Factual error: During the first few minutes of the film we see Major Payne report into the General. Major Payne then salutes, however, he does not have a cover on his head. As per USMC/Naval Customs and Courtesies, Marines only render the proper greeting of the day when reporting to a superior officer without a cover, they don't salute. (00:03:20)
Factual error: When Payne is at the train station considering boarding it for Washington DC to return to active duty, it's a southbound train. The station he's in is Ashland, VA - DC is north from there.