Adeptus Mechanicus - M30-M31 Dawn of the Imperium: Great Crusade (798.M30-005.M31) - The Emperor leads the massive Great Crusade outwards from Terra, with the purpose of reuniting the hundreds of thousands of lost worlds scattered across the galaxy. At the fore are the Space Marine Legions, supported by the growing Imperial Army. All are equipped by the factories of Mars. No less important are the Skitarii Legions, the Legio Cybernetica, the Legio Titanicus, and the Imperial Knights that join the expedition. Planet after planet is reconquered and offered the same choice -- bow before the Emperor of Terra or be destroyed. On and on the Expeditionary Fleets push outwards. The Tech-priests often refer to this time as the Great Expansion, for hundreds of Knight Worlds are rediscovered during this period alone.Horus Heresy (005-014.M31) - Like all of the branches of the Imperium, the Mechanicum finds itself rife with corruption during the epic civil war known as the Horus Heresy. Many Forge Worlds and Knight Worlds turn from the Emperor. Indeed, the Fabricator-General of Mars, Kelbor-Hal himself, declares his allegiance to Horus, and so begins the Schism of Mars, a bitterly-fought campaign that mirrors those taking place across the galaxy. Skitarii Legions square off against each other while Titan duels Titan. Those of the Cult Mechanicus that turn to the Chaos Gods are forever after known as the Dark Mechanicum. They are hated and feared in equal measure, for they dare to fuse daemons with the Machine Spirits of their war engines, creating twisted things that mock the Machine God and His true laws of order and reason.Birth of the Adeptus Mechanicus (012.M31) - A long-running political deadlock in the Council of Terra back on the throneworld of the Imperium is finally broken, facilitating the formal establishment of the Imperial Adeptus Mechanicus. The Adeptus Mechanicus is recognised as officially separate and distinct from the corrupted Mechanicum of Mars. Fabricator-General Zagreus Kane is appointed its first High Lord of Terra to serve on the council. Final judgement is enacted upon the captive followers of the Traitor Fabricator-General Kelbor-Hal, who are executed in their thousands. Immediately after, the union of Loyalist Titan Orders, under the umbrella of the Adeptus Titanicus or Collegia Titanica, is formed by the Grand Masters of several major Loyalist Titan Legions, although the future of other loyal former Mechanicum divisions such as the Legio Cybernetica and the regular military forces of the Taghmata remains unclear.The Great Scouring (014-021.M31) - Wars of recrimination follow the Horus Heresy. Led by Roboute Guilliman and the Ultramarines, the Imperial forces fight battle after battle, driving the remaining Traitor armies back until they finally flee, seeking refuge in the Eye of Terror. The Knight Houses, their honour tarnished by the vile deeds of fallen Knights, are especially vehement in their pursuit of battles of vengeance. Recognising the need for systemic change, Guilliman creates the Codex Astartes, and tasks Archmagos Dominus Belisarius Cawl with a secret task that will align the fates of the newly-forged Adeptus Mechanicus and the Space Marines for centuries to come.