History of the United States (1964–1980)
The growing Watergate scandal was a major disaster for Nixon, eroding his political support in public opinion and in Washington. However he did manage to secure large-scale funding for South Vietnam, much of which was wasted. The United States withdrew its troops from Vietnam before the Paris Peace Accords in 1973. However, Watergate resulted in significant Democrat gains in the 1974 midterm elections and when the new 94th Congress convened the following January, it immediately voted to terminate all aid to South Vietnam in addition to passing a bill forbidding all further US military intervention in Southeast Asia. President Ford was against this, but as Congress had a veto-proof majority, he was forced to accept. South Vietnam rapidly collapsed as the North invaded it in force, and Saigon fell to the NVA on April 30, 1975. Later nearly one million Vietnamese managed to flee to the U.S. as refugees. The impact on the U.S. was muted, with few political recriminations, but it did leave a "Vietnam Syndrome" that cautioned against further military interventions anywhere else. Nixon (and his next two successors Ford and Carter) had dropped the containment policy and were not willing to intervene anywhere.
War in Vietnam (1959–1963)
While the visible guerilla incidents increased gradually, the key policy decisions by the North were made in 1959. Early in this period, there was a greater degree of conflict in Laos than in South Vietnam. US combat involvement was, at first, greater in Laos, but the activity of advisors, and increasingly US direct support to South Vietnamese soldiers, increased, under US military authority, in late 1959 and early 1960. Communications intercepts in 1959, for example, confirmed the start of the Ho Chi Minh trail and other preparation for large-scale fighting. North Vietnam declared its public support for communist insurgents in South Vietnam. The communist forces in South Vietnam established the National Front for the Liberation of South Vietnam (Viet Cong). At the same time, the United States helped the South Vietnamese regime conduct its war strategy. Despite this assistance, the communist forces still won on the battlefield, fighting several large campaigns next to the big cities. Diệm was unable to take control of political crisis and was overthrown by the Council of Revolutionary Military (some documents of both sides suggest that it was the United States which had given the green light for this coup). After several years of chaos, the Ngô Đình Diệm government came to an end in 1963 and South Vietnam then fell into management crisis.