Trey Callum was a Human male sergeant major of the Rebel Alliance Special Forces during the height of the Galactic Civil War. Formerly a member of the Imperial officer corps, Callum defected to the Alliance to fight the Galactic Empire. Under the overall leadership of Colonel Ledick Firest, Callum commanded a squad of Special Forces soldiers at Outpost Beta on the Echo Base defensive perimeter during the Battle of Hoth in 3 ABY. Callum was the first to report to Echo Base the presence of Imperial All Terrain Armored Transport walkers advancing toward the base during the opening stages of the battle, and he was killed during the first barrage of AT-AT blasterfire.