The Legion's soldiers were mainly defectors from the Republic Volunteer Army, an organization of non- clone forces that fought for the Galactic Republic. It was led by Tao Vander, a general who defected from the Grand Army of the Republic a few weeks after the Battle of Geonosis in 22 BBY.
It was the largest volunteer legion in the Separatist Droid Army, having around 750,000 personnel, organized in 250 battalions, which themselves were divided into nine corps-sized formations. The Human Legion was a volunteer unit of Human soldiers and officers serving the Confederacy of Independent Systems.
