Squad 40 was a unit of Imperial commandos that belonged to the Imperial Commando Special Unit within the ranks of the 501st Legion. This squad was assembled not long after the establishment of the Galactic Empire, and its members were comprised of commandos who had survived the era of the Grand Army of the Republic.
Squad 40's inaugural mission involved the capture of Jilam Kester, an Antarian Ranger suspected of aiding Jedi in their escape. When Squad 40 raided Kester's hideout, they were taken by surprise when they encountered Jedi Master Iri Camas, the former head of the Special Operations Brigade and their previous commander. Following their orders, they tried to subdue him, but Camas created a diversion that allowed Kester to get away. Ultimately, Camas made the ultimate sacrifice, detonating a gas pipe and killing Bry in the explosion after Bry was struck down by Camas's lightsaber. After Bry's demise, Ennen refused to abandon his comrade's body until Bry received a proper Corellian cremation. Roly Melusar, their new commanding officer, kept that promise and ensured he was properly cremated.
Later, they embarked on a mission within the undercity of Coruscant, in pursuit of a man they believed to be a Jedi. Upon Ennen killing the man, they were shocked to find that he was merely a common thief who had acquired the lightsaber from a Jedi's corpse or found it on the street after Order 66. Ennen later took his own life, burdened by both Bry's death and the guilt of killing a civilian. Subsequently, they were assigned the task of eliminating a Jedi named Borik Yelgo on the Coth Fuuras space station. After searching through the crowds of civilians, Squad 40 located the Jedi, issued a warning command, and then the Jedi ran and was cornered by the gate leading to the docking area. There, Squad 40 surrounded the Jedi and opened fire, though this was unsuccessful because Yelgo deflected most of the blaster bolts and jumped off the gate behind Squad 40. Seeing as there was no where to go Yelgo used the force to grip and attempted to throw a heavy piece of transparisteel at Darman, which was stopped when Rede shot at the glass above Yelgo and distracted him giving Rede enough time to come face to face with Yelgo and then terminate him with two subsequent rounds from his DC-15 sidearm.