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: Blank firing adaptors are visible on the bow machine guns of Oddball's Shermans as they shoot up the rail yard. (01:00:05)
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.
Other mistake: In the opening credits, character actor Andreas Malandrinos has his last name (as it happened not infrequently throughout his career) misspelled as "Melandrinos" (00:02:55)
Continuity mistake: At the beginning of the interrogation of O'Malley, during the 'cancer prevention' joke the big cigar in the mouth of Coffin Ed moves to the far right corner in an obvious jump in continuity. (00:54:20)