The parties' federation was functional during Nguyễn Văn Thiệu's tenure as President and changed its name to "Social Democratic Alliance" in 1973. However, with the Vietnamization policy adopted by U.S. President Richard Nixon, South Vietnam inexorably started its collapse. The Paris Peace Accords of 1973 was a turning point in the war, causing the end of American intervention in Vietnam. Despite the peace agreement between communist North Vietnam and capitalist South Vietnam, in 1975 North Vietnam broke the peace and started the takeover of South Vietnam. Since the United States refused another intervention, South Vietnam collapsed after the Fall of Saigon, causing the reunification of Vietnam under communist rule.