The conflict known as the Battle of Atraken, also referred to as the Atraken campaign or the disaster of Atraken, stands as one of the protracted engagements within the Clone Wars. This battle culminated in the utter ruin of the planet, rendering it unfit for habitation.
Atraken, previously abundant in doonium, transformed into a battleground when CIS protectionist troops declined to cede control of the mining enterprise situated there. Having fortified themselves within the planet's crust for approximately a year, the Separatists unleashed biochemical agents in an effort to repel the Galactic Republic's clone troopers. This action tragically resulted in the deaths of hundreds of thousands of civilians as the toxins permeated a significant portion of the planet's water systems and ecosystems.
Atraken, as one of the initial battlegrounds of the war, endured nearly a year of constant combat. For much of this time, the two opposing sides found themselves in a state of deadlock. The planet's remote location relative to the Corellian Trade Spine impeded the Republic's resupply operations, yet the advancement of Operation Katabatic led to the defeat of the Separatist's droid armies.
Despite the accomplishment of Operation Katabatic signifying triumph for the Republic forces and depriving the Separatists of access to the crucial shipbuilding ore, the Battle of Atraken represented a catastrophe for the one million inhabitants of the colony world. It's estimated that around 90% of the planet's population were either poisoned, displaced from their homes, or lost their lives during the fighting. Those with the means to do so escaped to neighboring planets, while others were thought to have sought refuge on Trilos, the only moon of Atraken possessing a breathable atmosphere.
The Battle of Atraken also demonstrated to the Republic the impossibility of conducting a "clean" war.