Bohannon and Lt. Griggs between them provide a fairly accurate account of the fight for Burnside Bridge during the Battle of Antietam (or Sharpsburg, as Confederates like Bohannon chose to call it). However it is unlikely that Bohannon would have been there to witness the fight since the bridge was defended by two regiments of Georgia infantry and Bohannon is from Mississippi. There were a number of Mississippi regiments at Antietam but all were engaged on the Confederate left, approximately one to two miles north of Burnside Bridge.
Though Christopher Heyerdahl's character is always credited as "The Swede", Mr. Durant (Colm Meaney) calls him Mr. Gunderson when chastising him.