Siege of Terra

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Siege of Terra
Date	0014.M31
Scale	Planetary
Theatre	Horus Heresy
Status	Pyrrhic Loyalist Victory
Belligerents
Traitor Legions	Imperium of Man
Commanders and Leaders
Horus, Angron, Mortarion, Fulgrim, Perturabo, Magnus the Red, Zardu Layak, Kelbor Hal	The Emperor, Sanguinius, Rogal Dorn, Jaghatai Khan, Vulkan, Malcador the Sigillite, Constantin Valdor
Strength
Sons of Horus, Death Guard, World Eaters, Emperor's Children, Thousand Sons, Iron Warriors, Word Bearers, Night Lords, Traitor Army forces, Dark Mechanicum, dozens of Traitor Knight houses, Traitor Titan legions, daemons	Imperial Fists, Blood Angels, White Scars, Adeptus Custodes, Sisters of Silence, Knights-Errant, Imperial Army, Adeptus Arbites, dozens of Knight Houses, loyalist Titan Legions (Gryphonicus, Ignatum, Solaria, Atarus, Amaranth, Ordo Sinister)
Losses
Massive Heretic Astartes casualties, massive Traitor Army losses, massive Traitor Titan losses, massive Dark Mechanicum losses. Horus slain. Angron, Mortarion and Magnus banished.	Massive military and civilian losses. Malcador the Sigillite slain. Sanguinius slain. Emperor mortally wounded and interred into Golden Throne.
Outcome
Traitors driven from Terra and into the Eye of Terror. Death of Horus and crippling of the Emperor. Great Scouring Begins.

"He waits no longer. It begins now."

– Sanguinius on the 13th of Secundus, 014.M31

The Siege of Terra was the end of the Horus Heresy in Warhammer 40,000. If the Horus Heresy can be considered the most important series of events in the 40k universe (*cough* War in Heaven), then the Siege of Terra itself could be considered the single most important event. It is also possibly the most fucking awesome event: brothers fighting brothers, Primarchs (read Sanguinius) soloing Titans and Greater Daemons, continent-spanning trench battles, the mighty guns of Titans blowing mountain-sized fortifications to shreds, Imperial Army soldiers leading charges against the traitorous forces even though they know it's suicide and Ollanius Pius making a desperate stand against impossible odds.

It was Horus's big attempt to off his daddy and to be the true Emperor of the galaxy (for Chaos of course!). He brought a load of his traitor legions, millions of corrupt Imperial Army personnel and mutants, the part of the Mechanicus that had gone over to his side, and a whole load of daemons to boot. On his side, the Emperor had three legions, his Custodians, and the loyal Imperial Army regiments of Terra and you know what? The Emperor went and won anyway (granted it was because the Emperor offed Horus before his legions could crack the Imperial palace but still, victory for the home team!).

The Solar War

Dorn began fortifying Terra immediately after getting word of the Heresy, knowing that it would always be Horus's eventual goal. Despite being removed from the larger battles of the Heresy, the Solar System was touched by the conflict, with Mars erupting into open rebellion and numerous sleeper agents and cults trying to destabilise the Throneworld. Despite this Dorn managed to do the best he could, turning Terra into the most heavily fortified system in the Imperium. He even managed to blunt part of the traitor advance at the Beta-Garmon cluster before getting ready for the final rumble they had known was coming.

Terra was unique in that it had two artificial Mandeville points inside the Solar system itself, created during the Dark Age of Technology. Dorn fortified the likely approaches from the outer edge of the system and built up huge defenses around the two internal jump points. The traitors, however, were busy too: infiltrators and covert operatives sabotaged loyalist assets across the system. The Iron Warriors were the first Astartes into the breach, breaking the Warp on the First of Primus, 014.M31, using huge up-armoured Space Hulks as fireships to wear down the defenses before sending their main fleet through to engage the combined Fists and Scars fleets. The inner system conflict went on for a bit, with the loyalists managing to hold out enough to slow down the advance at least for a little while.

However, under Magnus's direction, the traitors turned the Shrine of Unity comet into a vast Warp gate that allowed Horus, Angron, and Fulgrim's fleets to jump right past most of the rings of defense Dorn had come up with. On the Phalanx, Dorn was preoccupied with a daemon incursion and could do little to stop the huge fleets that were now mobbing for Terra. The Martian traitors, free from the blockade that had hemmed them in for years, joined up with Horus. The Solar War had barely lasted a month, far far less than the loyalists had hoped for. The rest of the loyalist fleets, knowing they could never hope to fight even a fraction of the vast traitor armada, regrouped on the edge of the system, along with the Phalanx, waiting for the moment they could make an effective strike against Horus. There were early plans for the Emperor to be evacuated to the Phalanx and escape Terra, but these were made by people unaware of what Big-E was doing in the basement of the palace.

The Siege Begins

Map of the Siege.

"Father! I have come for you!"

– Angron upon making planetfall, 15th of Quartus, 014.M31

Uncontested, most of the traitor armada held in orbit above the Palace, and on the Thirteenth of Secundus, began bombarding the Aegis, the vast shield network protecting the entire palace complex. Unlike regular void shields, the Aegis consisted of multiple overlapping layers of shields that individually regenerated as fast as they could be depleted by bombardment. On the ground, the Palace was protected by colossal networks of walls and bastions, static defenses, and vast numbers of Imperial Army units bolstered by hordes of press-ganged conscripts. Unknown to almost everyone, the Inner Palace was also protected by a psychic ward generated by the Emperor that would royally fuck up any daemon that set foot near it, daemon Primarchs included.

The rest of Terra wasn't so lucky. Barring a few isolated holdouts, the rest of the planet was virtually defenseless. It should be noted that if the goal was to destroy Terra wholesale, it could have been easily accomplished by Exterminatus-level weaponry. Perturabo, as the only non-Chaos-ified Primarch, insisted on doing exactly that and grew increasingly angry at what he saw as an irrational and wasteful goal. But Horus was insistent that the Emperor had to be slain in person, and so the Palace had to be reduced the old-fashioned way. In all fairness, one must also ask if Exterminatus was even possible when a being like the Emperor was on Terra, to say nothing of the void shields and defenses on Terra itself (with the answer depending on how much Ext-grade weaponry and warheads the Chaos forces could bring along). The daemon primarchs were kept in orbit, safe from the Emperor's wards, although this meant that Angron had to be imprisoned in the maze Perturabo had built to contain Vulkan to stop him from Leeroy Jenkinsing the whole thing as he had done at Istvaan III.

