M31

Year	Event	Source
	Roboute Guilliman compiles the first Codex Astartes, which lays down the new organizational doctrine for Space Marine chapters.
012.M31	Scouring of Isstvan III. Warmaster Horus, with 4 other traitor Legions, virus bombs Isstvan III to supress a minor rebellion. Frigate Einstein escape with news of Horus' corrupt activities.
013.M31	Horus Heresy. Seven legions Legion sent against Horus, but four defect to his side and three are destroyed. Marine fight Marine in battles across the Galaxy.	Codex: Space Marines 3rd ed
014.M31	Siege of Earth. Horus lays siege to the Emperor's Palace. The Emperor teleports onboard Horus' battle barge. Sanguineous killed. Horus mortally wounded. Emperor wounded, and placed in the Golden Throne.	WD161
014-021.M31	Great Scouring. Rebel forces throughout the galaxy are quelled. Chaos forces retreat into the Eye of Terror.
021.M31	Second Founding. Marine Legions broken into chapters. 23 new chapters created. Grey Knights secretly created.
084.M31	Jaghatai Khan disappears while fighting Dark Eldar on Corusil V, near the Maelstrom. Presumably he pursued a Dark Eldar Lord through an alien portal that led into the dimension occupied by the Dark Eldar (Commoragh?).
356-372.M31	Vindicator created during third Rothern I pacification of the Great Heresy.	WD231
c 781.M31	The first Black Crusade. The First Battle of Cadia.	Codex: Chaos Space Marines 3
893.M31	Scribe First Order Wendel Voss records the Cleansing of Laeran in which the alien Laer are wiped out by the Emperor's Children led by Fulgrim.	WD255

M30	Timeline	M32