The Third Systems Army represented one of the ten total Systems Armies within the structure of the Grand Army of the Republic. Due to the high regard that Jedi Master Obi-Wan Kenobi garnered both within and beyond the Jedi Order, he received a promotion to the military rank of High Jedi General. This appointment placed him as the commanding officer over multiple units belonging to the Galactic Republic as the Clone Wars began.
These units encompassed both the Open Circle Fleet along with the Republic's Third Systems Army, with Clone Marshal Commander Cody from the 7th Sky Corps acting as his second-in-command. As a designated System Army, the Third Systems Army was organized into two Sector Armies and comprised a total of 294,912 clone troopers.