Schism of Mars - War Comes to Mars: The climate on Mars was full of discontent during this tumultuous time in the days just before Horus openly declared his rebellion against the Emperor. There were tense relations between the various Mechanicum Magi who governed Mars with sporadic outbreaks of espionage and violence committed against the various forge cities that represented the primary sociopolitical units of Mars. There were even unconfirmed suspicions that the various Titan Legions of the Collegia Titanica, the most potent military forces available to the Mechanicum, had already secretly chosen sides in case of a potential conflict.Indeed, a large faction of the Martian Mechanicum led by Fabricator-General Kelbor-Hal had come to believe that the Emperor was a false idol and not the true Omnissiah promised by the Machine God, who had yet to reveal himself. More importantly, Kelbor-Hal harboured great resentment against the Emperor for His conversion of Mars into little more than a weapons factory to supply the forces of the Great Crusade and His ban on certain types of technological research, particularly artificial general intelligence.At the outset of the Horus Heresy, the Warmaster Horus sent Regulus, a Mechanicum representative who had already thrown in his lot with the Warmaster, to Mars to secure the tentative support of Kelbor-Hal. Regulus convinced the Fabricator-General of the Warmaster's resolve to support increased autonomy for the Mechanicum against the autocratic rule of the Emperor.As a show of his appreciation for the Fabricator-General's support and of the advantages of siding with the Traitors, Horus provided the access codes to Kelbor-Hal that allowed the Tech-priest to open a repository of forbidden knowledge known as the Vaults of Moravec, which the Emperor had ordered sealed two Terran centuries earlier -- for they contained innumerable artefacts of technology that had been fashioned or corrupted by the malign power of Chaos. But their dark bargain was struck, and the Fabricator-General accepted Horus' proposal and joined forces with the Warmaster, assisting the Traitors with all of the technology of Mankind at his disposal.When this repository was reopened, there was all manner of forbidden arcane knowledge and weaponry that had obviously been tainted by the corrupting influence of Chaos stored within. Soon the corruption spread throughout the forges and temples across the Red Planet as scrap code -- Chaos-contaminated digital source code that was infected with an arcane computer virus -- infested the logi-stacks and Cogitator (computer) archives of the Mechanicum, causing literal Chaos to emerge in any Cogitator system that was networked to one of its infected counterparts.As a result of the scrapcode infestation, communication across the world and off-planet was severely disrupted and many essential industries were sabotaged. A period of general confusion followed, which the Fabricator-General and his allies used to marshal their forces, intent on making sure the whole of Mars was firmly under their rule.This proved to be more difficult than they had at first anticipated. Several regions of Mars remained relatively uninfected by the scrapcode, insulated against the assault by their early adoption of a new, far more secure digital information network technology called the Noosphere. Among these regions were the Forges of Koriel Zeth, Ipluvien Maximal, and Fabricator-Locum Zagreus Kane, who would go on to become the leaders of those Tech-priests who chose to remain loyal to the Emperor and resisted being drawn into Kelbor-Hal's so-called "Dark Mechanicum."While the opening shots had already been fired when the Kaban Machine of Lukas Chrom destroyed a plasma reactor complex belonging to the Loyalist Adept Ipluvien Maximal, it still took a short while before open civil war began.As he still required some pretense to unleash war against the Loyalists, Kelbor-Hal and his allies attempted to provoke those unwilling to join them, employing various acts of sabotage, assassination and outright aggression to eliminate those who were unwilling to join their cause. One example of these tactics was when the Dark Mechanicum-aligned Legio Mortis attempted to goad the Legio Tempestus into opening fire first by entering Tempestus territory and refusing to answer hails.Eventually the pretense Kelbor-Hal required was given to him by the Techno-Magi Koriel Zeth, the Mistress of the forge known as Magma City, when she declared she no longer believed the Machine God existed, though she remained loyal to the Emperor and His goals for Mankind, as technology was developed through the application of science and reason, not blind faith.The Dark Mechanicum used her apostasy against the sacred doctrines of the Cult Mechanicus to declare her and her supporters Hereteks and unleash an assault against Magma City, bringing war to Mars as those pledged to Kelbor-Hal and Horus attacked those determined to remain allied to Terra and the Emperor. Magma City would soon become a focal point in the struggle for those among the Mechanicum who remained loyal to the Emperor as the Omnissiah and His Imperium.Later histories would record that the first blow of the Martian civil war was struck against