The Battle of Armatura struck at the very sinew of Ultramar's military might, for Armatura was the great war-world where the Ultramarines trained their aspirants and honed the martial doctrine of the Five Hundred Worlds. To break Armatura was to cripple the Legion's future, and the traitors understood this well.
As the Shadow Crusade raged, the World Eaters and Word Bearers fell upon the war-world in force. Armatura was defended by cadres of Ultramarines cadets and instructors, warriors not yet blooded in true battle, and they faced the full savagery of Angron's berserkers and Lorgar's zealots. The academies and training-grounds, built to forge legionaries, became abattoirs.
The defenders fought with a discipline beyond their years, exacting a bitter price for every hall and rampart, but courage alone could not stem the tide. A generation of Ultramarines aspirants was consumed in the fighting, a wound to the Legion's strength that would be felt for decades to come. When Armatura fell, the traitors had not merely taken a world but had reached into the future of their enemy and torn out a piece of it, leaving the war-world a silent ruin of unfulfilled oaths.