Near the beginning of the Battle of Poltava sequence, a Swedish officer raises his right hand to order an advance. In the next scene, a close up, his left hand is raised instead.
Incorrect military terminology is used by the Swedish officers in the battle scenes.
None of the cannons can be seen recoiling.
During the Battle of Poltava, when howitzer shells explode in the distance, the explosion can be heard immediately, when at that distance the sound would take a split second to be heard.
Throughout the movie, soldiers are shown turning their heads just before firing muskets (presumably to avoid the flash from the priming pan). Soldiers would have always been trained to aim while firing muskets.