The Siege of Terra

No wound in humanity's history runs deeper than The Siege of Terra, the apocalyptic climax of the Horus Heresy fought in the closing years of the 31st Millennium. For seven years the galaxy had burned as the Warmaster Horus turned half the Space Marine Legions against their father, and now his traitor fleets blackened the skies above mankind's cradle. The long civil war had come home to Terra at last, and upon its outcome hung the fate of the entire species.

The outer defences of the Sol System were drowned in fire before the first drop-ships fell. When the Sons of Horus and their allied traitor Legions made planetfall, they found the Imperial Palace transformed into the mightiest fortress ever raised, its ramparts manned by loyalist Astartes, the countless soldiers of the Imperial Army, the Legio Custodes and the Sisters of Silence. What followed was slaughter beyond reckoning, month upon month of siege-craft, orbital bombardment and butchery across walls choked with the dead.

Bastion by bastion the Palace was broken open. The Iron Warriors ground down defences the Imperial Fists had sworn to hold, daemons walked freely as the veil between worlds thinned, and primarch duelled primarch amid the ruin. Sanguinius of the Blood Angels fell holding a shattered gate, and still the traitors could not force a swift end. At last Horus, sensing the Emperor's hosts closing and his own moment slipping away, lowered the void shields of his flagship in a final act of arrogance, daring his father to come to him.

The Emperor teleported aboard the Vengeful Spirit and confronted the son he had loved above all others. The duel unmade them both: Horus was slain, but only after he struck the Emperor down. Carried back broken beyond healing, the Master of Mankind was bound to the Golden Throne, neither living nor truly dead, and the Imperium he had forged was left to grieve in his shadow for ten thousand years. The fuller account is told in the chronicle of the Siege of Terra.