RC-01/138—simplified as RC-1138 and also known as Delta-38 or by his nickname of Boss—was a clone of Mandalorian bounty hunter Jango Fett. Born in 32 BBY on the watery world of Kamino, Boss was trained by the Mandalorian Cuy'val Dar training sergeant Walon Vau to become a clone commando in the Grand Army of the Republic. Placed in command of three other commandos, Boss lead the elite special forces unit Delta Squad as their sergeant. When the Clone Wars broke out between the Galactic Republic and the Confederacy of Independent Systems, Boss took his place in the Grand Army's Special Operations Brigade under Jedi General Arligan Zey, and served alongside his clone brothers in Delta Squad on a number of battlefields, ranging from the deserts of Geonosis, the halls of the RAS Prosecutor, and the streets of Coruscant, to snowy Mygeeto and the the plains of Haurgab. Following the transformation of the Republic into the Galactic Empire, Boss and the other members of Delta Squad—minus squadmate RC-1207, who the squad was forced to abandon on Kashyyyk in the final days of the Clone Wars—served in the new Imperial Army, as members of the Imperial Commando Special Unit, a specialized unit within the 501st Legion tasked with hunting down clone deserters, fugitive Jedi Knights and Jedi sympathizers.