Factual error: In some of the scenes in the video during their time at Readville camp, they celebrate Christmas. In actuality, the first volunteers arrived at Readville in February of 1863, and Shaw died in July of 1863, along with most of the regiment, so there is no possibility of having a Christmas during that time.
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.
Factual error: During the burial scene at the end of the movie, the corpses of the 54th soldiers are shown with only their shoes removed. In reality, the corpses of the 54th dead were stripped of all usable clothing, as the South was desparate for any uniform parts (source: "A Brave, Black Regiment" by Louis Emilio). At the very least, the corpses of the officers would have been picked clean by souvenir hunters.
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.
Factual error: During the training of the regiment, there is one scene where Colonel Shaw is shown practising his swordsmanship. A row of stakes has been placed in the ground and a watermelon tied to each one which he slices apart with his sword as he gallops past.The caption tells us that it is February 1863 in Massachusetts. There is no way you could get fresh watermelons in that state at that time of year in 1863.
Factual error: One of the characters of Glory is a mute drummer boy. However, 54th Mass. was established as a regiment composed exclusively of the cream of Northern black society. Because only the most healthy and robust African-Americans were allowed to enlist in this regiment, many recruits were rejected for medical reasons. Union military officials of 54th Mass. would not have recruited any handicapped person.
Audio problem: In the scene where Matthew Broderick is addressing the potential members of the 54th on horseback (right after he accepts the position), the army band is playing, but the visuals don't match the music. While we hear drumrolls, we only see single hits on the snare drums by the actors. And at least one drummer is playing in mid-air.
Other mistake: In the scene where muskets are issued to the 54th Massachusetts, only Pvt. Jupiter Sharts is revealed to be a marksman worthy of training the other troops by virtue of having previously hunted squirrels. The camera then zooms to a closeup of Pvt. Sharts aiming down the barrel with the wrong eye closed.