Event · M31

Isstvan V Dropsite Massacre

The Isstvan V Dropsite Massacre was a battle of the Horus Heresy fought in the Urgall Depression on Isstvan V in 006.M31. The world’s name is also rendered Istvaan V in older Imperial records, and the engagement is remembered as the Drop Site Massacre. Four Space Marine Legions presumed loyal to the Emperor turned without warning upon three loyalist Legions sent to relieve what those Legions believed was a besieged Warmaster, in what stands as one of the largest single acts of betrayal in the history of the Imperium. The massacre followed directly from the atrocity at Isstvan III, where Horus Lupercal, Warmaster of the Great Crusade, had revealed his rebellion against the Emperor by ordering a virus-bombing of his own loyalist troops on that world’s surface. Survivors of the destroyer escort Eisenstein carried warning of the atrocity to Terra, and Rogal Dorn, Praetorian of Terra, ordered a relief force to the Isstvan system to bring Horus to account. Horus withdrew his remaining forces into the Urgall Depression on Isstvan V, anticipating the punitive fleet and preparing his Legions to destroy it. The relief force was led by three primarchs — Ferrus Manus of the Iron Hands, Vulkan of the Salamanders, and Corvus Corax of the Raven Guard — accompanied by smaller detachments drawn from other Legions. On landing in the depression, they assaulted the Legions that had already declared openly for Horus at Isstvan III: the Sons of Horus, World Eaters, Death Guard, and Emperor’s Children. As that fighting turned in the loyalists’ favour, four further Legions arrived under Imperial colours as ostensible reinforcements — the Iron Warriors, Night Lords, Alpha Legion, and Word Bearers — and instead fell upon the loyalist rear, closing the trap. Konrad Curze led the Night Lords in person in this second wave, revealing his treachery as his Legion fell upon the Raven Guard, Salamanders and Iron Hands, and one account records that he fought Corax alongside Lorgar; Sevatar, his First Captain, fought in the same wave. Ferrus Manus was killed in single combat with Fulgrim, primarch of the Emperor’s Children, during the massacre. The Iron Hands, Salamanders, and Raven Guard were reduced to a fraction of their former strength, and their survivors became known collectively as the Shattered Legions. Vulkan and Corax each escaped the depression with remnants of their commands — Corax’s flight leading in time to the Raven Guard’s reconstitution as a fighting force — while the destruction of the loyalist relief effort removed the last significant obstacle to Horus’s advance on Terra. In the Heresy’s aftermath, Imperial forces returned to Isstvan V during the Scouring, in the campaign later recorded as Operation Carthage, the second pacification of Isstvan V, to reduce the fortifications the Traitor Legions had left behind. The name Isstvan V has since come to denote the massacre itself rather than the world alone, standing in later Imperial memory as the moment at which the rebellion first disclosed at Isstvan III became an open and irrevocable war against the Emperor. The order of battle for the Drop Site Massacre names First Captain Calas Typhon among the traitor commanders, listed alongside his primarch Mortarion. No separate personal action of Typhon’s on the Urgall Depression is recorded in that order of battle. When Fulgrim killed Ferrus Manus, that act was the signal for Angron and Mortarion to lead their Legions into the attack on the Urgall Depression. At Isstvan V, during the Dropsite Massacre of 006.M31, Fulgrim, primarch of the Emperor’s Children, was by then secretly possessed by a daemon. When he quit the field, command of the Legion’s forces on the planet passed jointly to Lord Commander Eidolon and to Lucius. Vulkan led the Salamanders in the Ignis Sector of the Urgall Depression against the Death Guard under Mortarion. Earlier, a message from Vulkan urging caution had been blocked when Alpha Legion operatives sabotaged an astropathic relay station, and at a council of war aboard the Ferrum, Ferrus Manus persuaded Vulkan and Corax to attack at once. When the second wave turned on the loyalists, Vulkan argued for digging in around the Salamanders’ dropships while Corax ordered a retreat, and at the climax of the massacre Iron Warriors under Forrix fired an artillery barrage that included tactical nuclear missiles on Vulkan’s position. Some 83,000 Salamanders, with Solar Auxilia and Mechanicum troops, died in the Ignis Sector. Accounts of Vulkan’s own fate differ; one records that he survived through his nature as a Perpetual, able to regenerate from any wound, and was taken prisoner by Konrad Curze aboard the Night Lords flagship Nightfall. Perturabo, primarch of the Iron Warriors, was present at the massacre with his Legion in the second wave. The Iron Warriors had come to the Warmaster’s side after Perturabo’s purge of Olympia, when Horus praised the act that the primarch believed the Emperor would never forgive. Accounts differ on how Perturabo came by Forgebreaker, the thunder hammer of Ferrus Manus: one records it as Horus’s gift after the massacre, sealing their pact, another as a gift from Fulgrim. After the battle Horus dispatched the Iron Warriors against the Imperial Fists Retribution Fleet, an order that led to the Battle of Phall. Corvus Corax brought the Raven Guard into the relief force, and aboard the Ferrum he was persuaded by Ferrus Manus, alongside Vulkan, to commit his legion to an immediate assault rather than wait. When the second wave broke and turned upon its allies, Corax ordered his own warriors to retreat, but in the chaos of withdrawal he came upon Lorgar and drove his lightning claws through the Word Bearers primarch, pinning him and preparing a killing stroke before Konrad Curze fell upon him and beat him back, saving Lorgar’s life. Grievously wounded, Corax led perhaps three thousand surviving Raven Guard into the hills above the dropsite; one account records ninety-eight days of guerrilla fighting on Isstvan V before Branne Nev’s rescue brought them off world, an episode remembered as Raven’s Flight. Given the distance to Isstvan, Ferrus Manus had taken only the Legion’s fastest ships and came to the Urgall Depression with his veteran companies; one account credits him with overall command of the assault’s first wave. He led the central thrust in person, advancing beside First Captain Gabriel Santar at the head of some ten companies of Morlock Terminators, with Vulkan’s Salamanders on the left flank and Corax’s Raven Guard on the right, and the bulk of the Legion’s Terminators and Dreadnoughts following in his wake. When the Traitor line buckled, Ferrus disregarded his brothers’ counsel to fall back and reorganise at the drop site, driving on after the retreating Emperor’s Children in search of Fulgrim himself; his Morlocks cut through the defenders and closed with the Phoenix Guard. It was Fulgrim who showed him the fresh legions massing on the northern ridge, moments before that second wave opened fire on the Raven Guard and Salamanders and the World Eaters, Sons of Horus and Death Guard fell upon the isolated Iron Hands veterans. The primarchs then fought one another directly; one account has Ferrus wielding the sword Fireblade against Fulgrim’s Forgebreaker. Wounded, Fulgrim drew the daemon-bound blade taken from the Laer temple and struck off Ferrus’s head, then, grief-stricken at the act, surrendered himself to the daemon within the sword; thus possessed, he carried the head to Horus. No body was ever recovered, and many Iron Hands have refused to accept their primarch’s death, one legend holding that his remains were borne to Mars and restored there, a claim the Legion itself disavows. His veterans were all but annihilated at his side, only a handful escaping the Depression alive. In the aftermath of the massacre Fabius Bile of the Emperor’s Children remained on Isstvan V long enough to trawl the ancient choral conclaves of the warsingers, scavenging sonic and vocal lore left by those adepts of the Isstvan System. The knowledge he took from that ruined world fed later experiments and the sonic weapon-traditions of his Legion, distinct from the Drop Site fighting itself.

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