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.
Vietnam War South Korea (a.k.a. the Republic of Korea, ROK) had the second-largest contingent of foreign troops in South Vietnam after the United States. In November 1961, President Park Chung-hee proposed South Korean participation in the war to John F. Kennedy, but Kennedy disagreed as they were not SEATO treaty members. On 1 May 1964, Lyndon Johnson agreed to permit South Korean participation under the Many-Flags Program in return for monetary compensation. The first South Korean troops began arriving in 1964 and large combat formations began arriving a year later. The ROK Marine Corps dispatched their 2nd Marine Brigade, while the ROK