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.
History of the United States Army
The Vietnam War is often regarded as a low point in the Army's record due to the extensive use of drafted enlisted personnel versus mobilization of Army Reserve and Army National Guard personnel, the unpopularity of the war with the American public, and frustrating restrictions placed on the Army by U.S. political leaders (i.e., no invasion of communist-held North Vietnam). While American forces had been stationed in the Republic of Vietnam since 1959, in intelligence and advisory/training roles, they did not deploy in large numbers until 1965, after the Gulf of Tonkin Incident. American forces effectively established and maintained control of the "traditional" battlefield, however they struggled to counter the guerrilla hit and run tactics of the communist Viet Cong and the North Vietnamese Army. On a tactical level, American soldiers (and the U.S. military as a whole) did not lose a sizable battle. For instance in the Tet Offensive in 1968, the U.S. Army turned a large scale attack by communist forces into a massive defeat of the Viet Cong on the battlefield (though at the time the offensive sapped the political will of the American public) which permanently weakened the guerrilla force. Thereafter, most large scale engagements were fought with the regular North Vietnamese Army. In 1973 domestic political opposition to the war finally forced a U.S. withdrawal. In 1975, Vietnam was unified under a communist government.