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.
1971 in the Vietnam War Chenla II was a major military operation conducted by the Cambodian military (then known as FANK) during the Cambodian Civil War. The Cambodian military failed to dislodge the communist North Vietnamese Army and Viet Cong from territory and suffered heavy casualties. Operation Jefferson Glenn was the last major ground operation in which U.S. troops participated in the Vietnam War. Three battalions of the 101st Airborne patrolled the area west of the city of Huế, called the "rocket belt," to try to prevent communist rocket attacks. The Americans were gradually replaced by soldiers of the South Vietnamese army. The Americans and