*Takes the nerd cap and puts it on* The Ecliptic Invaders were defectors from the Empire who came to the Rebellion after a mutiny on the Rand Ecliptic, and Imperial frigate - complicated by the fact that there were no less than three individual cells of Rebels aboard the ship. Which made things rather confusing when it came time to actually take the ship.
As a result of the mutiny, Captain Soontir Fel of the Presbelt IV Imperial Academy, was removed from his post as a flight instructor because two of the senior mutineers - Derek "Hobbie" Klivian and Biggs Darklighter - were his students. As a result, he was not assigned to Grand Moff Tarkin's honor guard aboard the Death Star battlestation and was instead assigned to the 181st Imperial Fighter Wing as commander of the Second Squadron under the overall command of Colonel Evir Derricote. When the Second Battle of Ord Bniir was won by the 2/181st on the same day that the Death Star was destroyed, Soontir Fel was promoted to major and placed in charge of turning the 181st Imperial Fighter Group into an elite unit, which would become the most feared TIE Interceptor group in the whole Empire.