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.
1973 in the Vietnam War Nixon promised continued economic aid to South Vietnam, dependent upon U.S. congressional approval, and Thieu pledged to never ask the United States to reintroduce American troops into South Vietnam. The US and North Vietnam issued a joint communique calling on all parties to observe the 28 January ceasefire agreement with effect from 15 June. The Case–Church Amendment approved by the U.S. Congress and signed into law prohibited further U.S. military activity in Vietnam, Laos and Cambodia after 15 August 1973. This ended direct U.S. military involvement in the Vietnam War, although the U.S. continued to provide military equipment and economic