Event · M31

Solar War

The Solar War was fought across the Sol System in 014.M31, as Horus Lupercal’s Traitor fleets drove toward Terra in the Horus Heresy’s final campaign. Some accounts trace its opening clashes as far back as 010.M31, when Traitor forces first tested the system’s outer defences. It forced open the approaches to the Throneworld ahead of the Siege of Terra, the assault on the Imperial Palace that followed, and the two campaigns are recorded as sequential phases of a single battle for Terra. With the Emperor withdrawn from active command, Rogal Dorn, Primarch of the Imperial Fists, organised the Sol System’s defence into a series of concentric commands reaching from Pluto and Jupiter, through the blockade of traitor-held Mars, to Mercury and Luna at the Throneworld’s threshold, each combining Imperial Fists, Imperial Army and Mechanicum forces, with First Captain Sigismund holding the outer command. The Alpha Legion’s early strikes, including an uprising at Terra’s Damocles Starport and an assault on Pluto in which Alpharius was reported slain, tested these defences years before the main Traitor armada arrived. Horus’s victory at the Battle of Beta-Garmon in 013.M31 opened his route to Terra, after which Dorn reinforced the system with newly arrived Blood Angels and White Scars in preparation for the final assault. When the Traitor armada translated into the system in 014.M31, Sigismund held Pluto while Jaghatai Khan’s White Scars and Sanguinius’s Blood Angels reinforced the inner defence as the Sons of Horus and their allied Legions pressed inward across hundreds of engagements. Dorn moved his own headquarters from his flagship, the Phalanx, to the Bhab Bastion within the Imperial Palace as Luna and the system’s orbital grid fell to the Traitors. Losses on both sides thinned the fleets before the Traitor forces achieved planetfall, ending the Solar War’s naval phase and opening the ground war recorded as the Siege of Terra. Perturabo commanded one of the two opening thrusts of the main assault. While Horus Aximand led the Sons of Horus against Pluto, the Iron Warriors under Perturabo struck the defences of Uranus and the Elysian Gate, where he oversaw from the Iron Blood an onslaught of more than four thousand vessels against Halbrecht’s Second Sphere fleet, ramming the mass-conveyors Alekto, Megaera and Tilphousia into the loyalist gun-platforms as fire ships and committing the space hulk Daughter of Woe. With the sphere reduced, he loosed pirate and renegade fleets upon Saturn and Neptune and, with Forrix, led the assault on Jupiter, wresting both the Uranus and Jupiter defensive spheres from the Imperial Fists and their allies. The Solar War is remembered as the last occasion on which the Imperium contested Horus at range, before the fighting narrowed to the Imperial Palace, where Mortarion’s Death Guard joined the Traitor assault that culminated in Horus’s duel with the Emperor, in which Sanguinius died and the Emperor was left mortally wounded, ending the Heresy as an organised war. Its cost in ships and lives, borne largely by Dorn’s Imperial Fists and the Imperial Army, shaped the depleted forces that went on to fight the siege proper, making the Solar War and the Siege of Terra the linked opening and closing phases of the final battle for Terra. In the war’s final phase the Knight-Errant Garviel Loken, formerly of the Luna Wolves, received word that the remembrancer Mersadie Oliton urgently needed to speak with Rogal Dorn. Having rebuked Malcador the Sigillite for ordering that prisoners be killed rather than allowed to fall into traitor hands, he crossed the embattled system, rescued Oliton and brought her aboard the Phalanx. She had been unknowingly marked by Maloghurst years earlier, and the daemon Samus emerged through her into the battle-station. Confronting Samus again, Loken relived the Whisperhead Mountains of Sixty-Three Nineteen, where he had first encountered the daemon, and fought in the persona of Cerberus that he had adopted on Isstvan III. Oliton closed the daemon’s portal by throwing herself into the Phalanx’s reactor chamber.

See where Solar War occurred on the galactic map during the Horus Heresy.

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