Factual error: Toward the end of the film, General Lee is wearing his open frock with the 3 stars on the collar. However the stars in the movie have six points while the stars that the real General Lee wore in the war were five-pointed stars, as were any other star used as a Confederate rank insignia.
Factual error: Throughout most of the movie, Lee and Jackson are riding the wrong horses. Traveller was a dapple grey horse with dark grey mane and tail, and Little Sorrel was a dark rust-colored horse with a white star on his face. In the movie, Lee is shown riding a white horse with white mane and tail. At the beginning of the movie, Jackson's horse is correctly depicted as a sorrel with a white star. Then Jackson's horse is switched to a red chestnut with white blaze and four white socks.
Factual error: In 1861, neither Stonewall Jackson nor Robert E. Lee had heavy beards. Lee grew his after his resignation, and Jackson grew his during his campaigns.
Factual error: In the scene where Colonel Jackson meets his wife at the train station, the locomotive tender is labeled V&TRR and the coach is the familiar yellow-brown of the Virginia and Truckee Railroad. The V&T was a Nevada shortline connected to the Comstock gold strike that actually financed a huge amount of the Union expenses for fighting the war.
Factual error: Near the beginning of the movie the VMI boys are surrounding a flagpole about to tear the flag off it. The flag is CGI to hide the modern American flag waving there. However, when they zoom in to crowd pulling it down, it is a modern 50 star American flag. It isn't even a brief glimpse. It is there for several seconds and clear as day-modern flag.
Factual error: Throughout the movie, you'll notice some soldiers who are slightly plump, and others that are just plain fat (such as the "Santa-sized" Confederate soldier receiving the rifle from what one would assume to be a gunsmith). Because of strenuous marching and poor supplies (especially in the case of the Confederate army), by the time the Battle of First Bull Run came around, it would be highly unlikely that any of the soldiers would be as fat as those in the movie.
Factual error: The Confederate camp before the July 1861 Battle of Bull Run has shelter tents (AKA pup tents). These tents were first used by the Union army in late spring 1862. Conversely, the Union Army of the Potomac at Chancellorsville in May of 1863 is using common tents - the kind replaced by the shelter tent a year earlier.