https://en.wikipedia.org/wiki/Fall_of_Saigon
''The Fall of Saigon,[1][2] also known as the Liberation of Saigon,[3] ''
was the capture of Saigon, the capital of South Vietnam, by the People's Army of Vietnam (PAVN) and the Viet Cong on 30 April 1975. The event marked the end of the Vietnam War and the start of a transition period to the formal reunification of Vietnam into the Socialist Republic of Vietnam.[4]
The PAVN, under the command of General Văn Tiến Dũng, began their final attack on Saigon on April 29, 1975, with the Army of the Republic of Vietnam (ARVN) forces commanded by General Nguyễn Văn Toàn suffering a heavy artillery bombardment.
By the afternoon of the next day, the PAVN had occupied the important points of the city and raised their flag over the South Vietnamese presidential palace. The city was renamed Hồ Chí Minh City, after the late North Vietnamese President Hồ Chí Minh.
The capture of the city was preceded by Operation Frequent Wind, the evacuation of almost all the American civilian and military personnel in Saigon, along with tens of thousands of South Vietnamese civilians who had been associated with the Republic of Vietnam.
A few Americans chose not to be evacuated.
US ground combat units had left South Vietnam more than two years prior to the fall of Saigon and were not available to assist with either the defense of Saigon or the evacuation.[5]
The evacuation was the largest helicopter evacuation in history.[6]:
202 In addition to the flight of refugees, the end of the war and the institution of new rules by the communists contributed to a decline in the city's population.[7]