|This article is about the Horus Heresy battle; for the novel, see The Solar War (Novel).|
The Solar War refers to a series of battles fought in the Sol System from 010-014.M31 during the closing stages of the Horus Heresy. The war saw Horus begin his drive on Terra, capital of the Imperium.
With the Emperor preoccupied with the War Within the Webway and Malcador the Sigillite waging the Shadow Wars, it was left with Imperial Fists Primarch Rogal Dorn to oversee the defenses of both Terra and the greater Sol System. The defenses of the Imperial Palace were significantly strengthened, and much of its aesthetic was destroyed in favor of strategic defensibly. Following the Schism of Mars, Kelbor-Hal's Dark Mechanicus was victorious in claiming the Red Planet, but an Imperial blockade trapped the traitors on their own world.
As Horus' forces inched closer to Terra, Dorn organized the defenses of the Sol System into a series of Spheres. Each consisted of not only Imperial Fists forces, but also loyalist Imperial Army and Mechanicum. By the closing phase of the battle Dorn held back most of his Astartes forces on Terra in preparation for the siege.
- The First Sphere was the outermost defensive zone from Pluto to Neptune.[2a] It was commanded by First Captain Sigismund at Pluto.[6a]
- The Second Sphere oversaw Uranus. It was commanded by Fleet Master Halbrecht
- The Third Sphere oversaw the Jupiter region.[6a] It was commanded by Seneschal Efried.
- The Fourth Sphere was commanded by Siege Master Camba Diaz and oversaw the blockade of traitor-occupied Mars[2a][6a] This sphere was the largest of the four outer layers of defense, surpassed only by the Terran sphere.
- The Fifth Sphere was Terra and Luna, overseen by Primarch Rogal Dorn himself.[2a]
For the next several years, the loyalists would counter traitor-instigated uprisings and attempted breakouts by the Dark Mechanicus on Mars.
The Alpha Legion announced its entry into the Solar War by exploding the freighter Primigenia over Terra, killing millions by raining debris. This was accompanied by Alpha Legion organized uprisings at Terra's Damocles Starport and Triton. All of this culminated in the first major battle of the Solar War, the Battle of Pluto. The battle saw the Alpha Legion drive on Pluto, linchpin of the loyalist monitoring of the Sol System. During the battle, a fleet of over 200 Alpha Legion warships assaulted the planet, but after Alpharius himself was seemingly killed by Rogal Dorn the traitors retreated. For several years after, the Imperials continually dealt with attempts by the Dark Mechanicum to break out of their cage around Mars as well as Alpha Legion attacks and Cultist activity.
In 013.M31 Horus won the massive Battle of Beta-Garmon, giving him access to the strategically important route to Terra. It was now certain that Horus would reach the Throneworld, and Dorn increased his defenses with newly arrived Blood Angels and White Scars forces. Dorn and his mostly Human command staff moved their daily headquarters from the Phalanx to the Bhab Bastion of the Imperial Palace. In preparation for Horus' arrival, the Dark Mechanicum on Mars accelerated their breakout attempts and lobbed constant fire from the surface from Mars at a blockade overseen by Captain Camba Diaz. As Horus arrived, Dorn's strategy revolved around holding back and bloodying the traitors as much as possible in the hopes of Roboute Guilliman's inbound reinforcements. The Lord of the Imperial Fists knew his own forces were to meager to hold back the full might of the traitors, but victory would be assured should they wedge Horus' armada between the forces of Terra and Ultramar. Equally, Horus sought to capture Sol and Terra as quickly as possible before Guilliman could arrive at his rear. To save his Astartes for Terra's defense, Dorn withdrew most large space marine contingents to the Throneworld and relied heavily on Legiones Astartes ships crewed mainly by Humans or Imperial Army vessels for the greater Solar System's defenses.
The traitor armada finally arrived at Sol on 0000014.M31, the first day of the first month (Primus). As expected by the loyalists the traitors made their initial assaults on the two Warp gates into the system that allowed for the bypassing of Mandeville Points: the Khthonic Gate at Pluto and the Elysian Gate at Uranus. Near-simultaneously, a Sons of Horus armada under Horus Aximand struck at Pluto while an Iron Warriors fleet under Perturabo assaulted the defenses of Uranus, both engaging the Imperial Fists and Imperial Armada defense fleets under Sigismund and Halbrecht respectively. At the same time, an armada of Sons of Horus, Thousand Sons, Word Bearers, and Dark Mechanicum under Ezekyle Abaddon, Ahzek Ahriman, Zardu Layak, and Sota-Nul respectively moved over the galactic disc, bypassing the initial loyalist defenses and striking down into the upper crest of the defensive spheres. The loyalists had foreseen such a ploy and a force of White Scars under Jubal Khan was ready to meet the traitors. Across the Sol System, hundreds of small engagements erupted to make up a naval battle of titanic proportions. Though the loyalists had the advantage of preparations and large amounts of Orbital Defense Platforms and other armored bastions, the traitors had the luxury of overwhelming numbers and Warp-sorcery. In addition, intelligence provided by the Alpha Legion during their earlier attacks proved critical, with Horus having personally been given a map of all loyalist defenses in the Sol System by Alpharius before he departed the traitor war effort at the Ullanor.
