The clash on Yerbana, also referenced as the Yerbana campaign, unfolded on the planet of Yerbana as part of the Outer Rim Sieges during the Clone Wars' closing year. Clone Marshal Commander CC-2224, alongside Jedi General Obi-Wan Kenobi, led clone troopers from the 212th Attack Battalion in an engagement against the Separatist Alliance's droid armies. This confrontation resulted in substantial Republic casualties, necessitating urgent reinforcements. Consequently, Kenobi received assistance from Anakin Skywalker's 501st Legion clone troopers, leading to the demise of the Separatist commander and his forces, and ultimately, the Republic's victory in securing Yerbana.
During the final months of the Clone Wars in 19 BBY, a conflict between the Galactic Republic and the Confederacy of Independent Systems, the Separatist government initiated a significant offensive across numerous star systems within the Outer Rim Territories. This operation was orchestrated by the Kaleesh General Grievous. In response to these Separatist incursions, the Republic deployed its Jedi Generals away from the Core Worlds to bolster their struggling forces. Therefore, Obi-Wan Kenobi and Anakin Skywalker, leading the clone troopers of the 501st Legion and 212th Attack Battalion, were dispatched to the Outer Rim world of Yerbana in the war's closing days to confront the Separatist forces.
Upon arriving on Yerbana, the clone troopers from both the 501st Legion and 212th Attack Battalion received orders to divide their forces across two fronts on the planet. Kenobi's contingent aimed to liberate a city under Separatist control. However, with Cody and his 212th facing heavy losses and requiring urgent reinforcements, Republic Clone Z-95 Headhunters and Low Altitude Assault Transport/infantry gunships continued aerial engagements against Confederacy droid tri-fighters near Kenobi's front. After the 501st secured victory on their front, Skywalker moved to aid Kenobi and the 212th, who were struggling to advance across a bridge into the occupied city due to Separatist resistance.
The Separatist blockade, composed of B1-series battle droids, B2-series super battle droids, DSD1 dwarf spider droids, Octuptarra tri-droids, Armored Assault Tank Mk Is, and NR-N99 Persuader-class droid enforcers, brought their advance to a halt on the bridge. Cody instructed his troopers to seek cover as the Separatist forces launched explosive attacks on their position. When a projectile nearly killed Cody and destroyed an All Terrain Tactical Enforcer, Kenobi intervened, saving the Clone Commander by deflecting the explosive with his lightsaber. With Kenobi present, he ordered his forces to take cover again, and Cody informed him about their inability to locate the Confederacy's ST-series super tactical droid commander due to the droid's continuous barrage. Despite their stalled progress, Skywalker arrived on the bridge and boldly walked into the open while the droids continued to fire upon the 212th, with the Jedi Knight skillfully dodging the incoming shots.
As he advanced further onto the bridge, an OOM command battle droid identified Skywalker and directed the droid forces to focus their fire on the Jedi Knight, who feigned surrender. During this false surrender, the droid commander contacted the super tactical droid, while Skywalker's astromech droid, R2-D2, informed Clone Captain CT-7567, known as "Rex," and several clone jetpack troopers about the Jedi Knight's plan. As the super tactical droid responded to the OOM command battle droid's call, the droid commander realized that Skywalker was luring them into a trap and ordered his battle droids to open fire. However, Skywalker used the Force to pull the droid leader towards his lightsaber, destroying it. Simultaneously, the clone troopers revealed themselves and launched an attack on the Separatist blockade, forcing the battle droids to retreat as Kenobi's forces advanced from the bridge.
As the battle concluded with a Republic triumph, granting them control of Yerbana, the Jedi received a message on Anakin's subspace frequency "Fulcrum" and were summoned back to their ship. They believed the message was from Saw Gerrera requesting assistance in the siege of Onderon. However, the actual sender was Skywalker's former Padawan, Ahsoka Tano, and Bo-Katan Kryze, sister of the late Duchess Satine Kryze. They sought the Republic's and Jedi's aid in defeating and capturing the rogue Sith Lord Maul.
After meeting with Tano and Kryze aboard a Venator-class Star Destroyer and hearing their request, Kenobi insisted on waiting for the Jedi High Council's approval before committing to the operation. Kryze told Tano she had known this would be a waste of time, but Skywalker had a surprise for his former apprentice, taking her to meet Rex and a unit of the 501st who had repainted their helmets after her facial markings in her honor once they knew she was coming back. The reunion was interrupted, however, by the klaxons going off. When Kenobi arrived at the scene, Skywalker asked if the attack on Mandalore had been approved as the clone troopers ran off to prepare for battle, but the Jedi Master explained that Grievous had attacked Coruscant and the Supreme Chancellor was in danger.
Tano was upset, pointing out that the Jedi playing politics instead of helping people who really needed them was why the general public had lost faith in the Order. Skywalker proposed splitting the 501st and creating a new unit under Tano's command, but Kenobi pointed out that as she was no longer a member of the Republic Military, she could not officially command anyone. Skywalker's solution to this was to promote Rex to Commander so he could lead the new unit, with Tano officially designated as his advisor, which she was amenable to. As Kenobi, Skywalker and their forces headed for the capital of the Republic to stop Grievous, Tano, Rex, and Kryze set out for Mandalore with their forces, beginning a siege to draw Maul out of hiding.
The battle is depicted in the Star Wars: The Clone Wars episode "Old Friends Not Forgotten," which premiered on April 17, 2020.