Revealing mistake: In the shot where Benjamin is riding his horse to the top of the hill, the camera pans from left to right and in the distance is the British army. But if you look to the left the trees are way too huge (a bad scale). If Benjamin had ten militamen cut one down, it would have wiped out 1/4 of the British army shown.
Revealing mistake: During the battle at the end, while Martin and Tavington are fighting, you can tell the battle going on behind them is a blue screen because they are often moving slower than the battle and vice-versa.
Revealing mistake: The obviously painted backdrops of Charlestown showed that the scene was not shot in location.