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.
Brown-water navy
On December 18, 1965, for the first time since the American Civil War, the United States Navy formalized its new, brown-water navy in Vietnam. Initially, the brown-water navy patrolled the inland waterways of the Mekong River, primarily with South Vietnamese river craft (RAG—River Assault Groups) boats, which were mostly inherited from the French Navy during the previous war and in turn, had been received from the U.S., as military aid, in the French fight against the Viet Minh, the Communist-led Vietnamese alliance. As the new fiberglass Patrol Boat, River using water jet propulsion, became available, it became the main interdiction vessel for patrolling the Vietnamese Mekong River country.