Created by the Emperor from samples of the Primarchs, the Space Marines are credited with molding the Imperium in the Great Crusade. With their superhuman abilities, they conqured world after world in the name of Mankind. After the Horus Heresy the Space Marine Legions were divided into Chapters, each one numbering roughly 1000 strong. Scouring the galaxy in search of the Alien, Traitor and Mutant, Space Marines remain the most feared warriors of the Emperor.
The vehicles and troops available to the Space Marines are as diverse as the Chapters themselves. Tactical Squads make up the bulk of the force, which in turn are supported by Rhinos and Razorbacks. The elite of the elite, Terminator Squads can advance deep into the enemy nearly impervious to enemy fire, while Assault Marines, equipped with powerful jump packs rain fire from above. Various speeders and bikes can outflank the enemy, before being crushed by the massive weaponry of Devastator Squads, Vindicators, Predators, Whirlwinds, and Land Raiders.
Recently, the Primaris Space Marines have been mass produced thanks to the efforts of Belisarius Cawl, introducing a new generation of warriors to defend the Imperium.
While few in number compared to the Imperial Guard, Space Marines are organized into Chapters, numbering more or less a thousand Battle-brothers as dictated by the Codex Astartes. As the huge Space Marine Legions, who remained loyal were re-organized, a single chapter kept the original name and identity, and the rest of the Legion was split into new Chapters. Twenty-Six Foundings have occurred, creating over 1000 chapters. The names of the most famous Chapters are known by billions across the galaxy and their exploits pass into legend.