

There are now around a thousand Chapters in existence, each Chapter ultimately descending from one of the loyalist Legions. Successive foundings over the millennia have created new Chapters.

Each Legion was divided into several autonomous Chapters, which remain the primary unit of the Space Marines to the current day. The Legions which had remained loyal were eventually reorganised according to the dictates of the Codex Astartes, in the event known as the Second Founding. With the rebellion defeated, those Legions which had sided with Horus were driven into the Eye of Terror. In the final battle for control of the future of mankind, Horus was slain by the Emperor. The Crusade, lasting for two centuries, ended with the treachery of one of the Primarchs, Horus, who led at least half of the Legions in a rebellion known as the Horus Heresy against the Emperor. The Legions took part in the Great Crusade, during which the lost Primarchs were rediscovered and given command of their respective Legion. Space Marines battle the forces of Chaos
