The Vietnam War was a war of national liberation in which the Vietnamese people fought to resist U.S. aggression and to unify the country. In 1954, when Vietnam had won the war of resistance against French aggression (1946-1954), North Vietnam was liberated. The United States, which had replaced France, controlled South Vietnam, obstructing unification of the country. Starting in 1959, Vietnamese people in the South waged armed struggle against the U.S.-supported autocracy and U.S. interference. In August 1964 the United States bombed North Vietnam, and in March 1965 it sent troops to the South. Confronted with the firm resistance of the Vietnamese people, on January 27, 1973, the U.S. had to sign the Agreement on Ending the War and Restoring Peace in Vietnam and withdraw its troops from the South. On May 1, 1975, South Vietnam was liberated.