The 501st Legion, initially created as the 501st Clone Battalion under the Grand Army of the Republic and later joining the Imperial Army as the 501st Imperial Legion, the 501st Stormtrooper Legion and nicknamed "Vader's Fist"—was an elite stormtrooper legion under the command of the Dark Lord of the Sith Darth Vader during the Imperial Era. The legion predated the Galactic Empire, its origins dating back to the Clone Wars of the late Republic Era when the 501st was an elite military battalion of clone troopers in the Grand Army of the Galactic Republic. Under the leadership of Jedi General Anakin Skywalker, Jedi Commander Ahsoka Tano, and Clone Commander CT-7567 "Rex," the 501st fought against the Separatist Droid Army of the Confederacy of Independent Systems. Throughout the conflict, the soldiers of the 501st were known for their courage, unconventional tactics, and loyalty to the Republic.