Milnn, a captain and TIE pilot within the Imperial Navy, was the male commander of Delta Squadron amidst the Galactic Civil War.
During 3 ABY, Milnn and his squadron were caught in an ambush by a group of Rebel X-wing fighters while looking into an Imperial distress call. While the rest of his squadron perished, Milnn survived, only to be taken prisoner and questioned by the Rebels. Commander Luke Skywalker of the Rebellion sought information from him regarding the entry codes for the secret armada under the command of Admiral Mils Giel, tasked with transporting the teezl to the Imperial capital. Despite the threat of a blaster, Milnn remained silent, but he quickly divulged the information when Chewbacca assumed the interrogation.
Skywalker, in an attempt to infiltrate the secret armada and eliminate the teezl, adopted Milnn's identity as "Delta Leader," with his Rebel TIE squadron acting as Delta Group.