Hordes of mutants, beastmen, cultists, and traitor Army units were thrown at the conventional defenses. Entire wings of aircraft dueled above the Palace. Precision bombardments gradually weakened minute sections of the Aegis long enough for bombers to get through and destroy the projectors. The Dark Mechanicum landed siege camps at 8 points around the Palace, partly to surround it but also to act as the focus for a ritual that would enable the Warp to take a foothold on the surface of the Throneworld. The Dark Mechanicum also began building massive siege towers to get Traitor Legionaries on the Wall. The Astartes were held in reserve on both sides whilst their more conventional forces softened each other up. The Death Guard were the first traitor Astartes to land on Terra, with the Khan and the White Scars riding forth on jetbikes and aircraft to meet them and wreck the Dark Mechanicum's siege camps. The Night Lords were the first Astartes to breach the walls of the Palace, albeit in small numbers; this attack also cost them their de facto commander, Gendor Skraivok. Sanguinius himself descended to help the mortal forces, acting as force multiplier, decoy, and morale booster.

Unfortunately, by that point, enough bloodshed had occurred that the Emperor's wards were now reduced to just a few meters from the walls of the Palace, meaning daemons could now manifest on Terra. Horus responded by sending the World Eaters as the second wave, and this time Angron was leading the charge. Recognizing the outworks were about to be overrun, Sanguinius used an impending sally by the Legio Solaria to evacuate the surviving conscripts through the Helios Gate, while Legio Solaria destroyed the remaining siege tower. The loyalists had managed to repulse the first serious attempts on the Eternity Wall, but were now completely cut off from the rest of Terra, surrounded on all sides.

The Lion's Gate Space Port Falls

Map of the Lion's Gate Space Port.

While the Death Guard, Emperor's Children, and World Eaters each hammered away at a different section of the Palace walls, the traitors' first major effort at cracking the Palace itself was aimed at the Lion's Gate spaceport, the largest and tallest spaceport on Terra. It reached so high into the atmosphere that void craft could dock at its upper levels, meaning that the traitor forces could more easily shuttle in reinforcements and materiel if they captured it. Horus tasked the Iron Warriors with taking the space port. In turn, Perturabo assigned Warsmith Kroeger to lead the assault under the logic that Dorn would be expecting Pert to command such an important offensive personally and wouldn't be expecting whatever plans Kroeger came up with. Dorn assigned Seneschal Fafnir Rann to lead the defense of the spaceport rather than First Captain Sigismund since he was still angry with Sigismund for listening to Euphrati Keeler instead of obeying his orders. Kroeger went straight for the throat, launching a massive combined-arms assault directly on the port with backup from the World Eaters and Emperor's Children, though the latter quickly got bored and left after taking a bunch of prisoners for unspecified purposes. Though the Imperial Fists held off the initial attack, Warsmith Forrix and a thousand Iron Warriors managed to infiltrate the port by using renegade Imperial Army units as literal meatshields. To aid the attack, the Dark Mechanicum inserted a technophagic virus into the spaceport's systems, and Zardu Layak, Abaddon, and Typhus performed a Nurglite ritual to infiltrate the Daemon Prince Cor'bax Utterblight behind the Emperor's psychic wards.

The Fists drove back several consecutive assaults from the Iron Warriors and World Eaters, but the technophage was screwing their sensors and comms all to hell and gone, seriously complicating efforts to coordinate the defense, and Forrix and his infiltrators were tying up troops that were desperately needed elsewhere. Rann finally called Dorn for backup and Dorn scraped up an additional three thousand Fists under Sigismund, which were literally all the troops he could spare at that point. Despite Rann's best efforts, the balance inevitably tipped in the traitors' favor. Dorn arrived on the scene just in time to order a general withdrawal from the spaceport to the inner defenses, though not before he killed Zardu Layak after a brief duel. With the spaceport firmly in the traitor hands, Perturabo started unloading Titans and consolidating his position.

Meanwhile, Euphrati Keeler and the Custodian Amon Tauromachian had been tapped by Malcador to investigate strange apparitions occurring behind the Palace walls. They eventually deduced that this was a daemon exploiting the faith of Imperial cultists to manifest itself inside the Emperor's psychic defenses. One cult, in particular, called the Lightbearers, had been deceived into worshipping Nurgle instead of the Emperor. After Cor'bax used the Lightbearers to physically manifest himself inside the Palace, Amon, Euphrati, and Malcador teamed up to slay the daemon. When Amon suggested that they should purge the rest of the Emperor's worshippers to prevent another such incident, Malcador answered that he would continue to let them exist until the Emperor himself said otherwise, in the hopes that he could weaponize their faith against the Chaos gods.

Battle at the Saturnine Wall

Just 0.000001% of 0.000001% of the Siege of Terra.

This page is in need of cleanup. Srsly. It's a fucking mess.

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With the Lion's Gate space port lost, Dorn was now under tremendous pressure as he continued to coordinate the defense in the face of the unrelenting traitor assaults. Nearly all the Traitor Legions were committed to the battle at this point, with the Death Guard, Iron Warriors, Thousand Sons, Emperor's Children, and the Sons of Horus engaged in heavy fighting at the Anterior Barbican, a series of six fortresses protecting the Lion's Gate, while the World Eaters and the more Chaos corrupted Army regiments went on a rampage throughout the Palace's outer districts, tying down loyalist reinforcements in the Sprawl Magnifican. Additionally, the Lion's Gate spaceport allowed the Dark Mechanicum to begin landing Traitor Titans Legions inside the Palace walls, as well as Armour for the Traitor Legions and Army. Dorn could only muster his own legion, plus the Blood Angels and White Scars and their primarchs, along with what Army and Mechanicus units were stationed in the Inner Palace.

