Factual error: During the battle over the fort the British shoot a red flare into the sky. The British army learnt of the effectiveness of rocket weapons when fighting in India in the 1790s. In 1804, rockets (developed by Colonel William Congreve) were introduced into British service. The rocket flare was developed around this time (also by Colonel Congreve). This film is set in the 1750s - the British army would not have had rocket flares (source: Taylor, J.W.R (1970). Rockets & Missiles, Hamlyn, London. PP. 6-10). (00:34:30)
Factual error: Toward the beginning of the film, when Natty Bumppo first arrives at this friends' cabin, he mentions that he was coming from Schuylerville. This is an anachronism as Schuylerville, NY, was named after the victorious General Schuyler at the Battle of Saratoga in 1779, which would not take place until 20 years after the events of the film. The town would not assume the name for another 50 years after that.
Factual error: In real life, Colonel Monro and the Marquis de la Montcalm never met face to face to discuss surrendering Fort William Henry. Monro was also not scalped but died of illness months after he surrendered.