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.
1965 in the Vietnam War revealed that Thao was a communist agent. General William Westmoreland, commander of MACV, requested that two battalions of United States Marines be assigned to protect the airbase at Da Nang from the increasing threat of attacks by the Viet Cong. General Khánh departed South Vietnam. He was persuaded to leave by his fellow generals and by Colonel Wilson of MACV. Air Marshall Nguyễn Cao Kỳ became the de facto leader of South Vietnam. The first South Korean troops arrived in South Vietnam. The number of South Korean troops in South Vietnam would total 49,755 by 1969. The U.S. paid most