While taking a brief break in an abandoned garden, Dorn encountered Kyril Sindermann, who made an offhand comment about the Saturnine Wall trembling under the weight of the bombardment. From this, Dorn deduced that something was wrong with the defenses in that section and investigated. What he found was a potential catastrophe. The ceaseless bombardments from the traitor forces had caused the entire Imperial Palace and the tectonic plates on which it rested to shift by eight centimeters, opening a small but detectable fault line which had been previously sealed beneath the Saturnine Wall.

Certain that Perturabo would notice this fault and attempt to exploit it, Dorn began concocting a counterattack. Before laying out his plans, he called a council of war with Constantin Valdor and Malcador to explain to them his next move: he would have to start allowing parts of the Palace defenses to fall, as he simply no longer had the numbers or the materiel to hold everything. He identified four key parts of the defense that could not be allowed to fall to the enemy - the Colossi Gate, the Gorgon Bar, the Saturnine Wall, and the Eternity Wall spaceport - then chose the one he could most afford to lose based on his calculations, which was the spaceport. Though he would put on a show of defending it, Dorn knew that the port ultimately had to be sacrificed, even though it meant letting the traitor forces control both of the Palace's main spaceports. He assigned Sanguinius to hold the Gorgon Bar and Jaghatai Khan to hold the Colossi; he would personally oversee the defense of the Saturnine Wall and lay a trap in the hopes of bagging a significant enemy target, perhaps even Horus himself.

Perturabo had indeed spotted the weakness at the Saturnine Wall, though he had initially planned to use it only as a last-ditch ace in the hole, content to break the Anterior Barbican at either Colossi Gate or Gorgon Bar with what they had already landed, or wait for the World Eaters to inevitably overrun the Eternity Wall port and allow them to land reinforcements to fully overwhelm the two fortresses. Abaddon convinced him to instead make it a focal point of the attack through a combination of flattery and unsubtle goading, suggesting that Perturabo's victory over Dorn would be tainted if it was won with the help of the Neverborn. Though the Lord of Iron nearly caved his face in for it, Abaddon won the argument and immediately set out to assemble a spear-tip strike. Secretly, he was also hoping to win a "clean" victory without resorting to the use of daemons and sorcery, as he believed that using the Warp to win a war was beneath his dignity as an Astartes.

The battles for the Colossi and the Gorgon Bar escalated in scale and intensity. The defenders at the Colossi Gate were plagued by legions of flies that seemed to manifest from nowhere, forcing them to wear bulky protective equipment that lessened their effectiveness. Sanguinius was suffering under the weight of his psychic visions, which were coming with increasing frequency and intensity; nevertheless, he continued to fight on the front lines, knowing that his mere appearance was heartening the defenders and raising their morale. At one point he singlehandedly killed a Warlord Titan, then stared down its three accompanying Warhounds until they turned tail and fled. At the Colossi, Jaghatai and the White Scars led a few massed jetbike charges into the ranks of the Death Guard, destroying their siege engines, killing their Neverborn reinforcements, inflicting casualties, and generally delaying the XIV Legion's inexorable advance. The Adeptus Custodes also engaged the Death Guard, with Constantin Valdor himself taking the field. Their Emperor-forged nature proved especially potent against the Warp-corrupted Marines of the XIV and their daemonic allies. Ahriman and the Thousand Sons attempted to literally melt the Colossi bastion with sorcery, only to be driven back by three White Scars Stormseers who channeled the captured weather underneath the Palace's void shielding into an immense lightning storm.

At the Saturnine Wall, Dorn had devised a simple but cunning trap. Its cellars and tunnels had been fortified and transformed into a series of Zones Mortalis, and he had assembled a five-hundred-man strong force of veteran Astartes, broken into seven kill teams led by Sigismund, Nathaniel Garro, Endryd Haar of the World Eaters, Garviel Loken, Bel Sepatus of the Blood Angels, Helig Gallor of the Death Guard, and Maximus Thane of the Imperial Fists. He had also enlisted the technoarchaeologist Arkhan Land to help him mend the fault line; Land devised a quick-setting form of rockcrete which could be pumped into the fault to seal it permanently. Dorn didn't know who would be leading the assault, but he was hoping for Horus himself. Once cut off and isolated inside the Palace walls, even the Warmaster would be relatively easy prey. On the other side, Abaddon was able to convince Fulgrim to lend him the entire Emperor's Children Legion for the assault on the Saturnine and wrangled three companies of the Sons of Horus to form the spear-tip. The III Legion would attack from the front as a diversion, using three Donjon-class siege engines borrowed from the Dark Mechanicum, while Abaddon and his Astartes burrowed up from beneath with Termite assault drills.

They had walked straight into Dorn's trap. When the first Sons of Horus emerged from their assault drills, they were ambushed by Dorn's kill teams, who achieved total surprise. The assault force was DESTROYED IN DETAIL, which is to say that of the hundreds of elite combatants committed to the attack (which included the famed Justaerin Terminators and Catulan Reavers of the 1st Company, all four members of the Mournival leading their respective companies, as well as two more veteran companies led by Tybalt Marr and Lev Goshen respectively) the number of survivors could literally be counted on one hand with fingers to spare. Garro decapitated Falkus Kibre of the Justaerin, while Loken killed Tybalt Marr, Horus Aximand, and Tormageddon. Just as the loyalists were starting to relax, Abaddon and a hundred Justaerin Terminators teleported into their midst, triggering a giant brawl. Abaddon went on a killing spree, but eventually absorbed a series of crippling blows from Bel Sepatus and Endryd Haar. Though he managed to kill them both, he wound up pinned under Haar's corpse, with Garro poised to deliver the killing stroke. Luckily for Abaddon, he was teleported to safety at the last moment, as the Chaos Gods had already chosen him to be the new Warmaster after the death of Horus. Arkhan Land began pumping hundreds of thousands of liters of his rockcrete formula into the fault. Though he was briefly interrupted by Horus Aximand, the plan went off without a hitch, and the fault was permanently sealed. Some of the remaining Sons of Horus had yet to emerge from their assault drills and became trapped in the rockcrete as it set, ensuring that they would be entombed beneath the Palace forever. Barring any future statements to the contrary, it appears that literally the only survivor of this deflated, wilted bit of tactical flailing, once laughably referred to as a spear-thrust, was the very armless failure that advocated so strongly for it. Oops.

