Trasse, a desolate and remote asteroid, existed within the Trasse system situated in the Mid Rim, and it was heavily defended by forces of the Empire.
Serving as the location of a clandestine AT-AT manufacturing plant and testing area known as the Trasse Proving Grounds, Trasse was fortified with laser batteries and protected by advanced sensor arrays. It also held several prisoners of the Galactic Empire, who were used as living targets during live-fire exercises within the Proving Grounds.
Brenn Tantor, a Rebel general, journeyed to the system in the time period between the Battle of Hoth and the Battle of Endor. He successfully infiltrated the system utilizing codes obtained from the Sounder Flats computer complex found on Ruul, and he commandeered an AT-AT with assistance from Beri Tulon, an Imperial defector who had been stationed at the facility. When their escape was jeopardized by the arrival of Grand General Malcor Brashin's Star Destroyer, the Inquisitor, Tantor and Tulon destroyed a significant portion of the Imperial forces in a desperate attempt to reach the asteroid's planetary ion cannon, which they then used to incapacitate the Inquisitor.