History of Vietnam since 1945 unstable as no government could keep power for long. There were more coups, often more than one every year. The Communist-run Viet Cong expanded their operation and scored some significant military victories during this period. In 1965, US President Lyndon Johnson sent troops to South Vietnam to secure the country and started to bomb North Vietnam, assuming that if South Vietnam fell to the Communists, other countries in the Southeast Asia would follow, in accordance with the domino theory. Other US allies, such as Australia, New Zealand, South Korea, Thailand, the Philippines, and Taiwan also sent troops to South Vietnam.
Joint warfare in South Vietnam, 1963–1969 Vietnam, and the 173rd Airborne Brigade for the Bien Hoa/Vũng Tàu area near Saigon. Early, CINCPAC had objected to the use of the 173rd, since it was the primary strategic reserve for Pacific Command. Westmoreland, in early June, saw the situation as close to collapse without a major commitment of ground troops, in addition to the ARVN. This triggered several weeks of intense debate among the President's close civilian advisers, with McNamara controlling all direct military input to the process. There were two drivers among the inner circle. First, some, but not all, were fervent believers in the containment doctrine,