Castigation of Ziphon

The Castigation of Ziphon was a lamentable campaign carried out by the Obsidian Blades Space Marine Chapter in the early centuries following their inception. While conducting a xenocidal purge upon the former Imperial world of Ziphon, which was occupied by the upstart Tau, they soon encountered a more insidious threat in the form of the Alpha Legion Traitor Legion and their nefarious agents, which nearly saw their Chapter destroyed.

History
While executing a campaign against the Tau occupiers of the planet Ziphon, the Obsidian Blades were deceived, assuming their opponents just the xenos invaders, they executed their battle plan with little thought to the local population, and what may have occurred to them since the Tau's occupation. In the Tau's presence, faith in the God-Emperor had weakened, and in its absence, heresy had festered.

In the time since the Tau occupation, agents of the Alpha Legion had infiltrated the oppressed human population, and spread dissent and chaos. When the Obsidian Blades made planet fall at full chapter strength they executed their campaign without thought to the potential betrayal of the local population. When the Obsidian Blades besieged the planetary capital, the fighting was fierce, entrenched Tau forces proffered impressive defensive capabilities, and had the supplies to last potentially years. Their fall came from the incited and dissident human population of the city, who rose up against their Tau overlords, led in secret by the Alpha Legion insurrectionists. When the Siege was broken, dismantled from within by the ferocious hordes of imperial citizens, the Obsidian Blades expected to be welcomed into the city as heroes and saviours. Instead, the moment their forces relocated inside the city, they were turned upon by the blood drunk and heretical imperial citizens. Crushed by the massed throngs of now chaos cultists, the beleaguered and exhausted remains of the Obsidian blades were ruthlessly torn apart by concentrated gun fire and ripped limb from limb by hundreds of cultists. Tanks were swarmed and destroyed, explosives strapped to their undercarriages, left immobile and desecrated.

Those few Marines that managed to evade or fight free of the hordes retreated into the bowls of the Hive city, to survive and continue fighting a war in the shadows. Months went by as the marines fought a more and more desperate guerilla war with the cities inhabitants, trying to find some way to contact their fleet in orbit that not send them reinforcements for fear of the anti-aircraft guns that armed the city and not possessing enough troops and armour to attempt another siege. Their only hope was to disable the anti-aircraft guns and signal to the fleet to enact a retreat to orbit.

Months of secrecy and desperation dragged by, as the capital fell further and further into darkness. Finally, they were able to breach the Imperial palace, and disable the anti-air guns that protected the cities skies, and send a message to their ships in orbit. Their fury unleashed, the Obsidian blades aerial support descended upon the city in a wave of fire and death. The remaining marines in the city rallied to the defence gun control deck, making their stand until they could be evacuated, for once they were off world, the whole world would be bombed from orbit. As they were evacuated on transports to orbit, the city burned, and their vengeance was exacted.

Only two hundred Marines escaped that campaign, almost all of their armour was wrecked, and gene-seed was unrecoverable, the chapter's future almost doomed then and there.