The Second Founding of the Space Marines occurred seven standard years after the end of the Horus Heresy, in the early 31st Millennium. This Founding involved the division of the existing Loyalist Space Marine Legions into the far smaller, 1,000-man autonomous Chapters of the Space Marines as decreed by the new Codex Astartes, written by the Ultramarines' Primarch, Roboute Guilliman. The remaining Loyalist Space Marine Legions were divided into smaller Successor Chapters - one Chapter maintained their parent Legion's original name, badge and colours, while the remaining Chapters took new names and heraldry. These original Chapters are known as the Second Founding Chapters. Each Second Founding Chapter initially shared their parent Legion's gene-seed - subsequently each Chapter's gene-seed was isolated by the Adeptus Mechanicus, forming new genetic lines. Because the Space Marines that made up each of the Second Founding Chapters originated from one of the Legions that first served the Emperor, the Chapters that were created were called Successor Chapters, a title not given to later Chapters of the many subsequent Foundings that have been carried out by the Imperium after that initial split to keep the number of extant Chapters at around 1,000. It is unknown how many Successor Chapters were created - some Second Founding Chapters in the past 10,000 years have been destroyed, leaving no records of their histories in the often incomplete Imperial archives of the Adeptus Administratum. Other Second Founding Chapters have been lost in more recent times and their names in the records of the fallen heroes of the Imperium are all that remain of them. Some survive to this day, the proud inheritors of their Legions' histories and the traditions of their Primarch. The Grey Knights, the elite Space Marine Chapter that serves as the Chamber Militant of the Ordo Malleus of the Inquisition, was secretly created during the Second Founding, the source of its gene-seedunknown. It is possible that the Raptors, the Silver Skulls and other Chapters were established in the Second Founding.

Select Second Founding Successor Chapters

Sources

• Codex: Angels of Death (2nd Edition), p. 7
• Codex: Black Templars (4th Edition), p. 6
• Codex: Blood Angels (5th Edition), p. 54
• Codex: Blood Angels (3rd Edition)
• Codex: Dark Angels (5th Edition), pp. 10, 73-75
• Codex: Dark Angels (3rd Edition, 2nd Release)
• Codex: Dark Angels (3rd Edition), p. 14
• Codex: Space Marines (5th Edition), pp. 7-8
• Codex: Space Marines (4th Edition), pp. 22-47
• Codex: Space Wolves (5th Edition), p. 9
• Codex: Space Wolves (2nd Edition), p. 9
• Codex: Ultramarines (2nd Edition), pp. 9-10
• Deathwatch: Honour the Chapter (RPG), pp. 9-16, 58-88, 103-105, 106, 109, 111
• Deathwatch: Rites of Battle (RPG), p. 53, 55-58, 60-64, 66
• Index Astartes I, "Codex Astartes: The Holy Tome of the Space Marines," by Rick Priestley & Andy Chambers, pp. 12-13
• Warhammer 40K Compendium (1st Edition), p. 34
• White Dwarf 287 (UK), "Horus Heresy: Sabertooth CCG," p. 86
• White Dwarf 258 (UK), "Index Astartes First Founding: Wolves of Fenris"
• White Dwarf 248 (UK), "Index Astartes First Founding: Promethean Warriors - The Salamanders Space Marine Chapter," p. 76
• White Dwarf 177 (UK), "Golden Demon Space Marine Chapter Design Competition", p. 30
• Age of Darkness (Anthology) edited by Christian Dunn, "Rules of Engagement" by Graham McNeill
• Battle of the Fang (Novel) by Chris Wraight
• Legion of the Damned (Novel) by Rob Sanders