The Sentinel, a Golan II Space Defense SpaceGun, served the Alliance to Restore the Republic at Kothlis II. Its purpose was to provide a strong defense for the primary installation on Kothlis II against assaults from the forces of the Galactic Empire.
In the course of the Battle of Kothlis, the Rebel Alliance's installations came under attack from the Executor and the Avenger; these ships had been dispatched by the Galactic Empire in order to retrieve a stolen computer containing the schematics for the Death Star II. As the nearer target, Sentinel endured heavy bombardment from TIE/sa bombers deployed from the Avenger. Ultimately, the base succumbed to focused enemy fire, thereby rendering Kothlis II defenseless.