When a massive Ork fleet arrived at Armageddon and began teleporting greenskins onto the surface, many Adeptus Astartes forces rose to meet the opposition!
Via our good friends at Lexicanum
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.
Six weeks after arriving in the Armageddon System, hundreds of Ork Roks smashed into the surface of Armageddon. Millions were killed as Hades Hive – the site of Ghazghkull’s previous defeat – was completely annihilated by an asteroid launched from an orbiting Ork Space Hulk in an act of vengeance against Yarrick. Soon after, wave after wave of Ork landers descended upon the world, and though Imperial Navy fighters and ground defense lasers took a terrible toll upon the invaders there were simply too many incoming Orks to stop. Massive amounts of Orks also besieged Hive Helsreach, where the Black Templars under Reclusiarch Grimaldus made a courageous defense, exacting a heavy toll on the greenskins for any ground taken.
Meanwhile, the true purpose of the descending Ork Roks became apparent. Slowing their descent with powerful force fields, the Roks landed on Armageddon and from them surged not only innumerable Orks but also an endless stream of heavy equipment teleported in directly from orbit. The plan was made possible only by Tellyporta technology designed by Mek Boy Orkimedes, whom Ghazghkull had in his employ. Soon Titans and Gargants beyond number were engaged in the action and took a bitter toll upon both sides in the fighting. In addition Feral Orks, born on the world shortly after the Second War for Armageddon, emerged from the equatorial jungles and spread like wildfire throughout the hives.
Hive Acheron then fell to the Orks without warning, this time captured by treachery from within. It was soon revealed that the infamous war criminal Herman von Strab, the former Governor of Armageddon whose leadership during the Second War had proven so disastrously inept, had overthrown the hive in cooperation with Ghazghkull and now ruled it as its overlord.