The struggle between French colonial forces and native Vietnamese citizens supported by Chinese communists was one of the root causes of the Vietnam War. United States forces entered the conflict in support of the French in order to fight communism. When the French left, the Americans fought the war alone.
The Americans had been working with the anti-communist side in Vietnam since 1950. The Vietnamese Diem administration was corrupt and proved ineffective in fighting the powerful and communist-supported Ho Chi Minh. In August 1964, Vietnamese forces fired on an American destroyer in the Gulf of Tonkin, and America retaliated with airstrikes. By 1965, the United States was fully committed in Vietnam, with over 60,000 American troops on its ground.