The Kayvas Persecution was a xenocidal campaign conducted between the Blood Angels and Alpha Legion Legiones Astartes in 002.M31, during the waning days of the Great Crusade against the remnants of Ork Warlord Urlakk Urruk's greenskin empire of Ullanor.
Many tribes of Orks, scattered and leaderless after the hammerblow they had suffered at Ullanor during the Ullanor Crusade, had fled to the points of the etheric compass – and many had come to rest in the Kayvas Belt, where they carved new outposts out of the drifting, mineral-rich rocks, licked their wounds while they re-armed. The Greenskin xenos soon began to strike out at nearby Imperial star systems and newly Compliant daughter colonies, and it was the duty of the Space Marine Legions to reinforce the lesson of Ullanor again. The Alpha Legion had tracked them to their lair and petitioned the Warmaster Horus for the reinforcements required to prosecute their plan of annihilation, but after the war at the world called Murder and the disastrous engagement with the civilisation known as the Interex, the Luna Wolves had been reluctant to commit ships to Alpharius’ new campaign.
In the end, it was the Blood Angels who agreed to assist their cousins in the XXth Legion, with Sanguinius himself marshalling a sizable intervention to support the efforts of the 88th Expeditionary Fleet. The mission, Alpharius said, would be five standard years in execution. The Angel rejected that premise and promised it would be over in one, and he committed vessels from every active Blood Angels expeditionary fleet to the cause. Sanguinius was proved right -- more or less. Just over thirteen months after the commencement of the Kayvas initiative, the Orks were almost totally annihilated, but like animals backed into a corner they fought harder than they ever had before.
The 88th Expeditionary Fleet took their warships into the Kayvas Belt and vanished from the sensors of the IXth Legion's fleet, leaving the Blood Angels flotilla at the edge of the system to wait. Soon it became clear that the mission Alpharius had been so eager to secure support for was little more than picket duty. First one at a time, then in squadrons and finally in fleets, the Orks began to flee from the Kayvas System. Each time they bolted for open space beyond the mass shadow of the supergiant sun and its asteroid belt, the Blood Angels were waiting for them. Imperial starships and Ork cruisers engaged in deadly games of cat-and-mouse that lasted for weeks on end, threading in and out of the dense dust clouds at the periphery of the star system, mercilessly hunting each other. Mighty vessels clashed again and again, but months of protracted ship-to-ship engagements and naval warfare made the Sons of Baal restless. They had been bred for battles where they could face their foes, not ranged conflicts conducted over huge spans of empty vacuum.
However, the chance to fight blade-to-blade did come. The behaviour patterns of the Ork crews began to change. They eschewed what little animal cunning they had and made mistakes. Instead of showing the brutish slyness they were known for, the xenos exhibited conduct that more closely resembled panic. They would take chances, running the gauntlet of the Blood Angels' blockade when the odds were stacked against them. It was almost as if there were something at their backs that they feared far more than the guns of Sanguinius’ Legion. No one within the IXth Legion knew what the Alpha Legion had done to make the Orks run. All that was certain was that the Alpha Legion had gone dark, only rising to send regular communiqués out to the Blood Angels' blockade fleet that contained little more than a message to "maintain the line."
Finally, Sanguinius tired of Alpharius' evasive manner and sent a frigate in past the outer marker, in defiance of the rules of engagement the two Legions had agreed upon. When the frigate returned weeks later, the crew reported that they had come across no signs of their allies, only the wrecks of Ork vessels and the bodies of dead aliens. The Alpha Legion's 88th Expeditionary Fleet comprised hundreds of warships, and yet no trace of them was sighted. The tempo of the Kayvas campaign had finally reached a terminal pitch. The final remnants of the Ork forces took flight from the belt in a disordered exodus, and perished in the flashes of Lance cannons and torpedo barrages as they crossed the sentry line. At last, the Alpha Legion's starships appeared at the very edge of scanning range, apparently moving in a wall, herding the enemy towards the fringes of the system. The Alpha Legion stated they had fully exterminated the alien infestation in the Kayvas Belt, and were grateful to the Blood Angels for their co-operation. The blockade was finally over, and with the death of the final monolithic Ork wreck at the hands of the Blood Angels fleet, the campaign came to a successful conclusion, though relations between the IXth and XXth Legions remained somewhat strained.
- Fear to Tread (Novel) by James Swallow