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.
Sino-Vietnamese War
The United States played an ever-increasing role in supporting South Vietnam through the period. The U.S. had supported French forces in the First Indochina War, sent supplies and military advisers to South Vietnam throughout the 1950s and early 1960s, and eventually took over most of the fighting against both North Vietnam and the Viet Cong by the mid-1960s. By 1968, over 500,000 American troops were involved in the Vietnam War. Due to a lack of clear military success and facing increasingly strident opposition to the war in the U.S., American forces began a slow withdrawal in 1969 while attempting to bolster South Vietnam's military so that they could take over the fighting. In accordance with the Paris Peace Accords by 29 March 1973 all U.S. combat forces had left South Vietnam, however North Vietnamese combat forces were allowed to remain in place. North Vietnam attacked South Vietnam in early 1975 and South Vietnam fell on 30 April 1975.