A significant conflict transpired not long before the Battle of Yavin on the world of Kalaan.
The Rebel Alliance had created a sanctuary on this planet, seeking shelter with the Kalaanites inside Kalaan City. After discovering the connection between Kalaan and the Rebellion, Imperial leaders devised a plan to conquer the planet and eliminate any Rebel presence. A fleet consisting of five Imperial-class Star Destroyers entered the planet's orbit and deployed a multitude of landing craft, primarily Sentinel-class landing crafts along with Theta-class AT-AT barges. Emerging from the landing ships was a combined force of AT-AT, AT-AA, AT-ST and AT-PT walkers, supported in combat by 74-Z speeder bikes.
The approaching columns of Imperial armored vehicles advanced upon the city. They were intercepted at a distance by a skirmish line of T1-B hovertanks. The hovertanks were outmatched by the AT-STs and AT-ATs until the heavier T3-B heavy attack tanks moved into position from behind a ridge to provide reinforcement. With combined aerial support from T-47 airspeeders and Y-wing starfighters, the Rebels managed to inflict damage on the Imperial columns.
Despite the temporary delay of the Imperial force, the Rebels' efforts were unsuccessful, and the city was captured by the Empire. TIE/sa bomber squadrons devastated the city, leaving primarily ruins.
Following the battle, stormtrooper units searched through the city's remains. During one of these patrols, a unit from Cattena Squadron had their sergeant killed, at which point Corporal Brenn Tantor assumed command. Captain Beri Tulon, who was surveying the battlefield for talented commanders to use in the BHCI program, noticed Tantor's performance.
Tulon encountered Tantor's squad just as Brenn was tending to his brother Dellis, who had been shot by a Kalaanite. Tulon promoted Brenn to lieutenant and recruited him for the project. Dellis was taken along to receive medical care.
As an outcome of the conflict, the Empire gained control of the planet, constructed a prison, and removed much of its vegetation, intensifying the resentment of the Kalaanite resistance.