Other mistake: When the Japanese planes take off for Pearl Harbor, some of the 3 man torpedo planes only have a pilot.
Deliberate mistake: There are no lights ever to be found in the underground world and the ceiling is literally the surface's ground, but there is still a perfect level of lighting regardless.
Revealing mistake: The cannons shown are firing blank charges, which produce no recoil. Recoil has been simulated by towing the guns backwards when they fire. The problem is, there is always a distinct delay between the discharge and the "recoil." The cannon also seem to largely fire explosive shells. At no point do we actually see a cannon ball rolling or bouncing along the ground or into any group of soldiers.
Factual error: During the scene where Clint Eastwood is trying to convince Don Rickles to join in the heist, there is a box of Almond Joy candy bars behind Don's head. They weren't introduced until 1946.
Continuity mistake: When the police catches the pickpocketer at the beginning, they literally lift him off the ground. There is a close-up shot in between, and the lack of continuity is apparent in the hand position of the man. Not just that: vehicles obviously disappear and appear in every cut.
