Continuity mistake: Just before the final battle begins, the shots pan several times from Shaw, to the sea, and then to the fort. When the camera angle is looking at Shaw, the sky is bright blue. When it shifts to the ocean, the sky instantaneously becomes brownish tan, and then becomes a dismal gray behind the fort.
Continuity mistake: When the men refuse to accept their pay, the Colonel tears his paycheck in half. It tears straight down the middle. There is a brief shot of the men, and the camera returns to the colonel. There is a piece of his check in his hand and the tear is now diagonally across the paper.
Continuity mistake: As the 54th charge Fort Wagner across the beach there is a long range shot of the troops running from the left to the right of the screen. Watch Matthew Broderick. He is holding his large wide-brimmed hat, which he does not wear (or even carry) in previous and subsequent scenes!
Continuity mistake: In the scene where the 54th is on parade, Shaw commands "eyes right" and looks to his right and points his sword down to the right. Then the next shot is a brief shot of his parents and then when they return to Shaw, his sword is pointing up in the normal marching position. There was no audible command to stop saluting.
Continuity mistake: When Colonels Shaw and Montgomery are in Darien, Georgia, Montgomery shoots a soldier (apparently in the heart) for touching a white woman. When the troops are marching out of the town, the soldier who was shot has miraculously felt better, gotten back up and joined the ranks.