In the concluding months of the Clone Wars, Jedi Master Depa Billaba took command of a second battalion following the heavy losses sustained by her original battalion during a battle fought on Haruun Kal. Save for four survivors from Billaba's first battalion who chose to stay and serve under the Jedi Master, the clone trooper contingent of the battalion consisted primarily of very young and inexperienced soldiers. Depa Billaba's second battalion was dispatched to the planets Kardoa, Mygeeto, and ultimately Kaller, where the troopers turned against the two Jedi leaders, resulting in Billaba's death as she gave her life to ensure Dume's survival.
After Master Depa Billaba recovered from her coma, she assumed leadership of her new clone trooper battalion alongside her new Padawan, Caleb Dume (who would later become Kanan Jarrus). Four officers from Billaba's previous battalion, specifically Commander Grey, Captain Styles, Sergeant Soot, and Corporal Big-Mouth, joined the ranks of her newly established battalion. Apart from these four troopers, the battalion was largely composed of less experienced and younger clone troopers who wore plain or green armor, which contrasted with the armor design of the veteran troops.
The battalion received orders to conduct reconnaissance on Kardoa to verify the presence of Separatist forces. As the battalion advanced through several canyons, Billaba divided the unit into five squads to carry out their reconnaissance missions. The battalion was then attacked by battle droids commanded by Colonel Coburn Sear. The battalion successfully drove Sear's forces into retreat from Kardoa. A young trooper, CT-1157, earned a commendation for his bravery and was given the nickname "Stance."
The battalion was subsequently deployed to Mygeeto. Once there, the battalion cleared the southern mesas of battle droids. Billaba, Dume, and several of their officers and troopers found themselves surrounded and pinned down by the battle droids. They were rescued by the Fang fighters of Commander Fenn Rau's Skull Squadron and were able to evacuate the area. While the majority of the battalion was away from the base camp, Billaba, Dume, and Stance were attacked by the Separatist commander, General Grievous, and Colonel Sear. Grey, Styles, and the rest of the battalion returned. Despite Billaba being wounded by Grievous, the battalion managed to force Grievous to withdraw from Mygeeto.
Billaba's second battalion was dispatched to Kaller for what would prove to be its final assignment. Although the battalion had initially only included four soldiers from her previous command, by the time of this final mission, a number of clones who had known Billaba for many years had joined the unit. On Kaller, they engaged in combat with battle droids under the command of General Kleeve, who was eventually compelled to abandon the planet. However, Kaller was once again under siege following the Battle of Coruscant. After Clone Force 99 eliminated a force of droids attacking the battalion, the clones received Order 66 from Supreme Chancellor Palpatine. Every member of Depa Billaba's battalion immediately followed the order, opening fire on Billaba and successfully killing her. Dume managed to escape, fleeing into the surrounding wilderness while the clones pursued him. In the weeks that followed, the battalion continued its search for Dume as a unit of the Galactic Empire.
The sequence of events during the execution of Order 66 differs between "Aftermath" and Kanan 2. In the comic book, the order is executed at night, with Billaba and Dume fighting and killing clones Kaylon, Remo, Big-Mouth, Mixx, and Soot. After her death, Grey commands all clones, including the unit Rostu Squad, to search for Dume.