The Beheading was a political coup instigated by Drakan Vangorich, the Grand Master of Assassins of the Officio Assassinorum and newly-elected Lord Protector of the Imperium, who had the entirety of the High Lords of Terra assassinated by his agents in 546.M32. He would then install puppet High Lords and oversee the rebuilding and reconstruction efforts of the Imperium for nearly a standard century, but would become corrupted by ultimate power, degenerating into a mad tyrant. Vangorich would later be forcibly removed from power by a large Space Marine retribution force led by the Imperial Fists as well as the Halo Brethren and Sable Swords Chapters.