In the final year of the Vietnam War, a series of offensives by the North Vietnamese led to the fall of the South Vietnamese capital Saigon on April 30, 1975.

As the North Vietnamese Viet Cong approached Saigon, South Vietnamese citizens and American personnel fled before them, and the U.S. government began a program of mass evacuations. People were helicoptered away, sometimes under fire, to waiting American warships. There were scenes of chaos as desperate people tried to escape.

The final phase of the evacuation was code-named Operation Frequent Wind. The American Embassy had previously distributed a booklet to its citizens, called "Standard Instruction and Advice to Civilians in an Emergency" (SAFE). This included a map of Saigon showing areas where they would be picked up when the signal was given. The signal, to be broadcast on Armed Forces Radio, was ""The temperature in Saigon is 105 degrees and rising," followed by the playing of "White Christmas."

Frequent Wind was carried out on April 29 and 30. Such was the speed of the evacuation and the number of people involved that the ships became overwhelmed with people and the helicopters that had brought them. Orders were given to push surplus helicopters over the sides of the ships to make room for more. Some pilots were told to drop off their passengers, then ditch their machines in the sea, bailing out at the last moment to be picked up by waiting rescue boats.

Over 7,000 people were evacuated in Operation Frequent Wind.