Siege of Terra (Detailed) 1

Following the Drop Site Massacre, the traitorous Warmaster of the Imperium and of the Sons of Horus, Horus, had crippled three Loyalist Space Marine Legions. The Raven Guard and Salamanders were nearly destroyed, while the Iron Hands survived in larger numbers but were left leaderless. The fragmented warbands from these Shattered Legions continued hitting traitor forces during their advance upon Terra but were unable to contribute to the defense of the Throneworld itself. The Ultramarines, Space Wolves, and Dark Angels were either too far away or bogged down in their own campaigns to come for aid. Only the Imperial Fists, Blood Angels, and White Scars Space Marine Legions were in the Sol System in force.[1a]

Facing them were the armies of Chaos under Warmaster Horus which included nine Legions of Chaos Space Marines, traitorous forces of the Imperial Army, Daemonic hordes, and the Titan Legions of the Dark Mechanicum.[1a] Mars, the capital of the Adeptus Mechanicus, had recently fallen to the traitor forces. The situation had become disastrous for the Imperium and the forces of the Emperor. Horus, sensing that he could decisively end the conflict and overthrow the Emperor once and for all, began to move on Terra. Rogal Dorn, of the Imperial Fists, was given overall command of the defenses of humanity's homeworld while the Emperor himself was busy with his own secret project, the Golden Throne.[1a] In this endeavor, the Primarch was assisted by hundreds of specialists including: Fourth Master Tacticae Terrestria Julius Gundelfo, Tacticae Osaka, Montesere and Brinlaw, Data-Adjudicator Perez Grist, Imperial Army Colonel Lin-Hu Kway, Junior Administrar Patris Sator Omes, Cogitation Overseer Arnolf Van Halmere, and Rubricator Senioris Hyton Ki.[24r]

In addition to the loyalist Space Marine forces deployed in the Sol System, the loyalists were bolstered by the Custodian Guard, Sisters of Silence, millions of Imperial Army troops as well as various Mechanicum forces such as Titan Legions, Knights, Legio Cybernetica, and Skitarii. Much of Terra's population was forcibly conscripted in the stages before the battle, with millions of terrified Conscripts being handed a Lasgun with virtually no training. Most of these were deployed in the 3-layered trench network around the Walls of the Imperial Palace, with Dorn intending to save his Astartes and Mechanicum troops for the later stages of the battle.[9a]

Following the Battle of Beta-Garmon, the door to the Sol System was open and Horus finally mustered his forces on Ullanor after years of war. They included the Sons of Horus, World Eaters, Emperor's Children, Thousand Sons, Death Guard, and Iron Warriors under their respective Primarchs. These were bolstered by disparate forces of Night Lords under Captain Gendor Skraivok and 5,000 Word Bearers under Zardu Layak. The Alpha Legion left the Solar warzone after delivering a detailed map of the Sol System's defenses to Horus.[4] During the final phase of the Solar War, Horus' forces captured the Sol System from the loyalists. All that now lay his path to victory was Terra itself.[7] Horus intended to capture Terra before the arrival of Roboute Guilliman from the galactic east, though he deployed Perturabo and the Iron Warriors to fortify the captured Sol System against any who may intrude upon the siege.[9a]

The Storm Breaks

The siege of the Imperial Palace.

On the thirteenth day of Secundus, the bombardment of Terra began. From orbit, Horus' ships laid down an unrelenting barrage of missiles and energy beams. The first shell targeted the Sanctum Imperialis, the Emperor's personal quarters, for symbolic reasons, though it did no damage and was quickly intercepted by many point defense systems. A vicious exchange of fire took place as the massive array of anti-ship gun batteries on Terra opened up on the traitor ships. Losses were incurred by both sides, but the traitor fleet in particular took heavy losses in space but endured through sheer weight of numbers.[9a] Horus' ultimate objective was the Imperial Palace, seat of the Emperor himself. The orbital bombardment was some of the most intense ever witnessed and shook even the courageous and battle-hardened loyalists Space Marines.[1b] However damage to the actual Palace itself was minimal due to a sophisticated multi-layered and self-repairing Void Shield system known as The Aegis as well as the fact that Terra's last orbital plate was placed over the Palace to serve as a shield and gun platform. However, due to a reactor flaw in one of the Aegis' reactors, a small weakness appeared in the Palace network centered around a Bastion outside the Helios Gate.[9a] Inside the depths of the Palace itself, the Emperor, attempting to keep the Golden Throne under control, could only brood over the desperate events occurring far above.[1b]

