Mordecai Secundus: Kuneus retaken by chaos

The Thousand Sons did not waste time following their advance north to surround the city of Ur'Ghar. Previously the forces of chaos, led by the Emerald Serpent, had been pursuing a strategy of siege against the city, rather than face the Grey Knights in street fighting, which they rightly judged would likely end in defeat. Now that the Grey Knights had repositioned however, they did not hesitate to launch an assault against the city.

The suddenness of the attack caught the Imperium off balance, and the Adeptus Mechanicus forces had no support in their defence of the city. They fought hard for every street and building, but the Thousand Sons had once again redeployed their most powerful assets using the daemonic power of Astralis. Gradually the streets were reclaimed by the chaos army, and the Mechanicum, rather than face annihilation, abandoned the city by making the hazardous crossing of the Kuneus Traps, a vast lava sea that remained passable to the Mechanicum only by their advanced knowledge of technology and their faith in the Machine God.

Kuneus had once again fallen to the forces of chaos, a strategic setback which Kutuzov knew would reinvigorate the enemy, and risked putting the Imperium on the back foot on Mordecai Secundus.