Aboveground, Fulgrim had unleashed a full-scale assault against the Saturnine Wall, leading off with the Donjon siege engines, which had been modified with immense sonic weapons similar to those of the Kakophoni. The engines seriously disrupted the defense at first, but the Imperial Fists and Army garrison were able to rally and funnel the III Legion into a chokepoint. Fulgrim got into a duel with Sigismund atop the Wall. Though the Templar was able to land a few hits, Fulgrim's daemonically enhanced strength and speed gave him the upper hand. Before he could kill Sigismund, Dorn intervened and proceeded to pummel Fulgrim badly enough that the Phoenician threw a tantrum and took his legion and went home, abandoning the Siege entirely and costing Team Horus one of its most significant force multipliers. Fulgrim left fifty-six of his best warriors behind in an attempt to kill Dorn, but he and Sigismund were able to defeat them all, including Eidolon and Von Kalda. The assault wound up costing the Emperor's Children no less than eighteen thousand Astartes, along with all three of the irreplaceable siege engines.

This great victory had been purchased with an equally great loss: the fall of the Eternity Wall spaceport. Despite the garrison's best efforts to hold the port, they were faced with the Chaos-fueled rage of Angron and the World Eaters. Angron issued a demand for the port's defenders to surrender and was met with a concentrated artillery barrage that literally atomized him, though being a daemon prince, he didn't stay down for long. He and his legion immediately assaulted and seized the spaceport, killing everyone present. Many heroes of the Imperium died unheralded deaths at the Eternity Wall, including Knight-Commander Jenetia Krole of the Silent Sisterhood, Prefect Warden Tsutomu of the Adeptus Custodes, High Primary Solar General Saul Niborran, and Captain Camba Diaz of the Imperial Fists (who died holding the line in one of the greatest displays of manliness in the universe). A lone Guardsman named Olly Piers died there also, defending a banner of the Emperor Ascendant against Angron's relentless charge, thus establishing the foundation for one of the Imperium's most enduring myths after a considerable amount of embellishment at his dying request. Ironically, Piers was a distant descendant of Ollanius Persson.

In the aftermath of these battles, Dorn and Sanguinius took stock of where they stood. The Gorgon Bar had held and would continue to hold for two precious weeks more by Sanguinius' estimate. The repulse at the Saturnine Wall had cost the Traitor Legions dearly. Three hundred of the XVI Legion's elite troops and eighteen thousand Emperor's Children were dead, with Fulgrim and the rest of the III Legion having quit the field. Jaghatai Khan, having held the Colossi, was now preparing to retake the Lion's Gate. Better yet, Sanguinius' prescience had granted him a vision from within the depths of Angron's tortured mind: Nuceria had been destroyed - not merely razed as Angron and Lorgar had done during the Shadow Crusade, but obliterated by orbital bombardment. Dorn and Sanguinius both knew this could mean only one thing: Roboute Guilliman and Lion el'Jonson were on the way along with their legions.

Admiral Niora Su-Kassen, now in command of what remained of the loyalist naval assets in the Solar system, received indications of another fleet approaching from the outer edges of the system. She ordered the new arrivals to announce themselves, and was answered with a hail from Corswain of the Dark Angels: "We come to stand with Terra."

Assault on the Mercury Wall and Recapture of the Astronomican

With the repulse at Saturnine and the fall of the Eternity Wall spaceport, the Siege was entering a new phase. With both of the Imperial Palace's primary spaceports in their hands, the traitor forces began bringing in all their reserves and materiel stores, preparing to overwhelm the loyalists through sheer numbers. Perturabo was still directing the battle more or less singlehandedly at this time until he received a summons from Horus to attend him on the Vengeful Spirit. When the Lord of Iron arrived in Horus' throne room, the Warmaster instructed him to abandon his current battle plan. Instead, he wanted to throw everything they had, including the Titan Legio Mortis, straight at the Mercury Wall, which represented the true beginning of the Imperial Palace. Perturabo demanded to know why Horus wanted to employ such a wasteful and apparently futile strategy, and Horus stated that it would work because he willed it so. Shortly thereafter, Horus sent his equerry to Perturabo with orders to disperse the Iron Warriors among the traitor forces. He followed up this humiliating order by informing Perturabo that Mortarion and the Death Guard would be taking over the IV Legion's positions. Infuriated, Perturabo denounced Horus' alliance with the Ruinous Powers and declared that this was no longer a war of Legions, but a war of foul and unnatural powers in which no true victory could be won. He then bitterly declared that Horus was exactly like the Emperor: both of them had manipulated Perturabo from the very beginning and forced him into a role he despised, that of the ruthless, calculating siege master. With that, he ordered the IV Legion to withdraw from the battlespace. A few diehards chose to remain behind, but nearly the entire legion obeyed their primarch's order. Some of the traitor forces attempted to stop the Iron Warriors as they headed for the exits, but were unsuccessful.

