Warning: Wikipedia contains spoilers
The movie is about twelve Allied soldiers, all imprisoned and facing sentences of death or long terms of imprisonment, who are given a chance to go on a very risky mission to get their sentences set aside.
The mission, led by Reisman (Marvin) as a prelude to D-day, is an assault on a chateau used as a resort by many of the German officers.
Of the twelve, only Wladislaw (Number 11) (Bronson) survives. Group troublemaker Franco (Cassavetes) almost survives, but gets shot in the back just as they are leaving the operation.
Also worth noting is war movie fixture Savalas, who plays the highly religious, psychologically unstable Archer Maggot. Sutherland humorously embarrasses Marvin when called on to inspect other troops.