The Indomitus Crusade was the standard-century-long Imperial Crusade led by Lord Commander of the Imperium Roboute Guilliman from Terra during the period known as the Noctis Aeterna in the early 42nd Millennium. Its purpose was to defend and reclaim those regions of the Imperium of Man threatened by the surging Forces of Chaos and the threats of xenos such as the Orks, Tau, Drukhari and Tyranids in the wake of the 13th Black Crusade and the birth of the Great Rift in 999.M41. The Crusade lasted into the early second century of the 42nd Millennium, coming to an end at the Battle of Raukos. At its completion, Guilliman declared the Crusade over during a great triumphal review and dispersed its military elements across the Imperium, reinforcing many worlds with new Chapters of Primaris Space Marines.
In the wake of the Indomitus Crusade, the Imperium was stabilised from imminent collapse in the face of myriad threats, though there was no clear victory over those forces that still sought to exterminate Mankind's light from the galaxy. With the formal end of the Crusade, Guilliman finally returned home to the Realm of Ultramar with Imperial reinforcements. He met his brother, the Daemon Primarch Mortarion, in battle to prevent him from adding Ultramar to those worlds already claimed by the servants of the Plague God Nurgle during the so-called Plague Wars.
When the hour was blackest and the Imperium's doom seemed at hand, there came a shining light, a beacon in a galaxy gone dark. This was what Roboute Guilliman called the Indomitus Crusade -- the gathering of a vast coalition of Imperial forces that took the fight to the enemy and brought back a sliver of hope to hundreds of besieged planets.
Second Battle of Terra
After the fall of the Noctis Aeterna and the birth of the Great Rift, the citizens of many Imperial worlds looked up with dread at that which pulsed unnaturally above them, fearing what might descend from the stars. Not all were cowed, however, and some endeavoured to leave their isolated planets and reconnect with the wider Imperium. In the wake of the worst Warp Storms recorded in Imperial history, over a dozen expeditions were launched, amongst them the Aquila Crusade and the attempt to reclaim the Donlar Sector by the Revilers Spearhead. Few of these ventures fared well, and some, like the ill-fated Charon Crusade, proved disastrous. There was one undertaking, however, that did more than just succeed.
While the Blackness fell across whole segments of the galaxy, Roboute Guilliman refined his grand strategy upon Terra. After standing before the Golden Throne at the conclusion of his Terran Crusade, the Primarch had emerged with renewed sense of purpose. Not long after the High Lords of Terra declared him Lord Commander of the Imperium, Guilliman called for action, ordering the mustering of a mighty armada. Even as the forces of the Indomitus Crusade gathered, its numbers including Primaris Space Marines from the Ultima Founding, Guilliman's operation was interrupted by a daemonic incursion in service to the Blood God Khorne that erupted out of a sudden Warp Storm. While many panicked over the breach in Terra's multi-spectrum shield defences, the Primarch led the counterattack himself in what became known as the Second Battle of Terra. None could stand before the ﬂame-wreathed Sword of the Emperor, and together the Adeptus Custodes, Sisters of Silence and many companies of Ultramarines dismantled the Khornate threat and banished it back to the Empyrean.
On Terra, elements of the Adeptus Custodes and a contingent of the Silent Sisterhood pledged to join Guilliman's new Crusade. They were not alone. Upon nearby Mars, Archmagos Dominus Belisarius Cawl had unlocked his vaults, producing from stasis the fruits of his longest labours -- the Ultima Founding. To complete the full deployment of his long-prepared masterworks would take solar months. Cawl's own ﬂeet joined the Primarch, headed by his freighter-hulk, Zar-Quaesitor, a mech-ark class ship that carried within its massive hull a vast number of Primaris Marines still in stasis hibernation. The Archmagos brought with him several armies of Skitarii and Legio Cybernetica, alongside three lances of Knights from House Taranis. With Warp energies ﬂooding the galaxy, the reach of Terra's astropathic choirs was greatly reduced, yet many loyal defenders heeded that mustering call. These included a number of Astra Militarum forces and over a score of Space Marine Chapters. None volunteered more quickly than the redoubtable Imperial Fists. To transport the Imperium's soldiers came fully half of the Imperial Navy's Segmentum Solar ﬂeet. Later, en route to the Indomitus Crusade's many destinations, other Imperial forces joined, eager to bow their heads in respect before the living legend that was the fabled Ultramarines Primarch.
