Event · M31–M32
Great Scouring
The Great Scouring was the Imperium’s counter-offensive against the Traitor Legions, waged across 015–021.M31 after Horus’s death at Terra. It followed the Horus Heresy, the civil war in which nine Space Marine Legions turned against the Emperor of Mankind, and it set out to purge Chaos-corrupted worlds, reclaim territory seized by the rebels, and drive the surviving Traitor forces into the warp rift known as the Eye of Terror. The offensive began the moment the Siege of Terra ended. A relief fleet led by the Ultramarines primarch Roboute Guilliman broke the Traitor blockade of the Sol System as Horus was slain by the Emperor aboard the Vengeful Spirit, and the rebel host, thrown into disarray, fled the throneworld. Guilliman met the surviving loyalist primarchs — Rogal Dorn, the Lion El’Jonson, Jaghatai Khan, Leman Russ, and Vulkan — amid the ruins of the Imperial Palace, where a dispute arose over strategy: Dorn, the Lion, and Russ favoured an immediate, vengeful pursuit of the fleeing Traitors, while Guilliman argued for consolidating Imperial strength and securing Luna and Mars first. The newly empowered High Lords of Terra backed Guilliman’s approach, though Dorn later broke from the agreed plan and pressed his own campaign of retribution. Luna and Mars were retaken in 014–015.M31, and the years that followed saw fighting spread across the Imperium as loyalist forces pursued the scattered Traitor Legions: the liberation of Molech in 017.M31 and the purging of Isstvan V during Operation Carthage in 018.M31 number among the campaign’s notable actions, alongside the siege of the Iron Warriors’ homeworld of Olympia. First Captain Ezekyle Abaddon of the Sons of Horus led remnants of the rebel host in a fighting retreat alongside Lorgar, Angron, Magnus the Red, Fulgrim, Perturabo, and Mortarion; Konrad Curze was killed during the period, and Alpharius is recorded as having died as well, though accounts of his fate differ. By 021.M31 the bulk of the Traitor Legions had been driven into the Eye of Terror, though Night Lords, Emperor’s Children, and Alpha Legion remnants continued to operate within Imperial space, and large engagements against Traitor holdouts, including the reconquest of Zhao Arkkad, persisted for over a century afterward.
See where Great Scouring occurred on the galactic map in the 41st Millennium.