Credited to a collective of 19 individuals–including filmmaker Barbara Kopple–this record of testimony given during the 1971 Winter Soldier Investigation in Detroit is more document than documentary, but it may be the most important account we have of America’s tragic encounter with Vietnam. The hearings, organized by Vietnam Veterans Against the War, allowed combat veterans to report, with honesty and unforced eloquence, their observations, experiences, and war crimes (and those crimes’ relation to government policy). Deeply upsetting and long unavailable, this remains essential viewing. 96 min. Reviewed this week in Section 1. Gene Siskel Film Center.