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 were destroyed. Presidential adviser and future Secretary of Defense Clark Clifford in a letter to President Johnson said, "I believe our ground forces in South Vietnam should be kept to a minimum, consistent with the protection of our installations and property in that country ... This could be a quagmire. It could turn into an open end commitment on our part that would take more and more ground troops, without a realistic hope of ultimate victory." "Quagmire" would later become a common word use to describe U.S. involvement in the Vietnam War. Eight hundred soldiers of the Australian Defence Force