The loyalist generals plot the defence of the Palace

The bombardment continued for days as Perturabo probed for weaknesses in the Aegis, discovering the flaw around Bastion-16. The Aegis around this area was weakened enough to allow for slow-moving aircraft to penetrate. Despite the ragings of Angron and the boredom of Fulgrim, Horus would not launch an all-out attack yet. The Emperor's might not only prevented Daemons from manifesting on Terra, but also threatened to destroy the Daemon Primarch's should they set foot upon its soil. Magnus and Zardu Layak surmised a ritual to eliminate the Emperor's barrier by spilling enough blood across Terra. Horus began to increasingly spend his time comatose, his spirit inside the Warp searching for lore as well as weakening the Emperor's spirit,[9b] eventually designating First Captain Ezekyle Abaddon as his proxy.[9d] After 12 days the bombardments continued, but were matched with the first ground assaults. Thousands of traitor vessels crashed into Terra's surface. Many were destroyed by the Palace defenses, but many more landed and unleashed endless hordes of Traitor Imperial Army, Beastmen, Cultists, and Mutants. These were largely distractionary measures to support the traitors' true objectives as they ravaged the planet, as well as support the traitor aerial attacks on the Palace's anti-ship guns and void shield generators. The loyalists responded with their own aerial defenses, and massive dogfights erupted over the Palace as the conscripts outermost trenches around the walls held against the attacks by the Lost and the Damned. While the Palace held, elsewhere across Terra major population centers fell such as Lundun, Noy Zaylant Hive, Neork, and Braslya.[9l]

The Dark Mechanicum siege camps around the Imperial Palace

The pattern of orbital attack, landings by traitor rabble, and aerial assault repeated itself for weeks before the Death Guard fleet under the now-corrupted Mortarion arrived at Terra. True to his earlier word to let Mortarion's legion be the first to set foot upon Terra, Horus prepared to use the Death Guard in the first Astartes-led assaults on the Palace.[9d] This caused Angron to rage, and to prevent him from destroying his own flagship The Conqueror he was teleported by World Eaters 8th Company Kharn into the ever-shifting labyrinth originally built for Vulkan aboard the Night Lords flagship Nightfall.[9f] On the seventh of Quartus the first Death Guard Drop Pods landed on Terra's soil as the Nine Disciples of Kelbor-Hal each beached one of their Ark Mechanicus-class Battleships around the Palace. The Void Shields and bulk of the Ark Mechanicus vessels allowed for the traitors to establish their first real footholds around the Palace, and as the Death Guard unleashed gas and plagues upon the trenches around the walls the Dark Mechanicum set about their work of constructing siege engines.[9e] The Death Guard assault on the outermost trenches around the Palace was about to break the Imperial Army defenders until Jaghatai Khan, defying Dorn's orders to remain in the palace, led a Jetbike charge by the White Scars. The Scars pushed past the traitor frontline into their siege camps before the Khan was finally forced from his Jetbike. Jaghatai slew dozens of Death Guard until he was wounded by a Warp-tainted poisoned blade. Ultimately Sanguinius had to sortie out of the Palace with his Sanguinary Guard to rescue Jaghatai, who recovered from his Warp sickness as soon as he began to move closer to the Sanctum Imperialis and the psychic might of the Emperor. The Khan's move was not reckless however, he also gathered valuable intelligence on the siege engines the traitors were constructing.[9g] Meanwhile aboard the Vengeful Spirit, Horus finally allowed Perturabo to begin his preparations to clear landing zones around the Palace for their Titans.[9h]

The Imperial Palace under siege[2]

On the Fifteenth of Quartus, the traitors initiated their dual plan to break The Aegis and allow for the manifestation of Daemons upon Terra. A giant projected face of Zardu Layak appeared on an island of bones which descended from the sky, urging the commoners of Terra to rise up against the Emperor and ensuring them that if they turned to Horus now they would be spared. The Palace guns could not silence the corporeal island, and after his speech concluded it began to rain blood. The blood signaled that the traitors had finally undertaken their ritual to weaken the Emperor's psychic barrier, and the Mechanicum released their Daemon Engines. Eight "Warp-Bane" guns constructed near the sites of the beached Ark Mechanicus vessels opened up on the Aegis Shield around the Palace, sapping it of its energies as the Death Guard deployed massive Towers of Nurgle at the walls. As the Aegis gave way the traitor bombardment finally was able to hit the Palace defenses directly, causing massive devastation and allowing for a Night Lords Raptor assault on the Eternity Wall. -