Trivia: Not really a mistake, given the need for drama in a war film, but the mission takes place the evening before D-Day, meaning the Allies had complete air supremacy, and knew the exact time, date and place of the meeting of the German officers, this mission would never have taken place. The brightly lit chateau would have been flattened by a squadron of heavy bombers. Lee Marvin, an experienced combat veteran, pointed this out to the producers and was told to keep his opinions to himself.