In the Florida Campaign, Montgomery was placed in command of a brigade, containing the Fifty-fourth Massachusetts and First North Carolina Colored Volunteers (later known as the Thirty-fifth United States Colored Troops). One of his regiments was as yet untried in combat, while the other was the most famous black unit of the entire war. In the battle his brigade helped protect the withdrawal of the defeated Union army, allowing it to escape back into the Jacksonville defenses. Montgomery's career declined rapidly after Olustee, and he resigned his commission in September 1864.
Colonel Montgomery's official report of the battle
Wikiepedia page on James Montgomery
Union Order of Battle
Battle of Olustee Home Page
http://battleofolustee.org/