Antietam (Sharpsburg) was one of the bloodiest battles in the Civil War. The battle took place on Union soil in 1862. More than 23,000 people had died or were injured. The battle was so gruesome with death that John, a correspondent, had nightmares and possible PTSD. In the movie, we actually see John freaking out in bed and sweating. Kathy Reynolds later came in and helped John go back to sleep.