The American conception of Vietnam as a cold war battleground largely ignored the struggle for social justice and national sovereignty occurring within the country. After China became a communist state in 1949, the stability of Japan became of great importance to Washington, and Japanese development required access to the markets and raw materials of Southeast Asia. This apprehension, an overestimation of American power, and an underestimation of Vietnamese communist strength locked all administrations from 1950 through the 1960s into a firm anticommunist stand in Vietnam.

Vietnam began with President Dwight D. Eisenhower, who increased the level of aid to the French but continued to avoid military intervention. Following there was an international conference at Geneva, Switzerland. There a cease-fire was arranged which provided for a North-South partition of Vietnam until elections could be held. The United States was not a party to the Geneva Agreements and began to foster the creation of a Vietnamese regime in South Vietnam to rival that of Ho in the North. Eisenhower had then proclaimed the "domino theory," which was that, if the communists succeeded in controlling Vietnam, they would eventually dominate all of Southeast Asia. With support from Washington, South Vietnam's autocratic president Ngo Dinh Diem, resisted holding an election on the reunification of Vietnam. Nation building was failing in the South, and, in 1960, communist cadres created the National Liberation Front, or Vietcong as its enemies called it, to challenge the Diem regime.

By 1963, President John F. Kennedy had tripled American aid to South Vietnam and expanded the number of military advisers there from less than seven hundred to more than sixteen thousand. But the Diem government still failed to show economic or political progress. Finally, after receiving assurances of noninterference from U.S. officials, South Vietnamese military officers had Diem murdered.

Diem's death left a big gap open for leadership in South Vietnam, and the survival of the Saigon regime was in jeopardy. However, a larger war in Vietnam also raised the risk of a military clash with China. In 1964 Johnson authorized limited bombing raids on North Vietnam and had an agreement with Congress allowing him to use military forces in Vietnam by, using as a provocation alleged North Vietnamese attacks on U.S. Navy vessels in the Gulf of Tonkin. By 1968 Johnson had stationed 575,000 troops in South Vietnam to prevent its supposed domination by China. He also feared that Vietnam''s fall would lead to a domino like communist successes in Southeast Asia. Supporting these ground troops was a tremendous air bombardment of North Vietnam that surpassed the total tonnage dropped on Germany, Italy, and Japan in World War II.

Gen. William Westmoreland, the U.S. commander in Vietnam, pursued an attrition strategy designed to inflict heavy losses on the enemy. His headquarters was claiming that the crossover point had been reached and that enemy strength was being destroyed faster than it could be replenished. But the communists' Tet offensive launched in January 1968 quickly extinguished any hope. The Vietcong struck throughout South Vietnam, including a penetration of the U.S. embassy compound in Saigon. American and South Vietnamese forces eventually repulsed the offensive and inflicted heavy losses on the Vietcong, but the fighting had exposed the reality that a quick end of the war was not in sight.

Following the Tet offensive, American leaders began a slow and agonizing reduction of U.S. involvement. Johnson limited the bombing, began peace talks with Hanoi. His successor, Richard M. Nixon, announced a program of Vietnamization, which basically represented a return to the Eisenhower and Kennedy policies of helping Vietnamese forces fight the war. Nixon gradually reduced U.S. ground troops in Vietnam, but he increased the bombing; the tonnage dropped after 1969 exceeded the levels dropped by Johnson. Nixon also expanded air and ground operations into Cambodia and Laos in attempts to block enemy supply routes along Vietnam's borders. He traveled to Moscow and Beijing for talks and sent his aide Henry A. Kissinger to Paris for secret negotiations with the North Vietnamese. In January 1973, the United States and North Vietnam signed the Paris Peace Agreement, which provided for the withdrawal of all remaining U.S. forces from Vietnam, the return of U.S. prisoners of war, and a cease-fire.

During the decade of direct U.S. military participation in Vietnam beginning in 1964, the goal was to preserve a separate, independent, noncommunist government in South Vietnam, but after April 1975, the communist Democratic Republic of Vietnam ruled the entire nation.