Unbothered, Horus ordered the attack on the Mercury Wall to proceed, spearheaded by Legio Mortis. To counter the Death's Head, the loyalists deployed the Legio Ignatum and a few Titans from Legio Solaria, along with Knight banners from Houses Vyronii, Tyranus, Cadmus, and Konor. A representative of the Mechanicus attempted to convince Ignatum's Titan drivers to flee the battle, as his calculations had shown that defeat was inevitable, but the principes rejected his proposal and walked to war anyway. Also present were a number of other Titans from legions that had been decimated at Beta-Garmon, but many of them refused to join the battle, citing the Titandeath as their reason for remaining out of the fight. This lasted until the engagement between Mortis and Ignatum began, in a vast open space known as the Mercury-Exultant killzone. The traitors were revealed to be using Titans that had been destroyed at Beta-Garmon and elsewhere as cannon fodder; the wrecked Titans had been reanimated via sorcery and now teemed with blight and corruption. Ignatum smashed through these revenants, only to be confronted with the main strength of Legio Mortis. A desperate battle ensued, with dozens of god-engines being destroyed on both sides. Proscribed weapons such as warp and vortex missiles were employed freely, for this was now a battle of annihilation. Recognizing the import of the engagement, the Emperor communicated with a representative of the Ordo Sinister, the commanders of the dreaded Psi-Titans, and ordered him to join the battle. One of their prefects made himself known to Dorn, who agreed to deploy the four available Psi-Titans into the battle. He then took command personally at the Mercury Wall, bringing reinforcements with him. Ambassador Vethorel of the Adeptus Mechanicus approached the Titan crews who had refused to join the battle and showed them images of the reanimated Titans being used by the traitors. Galvanized by the desecration of their fellow god-engines, the Titan crews agreed to rejoin the fight. Vethorel proclaimed them to be a new Legio, the Legio Invigilata. Led by the former Grand Master of Legio Solaria, Invigilata joined Ignatum and the Psi-Titans on the front line. In spite of the loyalists' bravery, the main strength of Ignatum was destroyed by the superior numbers and firepower of Legio Mortis, combined with an orbital bombardment from the traitor fleet. The survivors attempted to rally and continue the fight, but Mortis had reached the Mercury Wall and began to tear it down.

During this battle, Corswain of the Dark Angels was conferring with Admiral Su-Kassen and other leaders of the Imperial fleet. Corswain had been expecting to find the rest of the I Legion already present at Terra and was dismayed to learn that he and the forces under his command were the only Dark Angels in the system. He had brought only ten thousand Astartes and two dozen ships with him, barely enough to make any kind of impact against the enemy forces in orbit. Unwilling to sit by and do nothing, Corswain announced that he intended to recapture the Astronomican, which had fallen into traitor hands and gone dark. Without it, the I and XIII Legions would be unable to reach the system and relieve Terra. Some of the Dark Angels in his fleet, having been subverted by Luther's separatist faction, wanted to assassinate Corswain to avoid being wasted on what they considered a pointless suicide mission. They were talked down by Librarian Vassago, who was a member of their faction but admired Corswain's bravery and nobility. Admiral Su-Kassen agreed to lend them the Imperator Somnium, an immense battle carrier that had served as one of the Emperor's personal flagships, for their attack. The Dark Angels proceeded to use the Somnium as a sort of fireship. Concealing their own vessels under its tremendous bulk, they rode in with the huge flagship as it drew the fire of the entire traitor fleet, then split away and charged through to the Astronomican before the traitors realized what was happening. The Somnium died hard, taking many enemy ships with it and inflicting critical damage on the Conqueror and Terminus Est. The Dark Angels successfully landed at the Astronomican and breached its defenses. They found that the mountain had been overrun by elements of the Emperor's Children and Vassukella, a Daemon Prince of Slaanesh. Despite sustaining heavy casualties, they were able to kill Vassukella and the corrupted Children, reclaiming the Astronomican for the Imperium. Corswain was nearly killed by the psychic backlash of the daemon's death, only to be saved by Vassago. The news that the Astronomican was once again in friendly hands provided a much-needed morale boost to the Imperial forces, though this was offset by the grim news from the Mercury Wall.

Subsidiary combat continued all along the Palace's defensive perimeter, though it was comparatively small in scale when measured against the annihilating fight taking place at the Mercury Wall. The loyalists were beginning to reach the limits of their mental, physical, and spiritual endurance, though some of them took confidence in a new credo: "He protects us as we protect Him." Even so, the loyalists' morale was being further eroded by the malign influence of the Warp. Those who were sensitive to its currents and eddies noted that its strength was waxing as the Siege ground on, working its way through the cracks in the Emperor's wards and battering down the mental defenses of the loyalist troops. Suicides, murders, and desertions spiked as exhausted and despairing soldiers and civilians sought to escape into a paradisaical dreamland. Unfortunately for them, this dreamland was a trap laid by the Emperor's Children to prey on the desperate and fearful. Thousands of unfortunate souls were lured to the Hatay-Antakya Hive, where the III Legion entrapped them in their dreams and "milked" them for their emotions. These activities were disrupted by the arrival of Ollanius Persson and his band of refugees from Calth, who were seeking to rendezvous with John Grammaticus and his prototype Space Marine bodyguard Leetu. They in turn were aided in their escape by a mysterious woman calling herself "Actaea" and a legionary in scaled armor who identified himself as Alpharius. Together, this unlikely group of allies embarked on an unspecified mission involving the Emperor.

Second Battle for the Lion's Gate and the Rise of the Emperor's Champion

With the Mercury Wall breached, the Siege was reaching its endgame. The loyalist forces were being slowly shoved back into the innermost circles of the Palace defenses. Comms were unreliable at best, supplies were running low, and sheer exhaustion and hopelessness were grinding the defenders down. Angron and the World Eaters were loose inside the Palatine, with the Sons of Horus following behind. The Death Guard occupied the Lion's Gate spaceport, taking over after the IV Legion's abrupt departure from the battlespace. As their tainted presence began to warp the port into a twisted mirror of Barbarus, Mortarion established himself in one of its command centers, using his new daemonic powers to amplify the currents of the warp and blanket the Palace in a psychic miasma of despair. The effect was so potent that even Rogal Dorn's legendary resolve was cracking under the weight of Mortarion's malignant influence. He had bent all his prodigious intellect and unmatched engineering skill toward transforming Terra into the mightiest fortress the galaxy had ever seen, and it had not been enough. Without Guilliman and the Lion and their legions, they were doomed to inevitable defeat.

