United States involvement in the Vietnam War began shortly after the end of World War II in Asia, first in an extremely limited capacity and escalating over a period of 20 years. The U.S. military presence peaked in April 1969, with 543,000 American combat troops stationed in Vietnam. By the conclusion of the United States's involvement in 1973, over 3.1 million Americans had been stationed in Vietnam.

The Vietnam War was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was a major conflict of the Cold War. While the war was officially fought between North Vietnam and South Vietnam, the north was supported by the Soviet Union, China, and other communist states, while the south was supported by the United States and other anti-communist allies, making the war a proxy war between the United States and the Soviet Union. It lasted almost 20 years, with direct U.S. military involvement ending in 1973. The conflict also spilled over into neighboring states, exacerbating the Laotian Civil War and the Cambodian Civil War, which ended with all three countries officially becoming communist states by 1976.