ca. 900.M30 Establishment of the Temple of the Saviour Emperor - A highly decorated Imperial Army officer takes the name "Fatidicus," meaning "prophet," and secretly establishes the Temple of the Saviour Emperor on Terra which worships the Emperor of Mankind as the God of Humanity in violation of the atheistic doctrines of the Imperial Truth. Via the Imperial Army, and with the aid of other cults of Emperor-worship such as the Lectitio Divinitatus, his teachings will eventually spread across the entire newborn Imperium of Man.
ca. 900s.M30 Assault on Dulan - As the Space Marine Legions pushed back the frontiers of the Imperium, each Primarch strove to excel in the eyes of the Emperor and none more so than Leman Russ, Primarch of the Space Wolves. Only Horus and Lion El'Jonson could claim more victories than Russ and this was a constant frustration for him. It was on the world of Dulan where the Space Wolves were fighting alongside the Dark Angels that matters came to a head. The Tyrant of Duran had personally insulted the Emperor, sacrificing thousands of Imperial envoys to his patron daemon, and both Russ and Jonson desired the honour of slaying this Heretic. The Tyrant Durath insulted Russ, causing him to demand the right to lead the attack on the fortress. Johnson ignored him and led his own carefully-planned attack instead, killing the Tyrant personally. After the battle Russ confronted and attacked Johnson, and the two duelled for a solar day and a night. Russ eventually stopped attacking, seeing the humour of the situation, at which point Johnson knocked him unconscious. Now The Lion considered his honour to be satisfied. The prostrate Russ was carried from the fortress by his men and, when he regained consciousness, the Dark Angels had already departed to fight in the Alisore Campaign. Russ swore he would avenge the stain on his honour and, to this day, whenever the Space Wolves and Dark Angels meet, one of their number is called upon to refight the duel of their Primarchs in order that honour may be satisfied.
ca. 900s.M30 Compliance of Tarsis This was an Imperial Compliance action carried out by the Ultramarines Legion upon the world of Tarsis against unknown assailants. During the assault, the Primarch Roboute Guilliman was attacked by a mysterious assailant, but was saved by a native soldier of this world. In a supreme display of humility, Guilliman bent his knee before the soldier and vowed a warrior's oath that should his world ever need aid, then the Ultramarines would answer the call. A temple within the capital city of Erebus displayed the Tarsis Frescoe, a mosaic of enormous proportions painted by an unknown artist that covered the walls, ceiling and even the floor, treating the entire chamber like a canvas. This fresco displayed the events that had occurred during the Great Crusade. In gratitude to Guilliman and the Ultramarines, the planet renamed itself Tarsis Ultra in honour of its saviours.
ca. 900s.M30 Shi'Hu'Gal Purge - The Night Lords, supported by the Titan Legions Legio Vulcanum I ("Dark Fire") and Legio Vulcanum II, carried out the infamous xenocidal purge of the Shi'Hu'Gal Dominion during the Great Crusade; this was a campaign of such fury and viciousness it remains a legend of this bygone era, even after the far greater death and destruction caused by Horus' betrayal of the Emperor.
ca. 900s.M30 Compliance of Tethonus - The Luna Wolves Legion fought against an unidentified xenos-adversary whose identity is not recorded in existing Imperial records while bringing the world of Tethonus into Imperial Compliance. This Compliance action was a long siege of the xenos fortress-states on Tethonus. Horus had tasked the masters of the Forge World of Diamat to create continental Ordinatii siege machines; vast artillery pieces that could devastate the most powerful fortifications. But the war machines took much longer for the forge masters to complete than planned. By the time they were finished, the campaign on Tethonus had been over for over a standard year and a half, and Horus had moved on to other conquests. So the weapons were put into a depot on Diamat against the day when he would come to claim them. Fifty standard years later, Horus would reveal his perfidy at Istvaan III, and would send raiding forces to claim these siege engines for later use in his attempt to overthrow the Emperor of Mankind.
ca. 900s.M30 Assault on Dahinta - On the world of Dahinta, the Luna Wolves Legion fought against a race of self-aware machines called the Overseers, who were led by the artificial general intelligence known as the Archdroid. One of the Emperor's longest-standing commands was that no sentient machines could be allowed to exist, for they had nearly caused the extinction of Mankind when they had rebelled against their Human overseers during the Dark Age of Technology. Despite heavy casualties amongst the Astartes, the thinking machines were wiped from the face of Dahinta by the savagery of the Luna Wolves. Only after the campaign had ended was the full truth learned: the Overseers had been created by a vanished offshoot of humanity that had settled Dahinta, perhaps during the Age of Technology. The Overseers had cared for their lost masters' crumbling cities long after they had become extinct or left their homeworld behind.