Jaghatai Khan, frustrated by the passivity of static defense, decided to launch a counterattack on the Lion's Gate. His reasoning was sound: should the Dark Angels and Ultramarines arrive to relieve Terra, they would need a place to dock their voidcraft. Moreover, the powerful anti-orbital batteries of the Gate could be turned against the traitor fleet. With his decision made, he quietly assembled the V Legion while his friend and Army liaison Ilya Ravallion scrounged up every functioning tank she could find to support the assault. The Khagan also recruited the Skye orbital plate to serve as a shield against the guns of the traitor fleet, knowing that they would bombard his forces as soon as they were visible. The gathered tanks were formed into a new unit, the First Terran Armoured, and sortied alongside the V Legion, deployed into three massive attack groups. They shouldered their way through the outer defenses easily enough, using the tanks to smash the Death Guard's armored spearheads and deploying Stormseers to wipe out any daemons that manifested themselves. The V Legion's usual tactics of speed and shock power served them well in this stage of the assault, but things became much harder when they reached the spaceport. The battle turned into an attritional slugging match, with two of the three attack groups bogging down almost immediately. Only the group led by the Khagan himself made any headway, tearing through the massed ranks of the XIV Legion and breaching the Gate itself. The fighting grew steadily more desperate; the mortal tank crews were being pushed to their limits and beyond by the nature of the fighting, which required them to remain sealed inside their tanks at all times lest they fall prey to chemical weapons or warp-borne plagues, and the White Scars were stymied by the unnatural resilience of their foes.

As the battle continued to rage throughout the port's lower levels, the Khan infiltrated Mortarion's command center and challenged his brother to a duel. They fought like madmen, with nothing held back, but Mortarion's unnatural strength gave him the edge. He wrecked Jaghatai's armor, broke his arms and ankles, and smashed his face into a pulp. The Khagan stood up, laughing off wounds that should have killed him, and attacked again. He taunted Mortarion relentlessly until the Death Lord became enraged enough to make a mistake. The Khan skewered him, only for Mortarion to recover and bury his scythe in the Warhawk's chest. Which was exactly what the Khan had wanted him to do. Jaghatai had allowed Mortarion to deliver a killing stroke so that he could deliver one in return. He beheaded his corrupted brother, banishing Mortarion to the Warp and unleashing a psychic shockwave that staggered and disoriented the Death Guard. In the aftermath, Jaghatai succumbed to his wounds, triggering a berserker frenzy in his sons that drove the bewildered Death Guard out of the spaceport. The Khagan was carried out of the spaceport on a Leman Russ, where he was met by Ilya Ravallion. She sensed a spark of life within his broken and ravaged body and immediately had him taken to Malcador, who set his adepts to the task of healing the primarch.

Within the walls of the Palace, chaos reigned. As walls fell and city blocks were blasted into ruin, hordes of civilian refugees and Imperial Army units fled toward the illusory safety of the innermost districts, with the World Eaters and Sons of Horus at their heels. Some garrisons made lonely last stands, hoping to tie down the traitors as long as possible, while others collapsed and were overrun. As Dorn faced the inevitable, he summoned First Captain Sigismund and gave him a simple order: "Hurt them." As Sigismund made for the battlefield, he was greeted by Khalid Hassan, who brought him the Black Sword, an ancient and potent relic weapon forged in Earth's pre-Unification era. Sigismund took up the blade and went out to fulfill his father's orders, sworn now to fight for the Imperium as it would become, not as it had been. He cut down hundreds of traitor champions in single combat. Rumors of the warrior known as the "Black Sword" or "the Emperor's Champion" began spreading across the Palace, heartening loyalists and demoralizing the traitors. Many on both sides sought him out, either to join him or to kill him. Sigismund finally encountered Kharn, who challenged him to a rematch. Sigismund's cold, impassive fighting style disturbed the World Eater, who furiously tried to provoke a reaction in the First Captain. Unshaken, Sigismund fought Kharn to a standstill and cut him down, but not before the World Eater saw the truth of things in a rare moment of lucidity: Sigismund was the herald of a new kind of Imperial warrior, of a legion of fanatical, stoic, single-minded zealots whose relentless fury and inability to countenance defeat would wreak untold misery on a galaxy already groaning under the weight of aeons of anguish.

Meanwhile, Euphrati Keeler, who was now loose and alone in the ruins, used Sigismund as the inspiration for a new kind of army. Rallying the masses of civilian refugees and Army stragglers, she forged them into a militia armed with tools, a few lasguns, and their faith in the Emperor and sent them forth to fight the Traitor Legions. Though a hundred of them might fall in exchange for one traitor, Keeler regarded it as a fair exchange, for there were hundreds of thousands more to take their place. Garviel Loken, upon finding Keeler, was dismayed by her harsher, more brutal mindset. She justified it to him by arguing that this was the kind of army the Imperium would need in the future: an army of millions, even billions of humans, united by their unwavering faith in the Emperor and their hatred for the alien, the mutant, and the traitor.

Final Stand of the Eternity Gate

Although the Lion's Gate Spaceport has been retaken, the situation continues to deteriorate for the loyalists. With the palace defenses all but collapsing due to the breach at the Ultimate Wall by Legio Mortis, the loyalists have been forced back to the Sanctum Imperialis. Jaghatai Khan is incapacitated, leaving Shiban Khan in command of most of the White Scars at the Spaceport. Help is nowhere to be seen and won't be coming anytime soon- Sanguinius has ordered Corswain's men to stay put and defend the Astronomican to guide the way for Guilliman and Johnson, who're still a week out. The traitors meanwhile have victory in their grasp. The Emperor's psychic shield is at risk of failing due to Magnus The Red's psychic assaults in the Webway. The only thing truly going in the loyalists' favor is the degradation of Horus' armies into an uncoordinated mass known as The Horde. With Rogal Dorn and his retinue now besieged at the Bhab Bastion, only 70,000 loyalists stand between the traitors and the Imperial Palace itself. This force is largely composed of Blood Angels led by Sanguinius and Imperial Army, but some Imperial Fists, White Scars, loyalist Mechanicum units, and Legio Ignatum were present as well to muster on the Delphic Battlement. Under orders by Horus for the first time in weeks, the traitors are given a single order: capture the Eternity Gate at dawn.