Bringing the Emperor's Light
With the Astronomican still ﬂickering sporadically, the Indomitus Crusade risked only short jumps through the Warp. They clove a path through system after system. Where worlds could be saved, Guilliman unleashed the full might of his powerful armies. Daemon hordes were driven back from Gathalamor, the Drogos System and the world of Tallarn. In the Lhorm Reaches, the Brass Tyrant was cast down. The entire population of Ophelia VII was freed from the enslavement of the Tyrant of Blueﬂame, although the Greater Daemon escaped the Emperor's justice. The Befouled Beast that claimed Caster was met in battle by Guilliman himself. Although the monster towered over him, it was the Primarch who emerged unharmed from that duel. Word of the Crusade's approach alone was enough to quell the rebellion on Necromunda.
By the time the Imperial forces reached Catachan, all followers of the Dark Gods there had already been defeated by the local Astra Militarum regiments. The Crusade halted there all the same for reinforcement. Despite heavy losses, the Indomitus Crusade was larger when it departed Catachan than when it first left Terra.
As the Indomitus Crusade worked its way outwards from Terra, the worst eﬀects of the Noctis Aeterna were already lifting across many sectors. Although Warp Storms still drifted out of the Great Rift, the Emperor's Light was slowly burning away the formless murk of the Warp throughout the galactic south. Many citizens that survived the cruel oppressions of daemonic torturers saw divine correlation between the two events. Those that glimpsed the Primarch firsthand whispered that they had seen the Emperor Himself, as if legends from a golden age of myths once more strode amongst them. Vidfeeds and astropathic visions spread still further, allowing hope to rekindle even upon planets whose plight was desperate.
Not all was triumph and glory, however. The Crusade came to many worlds that were beyond salvation. Where there was no hope, Guilliman sought instead to bring vengeance. There could be no saving the Hive World of Bhundar from the bubonic taint that covered it, but once cauterised with cleansing fire, the Warp disease spread no further. The daemonic rituals held atop the mouldering ruins of the Cardinal World Gloriphia were not just halted but annihilated, and there the daemonic ichor ran in rivers. Not all could be avenged, however. The initial combat drop into Secundus Terra suﬀered ambushes and catastrophic malfunctions, having been lured into a terrible trap by the Alpha Legion. Although it pained him to do so, Guilliman made the difficult decision to pull back, skirting the whole Primagenesis System, as he could not aﬀord to become bogged down in a long war of attrition. The Crusade's journey later saw it encounter dozens of star systems in which countless Imperial citizens were left in thrall to the Dark Powers. This was a bitter reality for Roboute Guilliman, and even if the Ultramarines Primarch was given to dwelling on the Imperium's misfortunes, there would be no time to do so.
Seeds of Hope
As the Indomitus Crusade penetrated deeper into the galaxy, Archmagos Cawl kept his automaton workers on overdrive, risking meltdowns with their accelerated speeds. Locked deep in the labyrinthine holds of Zar-Quaesitor, thousands of Primaris Space Marines -- some comprising entirely new Chapters and others designated as reinforcements for existing ones -- were awakened out of stasis and made ready to join the fray. On battle-scarred Rynn's World, the arrival of the Indomitus Crusade broke the daemonic legions of the Daemon Prince Rhaxor. After the fighting was done, the Crimson Fists marvelled at the return of Roboute Guilliman, but were even more grateful for the arrival of Primaris Space Marines bearing their own heraldry. Here were warriors whose genetic composition was closer to their own Primarch, Rogal Dorn, than had ever before existed. For his raw material, Cawl had selected warriors of Terra, and had taken them only a few generations after the original Imperial Fists had been created by the Emperor. Indeed, some had been held in stasis since the days of the Great Crusade; a few of the Primaris Space Marines could recall having seen Rogal Dorn himself.
Many Chapter Masters welcomed their Primaris brethren into their ranks, accepting the new reinforcements gladly. Others, though, viewed these new creations with suspicion or outright hostility, claiming that the Emperor's work should never have been meddled with by mere mortals.
Fortunately, the Emissaries Imperatus, a Shield Host of the Adeptus Custodes, the elite bodyguard of the Master of Mankind, stepped forward to intercede, stating that the gift that was the Primaris Marines was the will of the Emperor. As "Heralds of the Golden Throne," they had accompanied Guilliman's Crusade, many of them taking to the air as Vertus Praetors, the quicker to deliver messages of reinforcement to the embattled Space Marines. The presence of the Adeptus Custodes also ensured that even the most traditional Chapters accepted the Primaris warriors into their ranks. One does not decline a gift from the Emperor's own hand, after all.
