Lon Nol fell from power in Cambodia in April 1975, replaced by a brutal Khmer Rouge regime led by Pol Pot. The Khmer Rouge killed an estimated 2 million people during the next three years, at which point the North Vietnamese went to war and chased them into hiding. Thieu, overwhelmed by a North Vietnamese military offensive, was forced to resign on April 21, 1975. As his loyalists scrambled desperately to climb aboard United States helicopters, Hanoi ran up its flag in Saigon on May 1 and renamed the capital Ho Chi Minh City. South Vietnam was a state no more.
