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.
South Korea in the Vietnam War government.The US had also withdrew the 7th Division from the Korean peninsula while placing the 2nd Division in the rear which soured relations between Korea and the US. In 1969 the South Korean army accounted for 9% of the foreign troops stationed in South Vietnam (US Army 475,200, ROK Army 49,755), by the end of 1972, the South Korean army accounted for 60.5% of foreign troops (US Army 24,200, ROK Army 37,438). US Marine Aviation assets that supported the Blue Dragon troops withdrew completely in May 1971 while the combat role of Korean troops continued. Around the time of the