Again and again the Crusaders watched the same tale unfold. When those of the Ultima Founding were brought before their Chapters, it was like a meeting of brothers separated at birth. Arriving at a time of great darkness and upheaval, the new transhuman warriors' strength was welcomed. Such unusual reunions were repeated on many Astartes worlds, including Chogoris, Ultramar and Baal, where the Crusade arrived even as the proud Sons of Sanguinius were making what they thought would be their last stand against the Tyranids of Hive Fleet Leviathan during what became known as the Devastation of Baal.
Despite cleaving a wide path through the darkness that beset the Imperium, the Indomitus Crusade began to break down. When the vast holds of the Zar-Quaesitor were at last emptied, Archmagos Cawl departed, for he had many more secret vaults to activate in order to complete the Ultima Founding. Once deployed, the new Primaris Chapters -- such as the Rift Stalkers or the Umbral Knights -- remained after the initial conﬂicts were won, seeking to consolidate the Crusade's gains; in many cases, they did this by establishing their own new Chapter planets. In this way, the Crusade not only freed worlds from the tyranny of the Dark Gods, but also strengthened their defences against further attacks that were sure to come. Finally, Roboute Guilliman could no longer delay responding to the distress signals coming from his Chapter's own home Realm of Ultramar, which was itself once more besieged. All their triumphs were but a sliver of light piercing the ink-black void, their many campaigns unable to reach the vast number of imperilled planets -- yet it was a start. Later it was said that during the darkest hours the Imperium had endured since the Horus Heresy, it was the Indomitus Crusade that gave Mankind the hope to persevere.
The Indomitus Crusade would reach its final end over a standard century after its beginning at the dawn of the second decade of the 42nd Millennium at the Battle of Raukos. In the aftermath of the victory against the Forces of Chaos at the Pit of Raukos, Guilliman decided to disperse the Indomitus Crusade by holding a triumph much like the one the Emperor of Mankind had held in the wake of the Ullanor Crusade during the final days of the Great Crusade. At the ceremony 20,000 Primaris Space Marines, 40,000 standard Space Marines, 3 Sisters of Battle convents, Skitarii Legions, Titans, Imperial Knights, Adeptus Custodes, Sisters of Silence, and two million male and female soldiers and voidsmen of the Astra Militarum and Imperial Navy were present. Guilliman announced his decision to disperse the Crusade throughout the Imperium and that he would next turn his attention to helping his Realm of Ultramar defeat the forces of the Death Guard Traitor Legion and the servants of Nurgle in the Plague Wars.
- Battle of Lion's Gate - Roboute Guilliman defeated a massive daemonic assault by the forces of Khorne upon the Imperial Palace. After the Battle of Lion's Gate, sometimes remembered informally as the "Second Battle of Terra," the High Lords of Terra realised that no place in the Imperium was now safe from an assault by the Archenemy.
- Devastation of Baal - With the arrival of Roboute Guilliman's Indomitus Crusade, the Blood Angels and their Successor Chapters were successful in fending off the great assault of Hive Fleet Leviathan upon their homeworld of Baal. The remainder of the Leviathan is largely consumed by a Warp Storm and a great assault of Khorne daemons led by the Blood Angels' ancient foe, the Bloodthirster Ka'bandha.
- Battle of Raukos - The Battle of Raukos was a two-pronged assault upon the world of 108/Beta-Kalapus-9.2 and the Warp rift known as the Pit of Raukos in Wilderness Space. The Loyalist forces quickly overwhelmed the allied Traitor Legions -- including the Word Bearers, the Iron Warriors and the Black Legion -- using the strategic location of the Warp rift to carry out assaults upon the surrounding Imperial worlds. This victory marked the end of the Indomitus Crusade and the start of Guilliman's involvement in the Plague Wars.
- Roboute Guilliman
- 13th Black Crusade
- Ultramar Campaign
- Terran Crusade
- Noctis Aeterna
- Imperium Nihilus
- Plague Wars
- Codex Adeptus Astartes - Space Marines (8th Edition), pp. 20-21
- Codex: Adeptus Custodes (8th Edition), pg. 27, 32
- Dark Imperium (Novel) by Guy Haley
- Warhammer 40,000: Rulebook (8th Edition), pp. 50-53