The "Winter Soldier Investigation" was a media event sponsored by the Vietnam Veterans Against the War (VVAW) from January 31, 1971 – February 2, 1971. It was intended to publicize war crimes and atrocities by the United States Armed Forces and their allies in the Vietnam War. The VVAW challenged the morality and conduct of the war by showing the direct relationship between military policies and war crimes in Vietnam. The three-day gathering of 109 veterans and 16 civilians took place in Detroit, Michigan. Discharged servicemen from each branch of military service, as well as civilian contractors, medical personnel and academics, all gave testimony about war crimes they had committed or witnessed during the years of 1963–1970.
With the exception of Pacifica Radio, the event was not covered extensively outside Detroit. However, several journalists and a film crew recorded the event, and a documentary film called Winter Soldier was released in 1972. A complete transcript was later entered into the Congressional Record by Senator Mark Hatfield, and discussed in the Fulbright Hearings in April and May 1971, convened by Senator J. William Fulbright, chair of the United States Senate Committee on Foreign Relations.
Prompted by numerous investigations into war crimes such as the Russell Tribunal, National Veterans Inquiry and Citizens Commission of Inquiry (CCI), the Vietnam Veterans Against the War wanted to have a large scale public hearing. With the courts martial for the My Lai Massacre making front page news, and the recent disclosure by members of the Central Intelligence Agency's Phoenix Program of its record of human rights violations in Vietnam, the VVAW was determined to expose a broad pattern of war crimes in Vietnam. The Winter Soldier Investigation (WSI) was intended to prove that massacres like the My Lai massacre were not isolated and rare occurrences, but were instead the frequent and predictable result of official American war policy.