Before attacking, they hoisted the living bodies of loyalist prisoners on whatever could hold their tortured forms. The Reaver Titan Daughter of Torment from Legio Mordaxis then marched forward and opened its power claw to reveal Blood Angels Captain Idamas. Idamas was fatally wounded after being pinned to the claw by 7 spears. Following these acts of barbarity they issued Horus' offer: flee the coming battle and be granted a pardon by the (soon to be) new Emperor of Mankind, or die. To punctuate the offer and insult, the Titan began closing its claw to slowly crush Idamas to death. However, Skitarii Transacta-7Y1 was ordered to snipe the captain by Sanguinius to put him out of his misery and deny his captors the satisfaction of such a murder. Sanguinius then turned to the defenders and gave a rousing speech so awesome it inspired and/or shamed all of them into standing their ground. After that, he flew to the Daughter of Torment and cut off the fucker's head. With that, the battle was joined.

As the guns of the Delphic Battlement unloaded, the Chaotic horde zerg rushed the loyalists. Many were mowed down, but sheer weight of numbers allowed them to reach the wall. A Khornate Warlord Titan docked with the Delphic wall to vomit its World Eater cargo from its mouth. The battle quickly descended into a frenetic melee, which the Bloodthirster Ka'Bandha charged into. Ka'Bandha vowed to kill 500 Blood Angels in front of Sangy, and got pretty close before Hawk Boi swooped in to save his sons. In a lopsided airborne fight, the Bloodthirster got his back broken with the hilt of Sanguinius' sword and cast down. He was then consumed by lesser demons who preyed on his weakness. Despite the loss of this greater demon, it wouldn't stop the uncountable horde that was fast approaching. Demons were even manifesting into the Sanctum Imperialis itself. Tribune Diocletan Coros ordered the closure of the Eternity Gate as a response, but Legio Audax Titans kept it open with their Ursus Claws to force the doors open. As Sanguinius moved to cut the chains, Angron made a superhero (villain?) entrance under orders from Horus to kill Sanguinius.

The two Primarchs engage in a vicious duel that sees Sangy delivering a variety of normally fatal blows to Angron with skill and grace. Unfortunately, a tired and weakened Sanguinius is unable to deliver any punishment that Angron can't tank by virtue of being a fuckhuge Demon Primarch, and Angron proved to be no slouch in the fight either. After numerous abortive attempts to fight while airborne, Angron decided to change tactics and fight on the ground while getting Sanguinius to fight him. Angron slaughtered many Blood Angels to force his brother's attention. The two duelled again, and the exhausted Sanguinius began losing ground. Both Primarchs knew the fight would not (and in the case of the Great Angel, COULD NOT) go on much longer. Angron let Sanguinius stab him to get close and begin crushing his throat, while in the same motion stabbing Sanguinius' gut with the Black Blade. Of course, the ole 'tank a stab to get in close and deliver a fatal blow' trick is not unique to Angron and Jaghatai Khan. Sangy had the same idea and used the opportunity to pull out the Butcher's Nails from Angron. This somehow caused enough pain for him to beg Sanguinius to stop, to no avail. Both nails and brains were ripped out and thrown away, before Angron's physical incarnation was finally killed and he was banished to the Warp. Khorne laughed at the sight, while Angron's less amused sons completely lost it and began teamkilling en-masse.

Meanwhile, below the Palace, Vulkan was dispatched into what was left of the human Webway project to stop Magnus the Red's assault on the Emperor's psychic defenses. Despite Magnus employing a variety of horrifically lethal magic tricks on Vulkan, it's all futile against a perpetual Primarch. Magnus is slowly worn down between the constant strain of using magic and weathering endless assaults by Vulkan. In a final gamble to buy time or convert his brother, Magnus brings the both of them into his mind to play out his experience and give his motivations. Vulkan has none of it, spitting nothing but facts (including some that even Magnus is wondering how Vulkan could've known) at his brother's persecution complex and hubris. Of particular note is that Magnus only imagined being offered a costly path towards redemption by the Big-E, when in reality he was told to kick sand and GTFO. Regardless of why, the result is the same: Magnus retreats to that familiar feeling of self-righteousness and dances to the tune of Chaos. With nothing left to argue about, Vulkan smashes Magnus into paste while Magnus creates one last uber spell to unmake Vulkan molecularly. One is sent back to the warp, and the other walks away.

With these two events, the Chaos forces were stopped just outside the now-sealed Eternity Gate. The loyalists fled inside and licked their wounds. While the Great Angel regarded his wounds, he and Dorn gave their final goodbyes. The White Scars reactivated the anti-orbital defenses at the Lion's Gate Spaceport and laughed at the bastards in orbit before tearing into them with all the firepower their defenses had. Roboute Guilliman sent word that he and his allies were 1 week away, but Lotarra Sarrin intercepted the message. The situation for both sides became truly desperate. Traitorous mortal crews (and many of the Thousand Sons remaining on Terra) can no longer maintain physical forms that obey the laws of physics, unit cohesion and the traitors are no longer on speaking terms, and their flanks are eagerly awaiting a well-deserved pounding from the inbound loyalist relief fleet. With nobody left to rely on and only one last chance at victory, Horus would have to lower the shields and force the Emperor to come to him. The loyalists unfortunately don't know any of this, only being aware of the fact that the Grim Reaper will be taking them out to lunch very soon. And thus the die is cast.

Duel of the Emperor and Horus

If you haven't seen this image yet, you must be new. Like, really fucking new.

Like with any truly epic event, the siege only ended with the most motherfuckingest duel in the entire 40k fluff: the Emperor of Mankind against Horus, the most favoured of the Primarchs and the living avatar of the Chaos Gods. If the Horus Heresy was the most important of a series of events, if the siege was the single most epic of those events, then the duel is the defining moment of the fluff and affected everything else that came after it.

Dorn, Sanguinius, and the Emperor, along with what forces they could bring, teleported aboard Horus's battlebarge to force an end to the conflict. It was Sanguinius who found Horus first. Horus hits 3 times, wounds 2.667 times, 1.33 after saves and IWND takes that down to 1 wounds at start of next turn. Sanguinius doesn't get the charge, so he hits 4 times, wounds 3.556 times, 1.185 after saves and IWND takes that down to 0.852 wounds at start of next turn. The angelic Lord of Baal, beloved of the Primarchs, died just as the Emperor arrived.

