The Battle of Shelter Base occurred as a part of the larger Battle of Jabiim during the Clone Wars. This particular engagement signaled the commencement of a disastrous campaign for the forces of the Republic, and resulted in the capture of both an Alpha-class Advanced Recon Commando, specifically Alpha-17, and the Jedi General Obi-Wan Kenobi.
For almost a month, the Republic's military, commanded by Obi-Wan Kenobi, relentlessly attacked the Jabiimi defensive lines scattered across the war zone. By the twentieth day of fighting, they were successfully seizing multiple defensive positions each week. This strategic capture of Jabiimi outposts was part of a larger strategy conceived by the Confederacy of Independent Systems and the Jabiimi, designed to draw the bulk of the Republic's troops away from Shelter Base, which served as the primary operational hub for the stationed Republic forces.
Due to their communications being compromised by water damage and the fact that they were at least a full day's travel from Shelter Base, the Jedi came to the realization that they had walked into an ambush. Shelter Base then came under attack by a large force of Nimbus commandos and battle droids from the Confederacy. Catching the base defenders completely off guard, a missile fired from a hailfire droid tank easily destroyed one of the few AT-AT walkers that were stationed at the base. The ensuing explosion also resulted in the deaths of numerous clone troopers and the Jedi General Rallcema Bylissura.
The attack was overwhelming, resulting in the deaths of many Jedi and clones. Alto Stratus, the leader of the Jabiimi, personally defeated Sana-Jis Ilowa using his vibroblade while she was attempting to use the Force to move an AT-TE that had become stuck in the mud. Following this, he and his forces proceeded to cause widespread chaos among the Republic's ranks. However, the timely arrival of Obi-Wan, Alpha-17, and Anakin Skywalker, along with a large number of their troops, changed the tide of battle, as they attacked the flanks and rear of the enemy forces.
After a brief confrontation with Skywalker, Stratus ordered a retreat to his main force, leading to a general retreat of the Confederacy forces. Utilizing their remaining walker to bombard the Separatist's artillery droids, the Republic easily repelled the retreating enemy. The carnage only came to an end when a squad of Nimbus commandos detonated explosives on the forward leg of the AT-AT, causing it to collapse and trigger a massive explosion. Obi-Wan, A-17, and Jedi Master Sirrus (the master of Aubrie Wyn) boarded the damaged walker in an attempt to save any surviving crew members trapped inside. However, the walker then exploded violently, leading to the assumption that all three had been killed in the blast. Sirrus did die.
As a result of the intense fighting, Shelter Base was left in ruins, leaving Cobalt Station as the Republic forces' most fortified position on Jabiim. Anakin Skywalker and the other master-less Padawans regrouped and headed towards Cobalt Station with the remaining soldiers. Meanwhile, Jedi General [Norcuna]'s troops were annihilated near the city of Choal, leaving Jedi Knight Leska as the highest-ranking officer present on Jabiim.