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.
1961 in the Vietnam War of the U.S. Army to respond to Kennedy's emphasis on developing a greater capability in counterinsurgency, although the U.S. Military Assistance Advisory Group began providing counterinsurgency training to the South Vietnamese army (ARVN) and other security forces. The Kennedy Administration debated internally about introducing U.S. combat troops into South Vietnam, but Kennedy decided against ground soldiers. The CIA began assisting Montagnard irregular forces, American pilots began flying combat missions to support South Vietnamese ground forces, and Kennedy authorized the use of herbicides (Agent Orange) to kill vegetation near roads threatened by the Viet Cong. By the end of the year,