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.
1947–50 in the Vietnam War communist activity was coordinated worldwide. Thus, the attack on South Korea caused the U.S. to become more concerned about the Việt Minh insurgency in Vietnam. Việt Minh forces were estimated to have grown to 250,000 personnel, including 120,000 in regular units organized into divisions. The remaining troops were regional and popular and primarily concerned with defense and security. An estimated 15,000 Chinese, in both Vietnam and China, assisted the Việt Minh with training, technicians, and advisers. The French had about 150,000 soldiers in Vietnam. The pro-French Vietnamese army numbered about 16,000 The first U.S. military advisers to Vietnam arrived in