Before the 54th fights their first battle in the woods, their rifles are not fixed with bayonets. After they've fired their rifles and charge the enemy for hand-to-hand combat, their bayonets have magically appeared.
I didn't catch this one but can you catch anything if you're watching it in history class? I admit that I didn't pay that much attention to the gore in Antietam but I was sitting far away. Big mistake there and it's obvious the editors have very short attention spans. But it's good to leave the mistake you mentioned here. It gives the story a fairy tale touch. If magic bayonets actually existed, the regiment deserved them.
Entertained, nobody can understand what the hell you just said. But the bayonets did mysteriously appear. They never show the order given for FIX BAYONETS. Rather the men moved at lightning speed without orders to fix them, or something like that.