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.
1963 in the Vietnam War 25 percent more than the total killed in the previous year. North Vietnam had infiltrated about 40,000 cadres and fighters into South Vietnam over a period of several years. They made up about 50 percent of the Viet Cong army and 80 percent of political operatives and technical personnel. They consisted mostly of southerners who had migrated north in 1954–1955 to reside in a communist state rather than remain in South Vietnam. Units of the North Vietnamese army had not yet been dispatched to South Vietnam. 1963 in the Vietnam War The defeat of the South Vietnamese Army (ARVN) in