At Pluto commanding from the Frigate Lachrymae, Sigismund decimated the initial waves of primarily traitor Imperial Army vessels which arrived through the Khthonic Gate with not only his fleet but also the Moons of the world, which had now been transformed into gigantic gun-fortresses. However as the traitors arrived in ever-increasing numbers the Sons of Horus finally began to appear, using the ships of their allies as shields to begin to fire back. Soon Horus Aximand himself aboard the Battle Barge Throne of the Underworld translated from the Warp, leading a massive push that saw landings on the fortress-moons. Most of the incoming attacks were by savage Newborn Sons of Horus. One by one, the Newborn Astartes boarded the moons and unleashed Scrap Code that either disabled its defenses or turned them to Horus' cause, resulting in the moons beginning to fire on one another. After the moon of Kerberos fell, Sigismund ordered his fleet retreat. The Sons of Horus pursued, walking into the loyalist trap as Sigismund had loyalist Mechanicum Tech-Priests unleash data-jinns into the power reactor complex of the moon. Kerberos exploded, decimating and scattering the pursuing traitor fleet. At this moment, Sigismund had his fleet turn back around and launched a vicious counterattack on the traitors. In an attempt to reverse the situation, Aximand personally led an assault on the Lachrymae to decapitate the loyalist command. In a clash between the Sons of Horus and Sigismund's Templars, Aximand and Sigismund dueled. Horus Aximand slew the Templar Lieutenant Boreas and wounded Sigismund, but the First Captain of the Imperial Fists was able to teleport away aboard the nearby Frigate Persephone, severing one of Aximand's hands as he retreated. Though wounded, Aximand successfully captured the Lachrymae and organized a counterattack that broke the loyalist fleet at Pluto. Sigismund ordered a withdraw towards Terra, informing Rogal Dorn that the First Sphere had fallen after several days of fighting.[6c]
At Uranus, Perturabo himself from the Iron Blood oversaw a massive traitor onslaught of over 4,000 vessels through the Elysian Gate on Halbrecht's Second Sphere Fleet and orbital defenses. Commanding the Battle Barge Monarch of Fire, Halbrecht's fleet took a ranged approach, sniping from the screen of 27 fortress-moons and hundreds of gun-platforms into the arrival points of Iron Warriors vessels with their Nova Cannons. Enormous space-minefields hindered the traitor fleet, boxing them into these killzones. Perturabo rammed three enormous mass-conveyor vessels known as Alekto, Megaera, and Tilphousia into the loyalist fleet of gun-platforms, using them as Fire Ships and wiping out many of the defenders. With the way to the inner core of Uranus' defenses cleared, Perturabo fielded an enormous Space Hulk known as the Daughter of Woe which unleashed hell on the loyalists with its enormous array of weaponry. One by one the remaining defensive bastions of Uranus fell to the Iron Warriors onslaught, with the firepower from the Daughter of Woe devastating the moons Umbriel, Cordelia, and Oberon. As the Iron Warriors closed the distance with the loyalist defensive bastions, they unleashed transports filled with millions of drug-fueled Gangers, Pirates, Mutants, and Cultists into their bowels. The defending forces, mostly Imperial Army and Servitors, fought valiantly but were overwhelmed by sheer numbers. After a delaying maneuver that bought another 36-hours for the loyalists, Halbrecht ordered a retreat towards Terra. He brought with him the majority of the Second Sphere Fleet, saved in order to bloody the traitors in future engagements. The Second Sphere had fallen.[6d]
With the Second Sphere reduced, there were still thousands of pockets of resistance between Uranus, Neptune, Saturn, and outer Jupiter and their accompanying moons and orbitals. To speed up the conquest of Sol, Perturabo unleashed waves of Pirate, Emperor's Children, and Night Lords vessels as well as ships of Traitor Space Marines which had since taken new colors or names. Though Titan had been cloaked in a ritual by Malcador for a future project, the rest of Saturn and Neptune were terrorized by these vicious bands of killers while Perturabo and Forrix led an assault on Jupiter itself, which was defended primarily by Imperial Fists, Imperial Army, and Blood Angels vessels under Captain Efried. In addition, the majority of the Second Sphere Fleet which had been held from the battle at Uranus were finally committed to the battle. Efried and Halbrecht's fleets slowly gave ground to the Iron Warriors in the vast expanse of Jupiter and her moons, eventually being forced to withdraw to Terra once the overall situation in the Sol System collapsed.[6e]
Fourth & Fifth Spheres
