Imperial Armored Assault Tanks were a heavier version of the Confederate AAT and were equipped with flamethrowers in the place of laser cannons. They also had an additional anti-personnel weapon in each side's flanks, a longer rear bumper and an additional external seat for a turret gunner behind the commander hatch.
Sometime in or around 19 BBY, during the early stages of the Pacification of Kashyyyk, the Galactic Empire enlisted the aid of Trandoshan mercenaries to assist in the deforestation of the planet's vast jungle. Supplied with Imperial Armored Assault Tanks, the Trandoshans proceeded to burn down large sectors of jungle to make way for Imperial industrialization.
Soon after this process had begun, Clone Force 99 arrived on Kashyyyk with the renegade Jedi Padawan, Gungi, with the intent of returning to Wookiee to his people. After coming across a destroyed Wookiee village, the group spotted a small convoy of two Imperial Armored Assault Tanks and Trandoshan mercenaries with a bounded Wookiee warrior in tow. The group quickly dispatched the Trandoshans and the two Imperial tanks before escaping after freeing the Wookiee prisoner.
Soon after, a larger convoy of Imperial Armored Assault Tanks, clone stormtroopers, and Trandoshans under the command of Commander Babwa Venomor arrived to the scene of the skirmish. The clones recognized the lightsaber cuts on the destroyed tanks, and suggested informing Imperial command to the presence of a Jedi. Venomor instead insisted that he and his mercenaries would be able to eliminate the Jedi first.
The convoy and all of its tanks would soon after be ambushed and destroyed due to the combined efforts of Clone Force 99 and Wookiee warriors.