During the American Civil War, Captain Robert Shaw, injured at Antietam, is sent home to Boston on medical leave. Shaw accepts a promotion to colonel commanding the 54th Massachusetts Infantry Regiment, one of the first all-black regiments in the Union Army. He asks his friend Cabot Forbes to serve as his second in command, with the rank of major. Their first volunteer is another friend, Thomas Searles, a bookish, free African-American. Other recruits include John Rawlins, Jupiter Sharts, Trip, and a mute teenage drummer boy.