Amid the carnage erupting across the outer Sol System, Horus' most important maneuver came above the galactic disc. The combined Sons of Horus, Thousand Sons, Word Bearer, and Dark Mechanicum fleet plunged into the void between Terra and Mars. This force split then split in half, with the larger Dark Mechanicum contingent making for Mars while the Traitor Astartes force moved towards Luna. Along the way to Luna, Abaddon's armada was continually harried by the White Scars under Jubal Khan. However Abaddon and Zardu Layak were eventually able to board the White Scars flagship Lance of Heaven and slay Jubal in combat. At Mars, the large Dark Mechanicum fleet drawn from hundreds of treacherous Forge Worlds plowed into Camba Diaz's blockade fleet. Consisting of large numbers of Imperial Fists, Blood Angels, loyalist Mechanicum, and Imperial Army, this force was the largest of the four outer spheres and a vicious battle erupted over the Red Planet. From the Battle Barge Fortress of Eternity, Camba Diaz had to deal with attacks on both sides of his fleet as Kelbor-Hal's besieged Martian forces launched their own attack in conjunction with the arriving Dark Mechanicum armada. Understanding the time for a counterattack had arrived, Dorn and his command staff moved to the Phalanx, which finally left Terra's orbit and intended to contest the traitors at Luna and then Mars. Jaghatai Khan stated that the traitors had failed, as Horus' main fleet had yet to show itself and the firepower of the Phalanx would blunt this new attack, buying the loyalists enough time for Guilliman's arrival. [6e]
Meanwhile, Ahzek Ahriman's Thousand Sons force, accompanied by Word Bearers and their cultist-slaves under the Apostle of the Unspeaking, moved on The Comet between Venus and Terra, capturing it from light Servitor defenses and beginning a great sacrificial ritual prepared on the orders of Lorgar years prior. The ritual depended on an absolute timetable, having to be initiated at a precise celestial alignment in the Sol System that had not been seen since the Age of Strife. As Ahriman and the Word Bearers conducted their ritual, Abaddon's remaining Sons of Horus contingent emerged over Luna. The moon's defensive ring sported defenses greater than entire Expeditionary Fleets, and with the Phalanx inbound Abaddon's relatively small fleet seemed doomed to a quick death. However at the exact moment that Ahriman's ritual on The Comet was reaching its crescendo, Abaddon plunged his Battle Barge War Oath into the defensive ring around Luna as he and his warriors teleported aboard the moons surface. The kamikaze attack blew a 20 kilometer long gap into Luna's defensive ring as Ahriman departed The Comet, which became an epicenter for a massive black scar in reality which briefly blocked out the sun itself. From this tear in realspace came tens of thousands of traitor vessels including the full might of the World Eaters, Thousand Sons, and Emperor's Children. Besides conventional warships, this force also included hordes of winged Daemons. At the head of this impossibly vast armada's head was Angron standing atop the battlements of the Conqueror, Fulgrim aboard the Pride of the Emperor, and Horus himself commanding from the Vengeful Spirit. The new arrivals struck towards Luna, annihilating and scattering Battlefleet Solar and the Lunar defensive network.[6e] On Luna's surface, a Justaerin and Word Bearers assault under Abaddon and Layak eventually succeeded in securing the coveted Selenar Gene-Seed technology that had been used to create the original Astartes. The presiding Selenar Matriarch, Heliosa-78, ultimately chose to side with Horus than carry out her orders from Dorn to destroy her precious gene-tech before it could fall into traitor hands.[6f]
Dorn attempted to organize a counterattack aboard the Phalanx, but another one of Horus' trump cards took effect. The Remembrancer Mersadie Oliton, who had been brought aboard the battlestation by Garviel Loken due to an urgent need to speak to the Primarch, was revealed to have been unknowingly corrupted by Maloghurst years prior. From a warp-eye placed on her, the Daemon Samus emerged directly into the bowels of the Phalanx. Dorn's own command bridge was assailed by both Daemonic hordes and Samus' madness and in desperation the Primarch unleashed his Librarians which had been interred aboard the station since the Council of Nikaea. Not even the arrival of Sigismund's reinforcements from Pluto could turn the tide. Dorn fought Samus himself, but every time the Daemon died he was reborn by possessing one of the many nearby corpses. To end Samus' rampage, a distraught Oliton threw herself into the Phalanx reactor chamber, with her death closing the portal from which the Daemons were able to manifest. Though the Phalanx was now secure, victory in the Sol System was now impossible. Luna had fallen, Mars was rapidly being relieved, and Horus' armadas were closing in all around them. Dorn ordered that the Imperial Army Admiral Niora Su-Kassen take the Phalanx out into the outer Solar System in order to save it from certain destruction while he returned to Terra aboard Sigismund's Frigate Persephone. The surviving loyalist vessels in Luna's orbit either fled into the void or docked in Terra's atmosphere.[6f]
With the Solar System now in his hands, Horus was finally able to strike at the Throneworld itself. After a little over a month of fighting, on the Thirteenth day of Secundus the first orbital strikes from Horus' fleet fell upon Terra. The Siege of Terra had begun.[6f]
- 1: The Horus Heresy Book Six pg. 30
- 2: Praetorian of Dorn (Novel) Part 4, Chapters 1–6
- 2a: Part 1, Chapter 4
- 3: Secrets of the Solar War — Day 2
- 4: The Lightning Tower (Short Story)
- 5: Weregeld (Novella)
- 6: The Solar War (Novel)
- 7: Slaves to Darkness (Novel) - Chapter 19