Second Founding
Template:SMPort The Second Founding, of Space Marine Chapters, occurred after the Horus Heresy, in 021.M31. This Founding involved the division of the existing Space Marine Legions into the smaller, autonomous Chapters the Space Marines are now organized into - as decreed by the new Codex Astartes, created by the Ultramarines' Primarch, Roboute Guilliman.
The remaining loyal Legions were divided into smaller Chapters - one chapter maintained their parent Legion's original name, symbol and colors, 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, forming new genetic lines.
Because the 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 chapters created after that initial split.
It is unknown how many Successor Chapters were created - some chapters in the past ten thousand years have doubtless been since destroyed, leaving no records of their histories. Other Second Founding Chapters have been lost in more recent times and their names are all that remain of them. Some survive to this day, the proud inheritors of their Legion's histories and the traditions of their Primarch.
Some Legions, such as the Ultramarines could be divided into many new Chapters; others produced relatively few. The Salamanders, consisting of only 7 Companies at the end of the Heresy, produced no recorded successors in the second founding at all. The division of the Space Wolves Legion produced only one additional chapter known as the Wolf Brothers. It is possible that certain Chapters that are not commonly attributed as descendants of any of the Space Marine Legions were created in the Second Founding.
Some sources (such as 2nd edition's Ultramarines codex) have stated that the Grey Knights were the first of chapters created during the Second Founding. They are an exception among the other second founding chapters in that they have no antecedents, their gene-seed engineered from unknown sources. Their creation is unrecorded, and even their inclusion in the second founding is debatable.
List of Second Founding Chapters
Below is a list of confirmed 2nd Founding chapters with the sources.