According to Wikipedia:
The screenplay by Kevin Jarre was based on the books Lay This Laurel (1973) by Lincoln Kirstein and One Gallant Rush (1965) by Peter Burchard and the personal letters of Shaw. The film depicts the soldiers of the 54th from the formation of their regiment to their heroic actions at the Second Battle of Fort Wagner.
There is also an excellent documentary, The Massachusetts 54th Colored Infantry by the PBS program American Experience.
On July 18, 1863, at dusk, the Black soldiers of the Massachusetts 54th Volunteer Infantry of the U.S. Army charged the walls of Fort Wagner, a fortification on Morris Island off Charleston Harbor in South Carolina. Because Fort Wagner covered the southern entrance to the harbor, it was key to enabling the U.S. government to take the city.
The 600 soldiers of the 54th made up the first Black regiment for the Union, organized after the Emancipation Proclamation called for the enlistment of African American soldiers. The 54th’s leader was a Boston abolitionist from a leading family: Colonel Robert Gould Shaw.
Continue reading from Richardson’s article (at heathercoxrichardson.substack.com) …