The United States played an ever-increasing role in supporting South Vietnam through the period. The U.S. had supported French forces in the First Indochina War, sent supplies and military advisers to South Vietnam throughout the 1950s and early 1960s, and eventually took over most of the fighting against both North Vietnam and the Viet Cong by the mid-1960s. By 1968, over 500,000 American troops were involved in the Vietnam War. Due to a lack of clear military success and facing increasingly strident opposition to the war in the U.S., American forces began a slow withdrawal in 1969 while attempting to bolster South Vietnam's military so that they could take over the fighting. In accordance with the Paris Peace Accords by 29 March 1973 all U.S. combat forces had left South Vietnam, however North Vietnamese combat forces were allowed to remain in place. North Vietnam attacked South Vietnam in early 1975 and South Vietnam fell on 30 April 1975.