramatic accusations that communists had infiltrated the highest levels of American society as part of a global conspiracy. Getty Images

Internationally, following World War II, country after country in Eastern Europe had fallen under communist rule, as had China, and the trend was spreading to other nations in Latin America, Africa, and Asia as well. The U.S. felt that it was losing the ​Cold War and needed to "contain" communism.

It was against this backdrop that the first U.S. military advisers were sent to help the French battle the communists of Northern Vietnam in 1950. That same year, the Korean War began, pitting Communist North Korean and Chinese forces against the U.S. and its UN allies.

French Indochina War

The French were fighting in Vietnam to maintain their colonial power and to regain their national pride after the humiliation of World War II. The U.S. government had an interest in the conflict in Indochina from the end of World War II until the mid-1950s when France found itself fighting against a communist insurgency led by Ho Chi Minh.

Throughout the early 1950s, the Viet Minh forces made significant gains. In May 1954, the French suffered a military defeat at Dien Bien Phu and negotiations began to end the conflict.

Following the French withdrawal from Indochina, the solution put in place established a communist government in North Vietnam and a democratic government in South Vietnam. The Americans began supporting the South Vietnamese with political and military advisers in the late 1950s.

Military Assistance Command Vietnam

The Kennedy foreign policy was rooted, of course, in the Cold War, and the increase of American advisers reflected Kennedy’s rhetoric of standing up to communism wherever it might be found.

John Kennedy with Nguyyan Dinh Thuan
Nguyyan Dinh Thuan, Chief Cabinet Minister to President Ngo Dinh Diem of South Vietnam, confers with President Kennedy in his White House office today. Thuan delivered a letter from President Ngo Dinh Diem dealing with the Communist threat to his country. Bettmann Archive / Getty Images

On February 8, 1962, the Kennedy administration formed the Military Assistance Command Vietnam, a military operation intended to accelerate the program of giving military aid to the South Vietnamese government.

As 1963 progressed, the issue of Vietnam became more prominent in America. The role of American advisers increased and by late 1963, there were more than 16,000 Americans on the ground advising South Vietnamese troops.

The Gulf of Tonkin Incident

Following Kennedy’s assassination in November 1963, the administration of Lyndon Johnson continued the same general policies of putting American advisers in the field beside South Vietnamese troops. But things changed with an incident in the summer of 1964.

American naval forces in the Gulf of Tonkin, on the coast of Vietnam, reported being fired upon by North Vietnamese gunboats. There was an exchange of gunfire, though disputes about what exactly happened and what was reported to the public have persisted for decades.

View of U.S.S. Maddox
The U.S.S. Maddox DD-731 was the victim of an 'unprovoked attack' in international waters off Vietnam, the Navy announced in Honolulu 8/1. The attack was made near the Communist Chinese held island of Hainan. Bettmann Archive / Getty Images

Whatever happened in the confrontation, the Johnson administration used the incident to justify a military escalation. The Gulf of Tonkin Resolution was passed by both houses of Congress within days of the naval confrontation. It gave the president broad authority to defend American troops in the region.

The Johnson administration began a series of airstrikes against targets in North Vietnam. It was assumed by Johnson’s advisers that air attacks alone would cause the North Vietnamese to negotiate an end to armed conflict. That did not happen.

Reasons for Escalation

In March 1965, President Johnson ordered U.S. Marine battalions to defend the American airbase at Da Nang, Vietnam. It marked the first time combat troops were inserted into the war. The escalation continued throughout 1965, and by the end of that year, 184,000 American troops were in Vietnam. In 1966, the troop totals rose again to 385,000. By the end of 1967, American troop totals peaked in Vietnam at 490,000.

Throughout the late 1960s, the mood in America transformed. The reasons for entering the Vietnam War no longer seemed so vital, especially when weighed against the cost of the war. The anti-war movement mobilized Americans in vast numbers, and public protest demonstrations against the war became commonplace.

American Pride

During the administration of Richard M. Nixon, the levels of combat troops were reduced from 1969 onward. But there was still considerable support for the war, and Nixon had campaigned in 1968 pledging to bring an "honorable end" to the war.

The sentiment, especially among conservative voices in America, was that the sacrifice of so many killed and wounded in Vietnam would be in vain if America simply withdrew from the war. That attitude was held up to scrutiny in a televised Capitol Hill testimony by a member of the Vietnam Veterans Against the War, future Massachusetts senator, presidential candidate, and secretary of state, John Kerry. On April 22, 1971, speaking of losses in Vietnam and the desire to remain in the war, Kerry asked, “How do you ask a man to be the last man to die for a mistake?”

In the 1972 presidential campaign, Democratic nominee George McGovern campaigned on a platform of withdrawing from Vietnam. McGovern lost in a historic landslide, which seemed, in some part, to be a validation of Nixon’s avoidance of a speedy withdrawal from the war.

President Nixon Standing at Map of Cambodia
April 30, 1970, Washington, DC. In a TV speech to the Nation from the White House, President Nixon announced that several thousand American ground troops entered Cambodia to wipe out Communist headquarters for all military operations against South Vietnam. The President is shown here standing before a map of Cambodia. Bettmann Archive / Getty Images

After Nixon left office as a result of the Watergate scandal, the administration of Gerald Ford continued to support the government of South Vietnam. However, the forces of the South, without American combat support, could not hold off the North Vietnamese and the Viet Cong. The fighting in Vietnam finally ended with the collapse of Saigon in 1975.

Few decisions in American foreign policy have been more consequential than the series of events that led the United States to become involved in the Vietnam War. After decades of conflict, more than 2.7 million Americans served in Vietnam and an estimated 47,424 lost their lives; and still, the reasons why the U.S. entered the Vietnam War to begin with remain controversial.

Kallie Szczepanski contributed to this article.

Additional References

View Article Sources
  1. "Military Advisors In Vietnam: 1963." John F. Kennedy Presidential Library and Museum. National Archives.

  2. Stewart, Richard W., editor. “The U.S. Army in Vietnam: Background, Buildup, and Operations, 1950–1967.” American Military History: The United States Army in a Global Era, 1917–2008, II, Center of Military History, pp. 289–335.

  3. "Military Health History Pocket Card for Health Professions Trainees & Clinicians." Office of Academic Affiliations. U.S. Department of Veterans Affairs.

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McNamara, Robert. "Why Did the US Enter the Vietnam War?" ThoughtCo, Jul. 29, 2021, thoughtco.com/why-did-us-enter-vietnam-war-195158. McNamara, Robert. (2021, July 29). Why Did the US Enter the Vietnam War? Retrieved from https://www.thoughtco.com/why-did-us-enter-vietnam-war-195158 McNamara, Robert. "Why Did the US Enter the Vietnam War?" ThoughtCo. https://www.thoughtco.com/why-did-us-enter-vietnam-war-195158 (accessed May 29, 2023).