ca. 900s.M30 Compliance of Five-Twenty-Nine - This was an Imperial Compliance action carried out by the Alpha Legion against an adversary of unknown origin upon the world designated Five-Twenty-Nine.
ca. 900s.M30 Compliance of Fernius Worlds - This was an Imperial Compliance action carried out jointly by the Alpha Legion and an Imperial Army sentry force comprised of the Geno Seven-Sixty Spartocid. The Seven-Sixty were a well-drilled, gene-engineered regiment and did not spook easily. They played an instrumental role during the Compliance of the Ferinus Worlds.
ca. 900s.M30 Compliance of Thorium Abominiplex - This was an Imperial Compliance action that was carried out jointly by both the Alpha Legion and Death Guard Legion against an unrecorded adversary.
ca. 900s.M30 Xenocide of Kamenka Troika - This was a campaign of extermination waged in the middle years of the Great Crusade against the barbaric Orks of the Kamenka Troika System. The Emperor had issued the writs of war, commanding the Thousand Sons, the Legio Astorum Titan Legion and a Lifehost of PanPac Eugenians of the Imperial Army to drive that savage race of xenos from the three satellite planets of Kamenka Ulizarna, a world claimed by the Mechanicum of Mars. The savagery of that war, the slaughter and relentless, grinding attrition had left tens of thousands of dead in its wake. The Imperial forces proved victorious after two standard years of fighting and earned a score of honours for their war banners. Victory had been won, but the cost had been high. The Thousand Sons sustained severe losses of 873 battle-brothers of the 5th Fellowship, effectively wiping the 5th out as a functioning unit. This forced Magnus the Red to reduce his Legion from ten Fellowships to the Pesedjet, the nine classic Fellowships of Prosperine antiquity.
902.M30 Subjugation of Kaldorax Aleph - The Iron Warriors 118th and 3rd Grand Battalions undertake the forced subjugation of Kaldorax Aleph, but sustain a high blood price to achieve victory, suffering nearly 65% casualties. However, the Iron Warriors succeed in absolutely crushing the non-Compliant forces of the intransigent world.
903.M30 The Defence of Tranquillity - The Emperor's Children Legion defend a series of ancient crystalline gates claimed by the Imperium in the Dalinite Nebula against an unknown xenos fleet, which emerges from these gates, making rapid Warp translations between them. The III Legion eventually overpowers the xenos and drives them back whence they came.
903.M30 Compliance of 47-10 (Khur) - The Word Bearers successfully bring the world of Khur into Imperial Compliance approximately a Terran century before the events of the Istvaan III Atrocity at the outset of the Horus Heresy. The beautiful planetary capital city of Khur, known as Monarchia, called the "Perfect City" by the Word Bearers, was later built by the people of Khur at the direction and exhortation of the Word Bearers to demonstrate their faith and devotion to the God-Emperor.
Early 900s.M30 Golgothan Slaughter, Siege of Sarum - The first known target to suffer the wrath of the World Eaters Legion after their Primarch Angron took command was the stellar wasteland of the Golgotha Sector, located near the galactic core in the Segmentum Ultima, close to the realspace Warp rift known simply as the Maelstrom. Here, the World Eaters came upon the Sarum Sector, and the Forge World of Sarum, which was being besieged by the Abhuman empire known as the Brotherhood of Ruin who wished to take the Mechanicum's technological secrets for themselves. The World Eaters immediately launched a brutal assault upon the Abhuman army and slaughtered them. The Redjak Cult Mechanicum Tech-priests swore to Angron and his Legion directly many oaths of fealty and entered pacts of mutual protection and support. This provided the World Eaters and their Techmarines with a ready source of resupply and armament far outside the Imperium's inner sphere. The campaign that was to follow would last eleven standard years and see no fewer than 48 worlds and outposts ravaged and destroyed by the World Eaters, and 7 separate, dangerous xenos species, including a branch of the Lacrymole, rendered extinct. The XII Legion's fleet cut a swathe of destruction through the wastes of Golgotha, and even into the Maelstrom itself.