The Kaleesh–Imperial conflict represents a war between the Kaleesh Resistance, led by Bentilais san Sk'ar, and the forces of the Galactic Empire. This struggle extended for more than a decade.
Subsequent to the Huk War, the sacred burial sites of the Kaleesh on the planet Oben were defiled by the Yam'rii. This act spurred the Kaleesh warlord Qymaen jai Sheelal to abandon his employment with the InterGalactic Banking Clan and reassume leadership of the kolkpravis. The IBC then sabotaged Sheelal's shuttle, named the Martyr, resulting in the deaths of seven out of eight Izvoshra, the elite warriors charged with his protection and the execution of his directives, and nearly killing Sheelal himself. Qymaen was later reborn as General Grievous, the Separatist cyborg who would become a central figure in the Clone Wars.
Bentilais san Sk'ar, the sole Izvoshra survivor and a ruler from Kalee's western territories, united the kolkpravis and oversaw the massacre of the Yam'rii on Oben, where he then relocated his people. Following the Clone Wars, the Galactic Empire under Palpatine's command began to target the Kaleesh, motivated by their previous allegiance to the Separatist cause. The Kaleesh Resistance, under the leadership of Bentilais, resisted for over a decade before finally being defeated by Captain Thrawn on Oben.
Thrawn, typically able to decipher his enemies' strategies by studying their art, found himself unable to understand Kaleesh art. Consequently, he leveled Oben using his Star Destroyers, causing extensive losses and effectively ending the rebellion. Sk'ar managed to survive the devastating bombardment from the Imperial fleet. However, he held no animosity towards his foes, admiring their advanced technology and strategies, and believing his people had met their end with dignity.
When approached by Imperial occupation forces led by Captain Rel Bentin, Sk'ar offered either his life or his services. Bentin, intimidated by Sk'ar's imposing stature, brought the Kaleesh before Emperor Palpatine. Despite the Empire's xenophobia towards non-humans, the Emperor was sufficiently impressed by the Kaleesh's bravery and potential, leading him to enlist Sk'ar into the Imperial army.
Subsequently, Sk'ar became a figure of galactic renown, recognized as one of the few non-humans to attain a significant position within the predominantly human Galactic Empire, alongside Grand Admiral Thrawn and the Procurator of Justice Hethrir. Leading an Imperial strike force, Sk'ar initiated a campaign across the Jahilid Drift, conquering numerous worlds and establishing a reputation within the Imperial Military. Simultaneously, the kolkpravis fell under the control of an unidentified_female_kaleesh_leader female Kaleesh who was believed to be the reincarnation of Grievous's deceased soulmate, Ronderu lij Kummar.