Magos Mattias Kefra, whose forge in the Sinus Sabaeus region was housed within the Madler Crater. Titans of the Legio Magna marched from the southern Noachis region and within solar minutes had smashed down the gates of Kefra's forge. Howling god-engines daubed in red, orange, yellow and black, and decorated with flaming horned skull devices, ran amok within the high walls of the crater, crushing everything living beneath them and destroying thousands of standard years of accumulated wisdom in a fury of fire.Vast libraries burned and weapon shops that served the Imperial Army regiments of the Solar Guard were reduced to molten slag as the indiscriminate slaughter continued long into the night, the Magna Legion's trumpeting warhorns sounding like the atavistic screams of primitive savages.Further north in the Arabian region of Mars, the great god-engine fabrication yards of High Magos Ahotep in the Cassini Crater were struck by a hundred thermonuclear missiles launched from the atomic silos secreted within the isolated peaks and mesas of Nilo Syrtis. The explosions of the forbidden weapons filled the four hundred and fifteen kilometer diameter of the crater with seething nuclear fire, and sent conjoined magma-streaked mushroom clouds soaring nearly seventy kilometres into the sky.Along the borders of the Lunae Palus and Arcadia regions, what previously had been simply heated debate between the partisans of the Emperor and the Warmaster erupted into outright warfare as Princeps Ulriche of the Death Stalkers unleashed his god-engines upon the fortress of Maxen Vledig's Legio Honorum.Caught by surprise, the Legio Honorum lost nineteen Titans in the first solar hour of battle, before withdrawing into the frozen wastes of the Mare Boreum and seeking refuge in the dune fields of Olympia Undae. Their calls for reinforcement went unanswered, for all of Mars was tearing itself apart as the plague of war spread across the planet in a raging firestorm.Amid the Athabasca Valles, the war machines of the Legio Ignatum and the Burning Stars Titan Legion fought in bloody close quarters through the teardrop landforms caused by catastrophic flooding in an earlier, ancient age of the Red Planet. Neither force could gain the advantage, nor could either claim victory, so after a night's undignified scrapping, both withdrew to lick their wounds.At Fabricator-Locum Kane's forge, the Mondus Occulum, the outlying forge Cogitators and logic engines had clogged with corrupt data, howling ghosts of sourceless machine-noise and dangerous code packets of infected algorithms that many of the most advanced protective Aegis Protocols were helpless to defeat. Only Kane’s swift action to shut down the Input/Output highways and the fact that the vast majority of his systems had recently been upgraded to take advantage of Koriel Zeth's revolutionary system of noospheric data transference had spared them the worst of the attack, for an attack it surely had been.Kelbor-Hal himself soon unleashed his twisted Skitarii and Combat Servitors on the Forges of Ipluvien Maximal. Maximal was able to repel the first wave of attackers, but within solar hours he was totally besieged by unique Ordinatus war engines. At the Herschel impact basin of the Mare Tyrrhenum, 900,000 Skitarii and Protectors clashed in a bloody melee that continued until nearly all were dead.The single greatest loss of life in a single battle of the conflict took place at the Ismenius Lacus forge city after Dark Mechanicum forces unleashed Virus Bombs on the settlement, killing 14 million people within only solar minutes.The apocalyptic conflict was not limited to the surface of Mars, and high above in the planet's orbital shipyards Traitor voidships exchanged fire with their Loyalist counterparts after forcing the vessels of the Battlefleet Solar to withdraw. During one of these exchanges, the Ark Mechanicus Mechanicum Glorian was destroyed by Dark Mechanicum Frigates and crashed into the Basilica of the Blessed Algorithm on Mars itself. The crash annihilated millions of square kilometers and killed billions of people across the planet.Magma City soon became a focal point for the resistance, with both the Legio Tempestus and the Knights of House Taranis coming to Koriel Zeth's aid. Defending against the Chaos-fuelled power of the Dark Mechanicum proved a difficult business and soon not only Zeth's forge, but those of Maximal and even Kane found themselves effectively surrounded and besieged by their enemies.A vicious battle erupted at Magma City, led by the Legio Mortis and its Imperator-class Titan Aquila Ignis. However the Traitor Titan Legion's attack on Magma City was blunted when lava overran the traitor ranks, and most of the Titans of the Legio Mortis (including the Aquila Ignis) were destroyed by the Legio Tempestus. But despite the victory at Magma City, the situation remained dire for the outnumbered and outgunned Loyalist forces across the planet.Similar instances of open warfare eventually erupted all across the Red Planet as Martian forces, both civilian and military, fought one another in a deadly and escalating civil war in which the destruction unleashed on Mars mirrored that unfolding in the wider galaxy between Loyalist and Traitor forces.