The invasion began with a massive Ork fleet arriving in the Armageddon Sector, a fleet which outnumbered the Imperial defenders six to one. Ork Kill Kroozers made suicidal rushes against the Imperial Navy blockade of the planet and despite their skill the Imperial ships found themselves unable to turn back the Orkish tide. Worse yet, monitor stations were warning that three more massive Ork fleets were inbound to the Armageddon system. The combined fleets of Ghazghkull and his allies soon constituted the largest fleet ever to assault a world of the Imperium and Battlefleet Armageddon found itself outnumbered six to one.
As the Ork fleet arrived in the Armageddon System, Imperial forces under Yarrick made frenzied preparations. Forces from the Imperial Guard, Collegia Titanica, Sisters of Battle, and more then twenty Space Marine Chapters reinforced the world, ready to stop the green tide at any cost.