The Rancor Battalion functioned as a military battalion of clone troopers within the Grand Army of the Republic. This unit included highly skilled Advanced Recon Commandos, such as Clone Commanders Blitz, Colt, Hammer, and Havoc. During the early stages of the Clone Wars, the battalion's ARC troopers were responsible for supervising the training of clone cadets located on the planet of Kamino.
At a minimum, the Rancor Battalion contained four Advanced Recon Commandos: Clone Commanders Blitz, Colt, Hammer, and Havoc. Advanced Recon Force troopers made up the battalion, identifiable by the maroon and grayish-blue markings present on their helmets, with some also displaying maroon lines on their arms. Each ARC trooper customized their individual sets of ARC trooper armor; Colt and Hammer utilized red and gray color schemes, Havoc employed blue markings, and Blitz favored yellow and gray. The Rancor Battalion's members utilized DC-15A blaster rifles, and at least one RPS-6 rocket launcher. Being a battalion in the Grand Army of the Republic, the Rancor Battalion was organized into four companies, each composed of 576 troopers.
During the Clone Wars conflict between the Galactic Republic and the Separatist Alliance, the Rancor Battalion served as a battalion within the Grand Army of the Republic. Prior to the defense of Rishi Station, the Rancor Battalion was stationed on the planet Kamino, where its four Advanced Recon Commandos oversaw the final training stages for clone troopers alongside Jedi General Shaak Ti, Master Chief Bric, and El-Les.
The Rancor Battalion was once again stationed on Kamino and participated in the Battle of Kamino. Clone ARC Commanders Hammer and Havoc took charge of defending the primary hangars located within Tipoca City and commanded other clone troopers, while Clone ARC Commander Colt engaged in combat near the barracks. Blitz, another ARC Commander, led a trio of ARF troopers along the exterior walkways of the city. Ultimately, the Republic forces achieved victory, and members of the Rancor Battalion were present during the subsequent aftermath and cleanup operations. Later, in 20 BBY, following a series of destructive groundquakes that impacted the planet Aleen, a Republic Navy detachment was rerouted from its course to prevent the annexation of the Qiilura system to conduct a humanitarian mission to Aleen to deliver aid and restore their systems.
Within the hangar bay of the Acclamator-class assault ship, there were at least three ARF troopers belonging to the Rancor Battalion, with one of them loading their All Terrain Reconnaissance Transports inside an All Terrain Tactical Enforcer while members of the 104th Battalion boarded LAAT/i gunships. This ARF trooper joined their comrades from the 104th in providing assistance to the Aleena. Protocol droid C-3PO and astromech droid R2-D2, who were involved in aiding the Aleena, were discovered by 104th clone troopers and one of the Rancor Battalion's ARF troopers aboard an AT-RT after they briefly went missing when they fell into the Aleen Underworld. Following the completion of the relief mission, the ARF trooper from the Rancor Battalion loaded their walker into the AT-TE and was transported away.
The initial appearance of the Rancor Battalion occurred in "Clone Cadets," which was the premiere episode of the third season of the animated television series Star Wars: The Clone Wars.