The 121st Regiment functioned as a mobile armored force within the Grand Army of the Republic throughout the duration of the Clone Wars.
This regiment, known as the 121st, employed vehicles such as HAVw A6 Juggernauts, AT-TE walkers, and AT-AP walkers; these vehicles were identifiable by green markings adorning their armor. The Battle of Herdessa stands out as one of the initial engagements in which the 121st actively fought.