The conflict known as the Battle of Brentaal IV, sometimes shortened to just the Battle of Brentaal, took place in 22 BBY. The Galactic Republic learned that a Separatist base would be vulnerable for a short period, presenting an opportunity. They also discovered that the planet was planning to join the Confederacy. The planet Brentaal IV was strategically important because it was a key point on the Perlemian Trade Route, which connected the Core Worlds and the Tion Cluster. Control of this planet was considered essential for the war effort. To secure it, the Republic dispatched a force led by Jedi Master Plo Koon, who remained in orbit. This force included four Jedi and a substantial number of clone troopers and various ground and air vehicles, which was expected to be sufficient.
The intelligence turned out to be inaccurate, as the Separatist base was active and prepared. A local clan leader named Shogar Tok controlled the Separatist forces and had successfully instigated a revolt on Brentaal IV, leading the planet to align itself with the Confederacy of Independent Systems. A large-scale ground battle erupted, with Republic and Separatist troops engaging in repeated attacks, retreats, and regroupings. As the Separatists gained the upper hand, Jedi Master Shon Kon Ray, who was leading the air forces, contacted Plo Koon. Overwhelmed by the enemy, Shon Kon Ray recommended a complete withdrawal. Before the transmission could be completed, his ship was destroyed, resulting in his death and the deaths of his troops.
Jedi Master Shaak Ti, still hopeful for victory, informed Plo Koon of her plan to rally the Republic troops at the fortress for a final assault. The number of soldiers who gathered at the fortress entrance highlighted the slim chances of success. Only a handful of troopers managed to meet Shaak Ti at the sewer entrance. Together, they determined that the Republic's best option was to destroy the fortress's ion cannon batteries and shield generators, allowing for an airship bombing run to devastate the enemy.
As Master Ti's team entered the fortress, they discovered its true nature: a prison. The fighting on the surface had triggered a mass escape. Realizing the need for reinforcements, Master Ti promised the prisoners their freedom in exchange for their help in destroying the fortress. This group included Jedi Knight Quinlan Vos, who had been estranged from the Jedi Council for years; Sagoro Autem, a former Senate Guard turned rogue; and a criminal named Lyshaa, who was imprisoned on Brentaal IV. Lyshaa was also revealed to be responsible for the death of Ti's former Padawan, Fe Sun.
The team advanced through the fortress until they reached a point where they had to split up. Quinlan Vos and Autem were assigned to disable the cannons, the sole remaining clone trooper was tasked with destroying the shield generators, and Master Ti and Lyshaa set out to capture Shogar Tok.
The team responsible for the guns was delayed by a patrolling guard unit, leading to a brief firefight before they feigned surrender. Quinlan Vos then used his Force abilities to turn the situation around, sabotaging the guns and rendering them useless. The clone trooper targeting the shields was severely wounded by a grenade launcher but managed to set his rifle to self-destruct, successfully destroying the shield generator.
Master Ti decided to use Lyshaa to seduce Shogar Tok. However, Lyshaa ultimately betrayed Master Ti, shooting her. Just when all seemed lost, Master Ti regained consciousness and killed Shogar Tok. She spared the treasonous Lyshaa, who perished shortly after in a lightstorm chamber while attempting to escape.
A clone trooper who had fought in the battle later participated in an attack on Tirahnn. During that battle, the Clawdite Separatist spy Braxus Lyn disguised herself as Jedi Master Ezar Elasra to free the captured Separatist commander Zolghast. Based on Quinlan Vos's actions during the Battle of Brentaal IV, the trooper suspected that Elasra had also betrayed the Republic. Consequently, he dispatched a team of Republic agents to locate Zolghast and the disguised Elasra.