During their ensuing epic and titanic duel, the Emperor could not bear to kill his most beloved son. So, Horus had managed to mortally wound him (despite the Big E being a nigh-unkillable Perpetual) and would have finished him off, if not for the intervention of one Perpetual Guardsman (Oll Perrson/Ollanius Pius)/Imperial Fist/Custodian. He jumped in front of Horus as he was about to strike the final blow, and was flayed with a glance. The Emperor, witnessing how far his most favored son had fallen, decided "Fuck this" and focused all of His remaining psychic power into one massive and final Kamehameha that LITERALLY DELETED HORUS'S SOUL FROM EXISTENCE!

Although the Emperor managed to win and kill Horus, he was so badly wounded in the end he needed to be on 24/7 life support just to survive. So really when you come down to it, it was a draw; Chaos had been stopped then but only at an unthinkable cost to the Imperium.

/tg/ Connection

What, besides the fact that it's the most important event in the 40k universe? Fine.

The Siege of Terra is also the theme for the Horus Heresy board game, in which you reenact the Siege itself. There. Happy? (Not really.)

The fa/tg/uy's explanation of the Siege Of Terra (for Dummies and BL Editors)

Some serious Daddy problems.

The main rule of warfare: As the number of combatants increases, the resemblance to complete uncontrolled insanity approaches infinity. And then you have to take into account the terrain...

Basically, you start with a planet that's been nuked, polluted, and generally lived in for a few hundred thousand years too long. Everyone on it is fighting everyone else, constantly. Your basic unit of land is the Bunker, Vault 101 style. There isn't any natural plant life left so all the oxygen is made in vats with the food. Luckily this means you can build anywhere that isn't intensely radioactive and hence fight over those areas. Get Mega-City-One, nuke it, and rebuild it a few times, and then you start to understand.

Then the Emperor comes along and manages against all odds to conquer the place. Suddenly everyone isn't killing and dying all the time, and a population boom happens. So Emps organized the largest set of public works since the first colony ships. He rebuilds huge areas of the planet and creates the Imperial Palace, the Astronomican, and a buttload more of cool shit besides. And what he gets is effectively one giant city, the second largest (after Commorragh) in the universe. "Huge" just doesn't do it justice as a description. Neither does "labyrinthine", "overpopulated", or "Gothic nightmare". And this New Terra was mostly just thrown over the original foundations of whatever was there like a pile of gold bricks onto a rat maze. There are bunkers and emplacements still around that date back to the War Against The Men of Iron and even before.

Then the Heresy came, and the Emperor says to Dorn "Fortify this fucking madhouse". So now everything that didn't have a gun emplacement before does now, everywhere. Dorn walled in half the doors and windows, put hundreds of AA batteries on every roof, filled entire rooms with concrete just for a bit of reinforcement, built hundreds of miles of trenches, redoubts, bastions, emplacements, and backup walls, conscripted half the population into the army (and half of that into the engineer corps), and generally panicked because all of this would only ever be necessary if the solar system's defenses (the best in the galaxy bar none) have failed.

Then Horus arrives in orbit. He's punched through the space defenses at massive cost, but the war in space is far from won, and the Palace is just a flat no-fly zone, so he can't just pick and choose landing areas. So he bombards everything his ships can reach, fills the sky with Drop Pods, and tries to march on it.

This is when Rule #1 kicks in and everything immediately gets megafucked for both sides. Ruined streets, trenches, and bunkers make navigating a nightmare, communications are somewhere between impossible and actively detrimental, drop pods and gunships are shot down immediately or land off-target, plans and backup plans fall apart in seconds, daemons run amok, and the Primarchs are either constantly trying to out-Tactical-Genius each other or are too in the thick of it to relay any commands, so no one has a fucking clue what's actually going on in the big picture. It's Stalingrad on a continental scale, but without even the merest hint of sanity and a thousand Space Marines charging into every breach. The inclusion of cackling daemons, rampaging renegade Guardsmen and abhumans, and bellowing daemon engines doesn't help the situation, nor does the fact that the guy ostensibly in charge of the Siege (Horus) is growing increasingly detached from reality.

So it takes roughly 10 minutes of this menial bullshit for a load of the Chaos forces to get bored and just decide "Fuck It, Let's Just Wreck The Place". So now everything makes even less sense: entire Legions are ignoring sensible objectives to go on the Chaos Marine equivalent of a bender. The Emperor's Children and the Night Lords rape, murder, and pillage the civilians of Terra so hard that even 10,000 years later they still live in fear at the memory, while the World Eaters are tearing around and hacking and slashing at anything they think might bleed. Only the Iron Warriors, the Death Guard, and the Sons of Horus are wholeheartedly tearing at the Palace, dedicated to rubbing it in Dorn's face like a bitch no matter what (and even then, the Iron Warriors would ultimately decide "fuck this" and leave). And to the horror of the loyalists, they're still succeeding. Brick by brick, the greatest military stronghold in the galaxy is falling.

Which sounds great for Chaos were it not for the simple fact it wasn't falling quickly enough. It was taking days to advance inches at massive cost, and Guilliman was en route with reinforcements, with Russ and the Lion and the remains of their Legions right behind him. If the siege wasn't ended before they got there, the traitors would likely lose. So Horus put all his cards on the table and lowered his battle barge's shields, goading the Emperor (who didn't know about the reinforcements - or maybe he did and was enacting a much greater scheme, see below) on board to hopefully kill him and force the defenders into a rout. Everything else is history.

The short story "The Board is Set" seemed to indicate that the Emperor and Malcador knew about the reinforcing loyalists from at least the beginning of the siege and were fully aware of the siege's outcome up to and including the Emperor's ascension to the Golden Throne, possibly even seeing the future all the way to the events of the Era Indomitus. It also seemed to imply that Horus lowering his shield may have been so he could teleport down and attack the Emperor, not realizing it was Malcador on the throne. Possibly the most epic level of Just As Planned.