Rangdan Xenocides

The Rangdan Xenocides
Date	ca. 839.M30 - ca. 930s.M30
Scale	Sector-wide
Theatre	The Halo Stars
Status	Imperial victory
Belligerents
Rangdan Cerabvores	Imperium of Man
Commanders and Leaders
Unknown	Emperor of Mankind, Leman Russ, Lion El'Jonson
Strength
Rangdan Cerabvores, Rangdan Osseovores, Slaugth Murder-Minds, Rangdan War-moons	Dark Angels Legion, Space Wolves Legion, War Hounds Legion, Death Guard Legion, Alpha Legion, II Legion, V Legion, XI Legion, XIV Legion, Legio Gryphonicus, Legio Vulturum, Legio Kydianos, dozens of other Legio Titanicus Legions, Knight House Malinax, Knight House Orhlacc, Xanite Mechanicum Taghmata Forces, Centurio Ordinatus, Ordo Reductor
Losses
Unknown, probably total	Massive losses among Imperial expeditionary forces, entire Titan Legions and fleets destroyed, possibly two Legiones Astartes destroyed. At least 80,000 Astartes casualties. uncounted millions of Imperial Army casualties.
Outcome
Elimination of the Rangdan threat to the northern Imperium; continuation of the Great Crusade; depletion of the Dark Angels and Space Wolves Legions; Ultramarines become the largest Space Marine Legion

The Rangdan Xenocides were collectively the largest and nastiest fight the Imperium of Mankind faced during the Great Crusade. This was a conflict so horrendous that it swallowed entire expeditionary fleets and Titan legions, nearly crippled the Death Guard, the Dark Angels, and the Space Wolves, and saw dozens of worlds laid waste. Most interestingly, it may or may not also be the reason that the II and XI Legiones Astartes were wiped from all Imperial records.

The Campaign

The Xenocides began sometime in the late 860s.M31, around the time that the Imperium was entering the Eastern Fringe of the galaxy. As they were expanding toward the Halo Stars, they drew the attention of the Rangdan Cerabvores, a mysterious and hostile xenos species who decided to tell these upstart humans to get the fuck off their lawn. Unfortunately for the Imperium, they had the will and the technology to make it happen, and would in fact prove to be the single greatest threat to its existence up until Horus's little temper tantrum.

Information on the Xenocides is scarce, coming from multiple sources and often referenced in vague mentions. This appears to have been intentional, as the Dark Angels deliberately purged all knowledge of the Rangda and the wars fought for the good of the Imperium. No actual descriptions of the Rangda themselves remain, though enough secondary details survived to paint a grim picture: they were towering and monstruous in appearance, dangerously intelligent, highly cunning, cruel, ambitious, technologically advanced. They shared the Imperium's ambition of galactic conquest and were just as determined.

The Rangdan Wars, as they are also known, consisted of three separate campaigns: The conquest of Advex-Mors, the Second Rangdan War, and the Third Rangdan war (also known confusingly as the Rangdan Xenocide).

the First Campaign occurred in 839, M30 and focused on the assault and destruction of Advex-Mors. This marked the first encounter between the Imperium and Rangda Empire, and it more or less incited the extreme response that followed. The system was heavily defended, including protection from an armada of Rangdan ships and an orbital war-moon. The latter was able to hold off the combined firepower of three Gloriana-Class Capital Ships. In fact, it was so well protected that some mistook it for the xeno homeworld. In reality, it was only a minor garrison at the edge of their domain. The fighting was fierce but nothing compared to slaughter that was to come.

The Second campaign kicked off in 862, M30 when the Rangdan struck back, plowing into Imperial space with thousands of vessels and more than a dozen war-moons. They attacked from the galactic east and north, overrunning entire worlds and putting the Imperium onto the back foot with shocking speed. Fleet after fleet was lost with all hands, entire Titan Legions were obliterated, and dozens of planets were destroyed as the Cerabvores continued their relentless assault.

Eventually, forces from the Vth (White Scars) and XIXth (Raven Guard) legions managed to delay the attack long enough for the Imperials to rally and make a stand at the Forge World of Xana. The siege would be broken after eight months and 3 thousand dead Astartes when the Dark Angels and Death Guard arrived to counter-attack. But this was only the next step in a war that would last two decades.

The Imperium wound up throwing no less than nine Legiones Astartes at the Cerabvores: the Dark Angels, Space Wolves, War Hounds, Death Guard, the II, Vth, XI, and XIXth Legions, and eventually the Alpha Legion. Even this wasn't enough, and the destruction continued unabated. The Space Marines committed to the conflict sustained heavy casualties. The Dark Angels especially got their shit kicked in; by the end of the Xenocides, they had lost their status as the largest Legion to Papa Smurf's blueberries. The Death Guard had to conduct emergency intakes of recruits just to keep their numbers up, and the II and XI Legions apparently ceased to exist during or shortly after the conflict, hinting that they may have been corrupted or otherwise compromised by the Rangdan and needed to be purged. The Lion received his baptism of fire in the Xenocides, as he had been rediscovered in the midst of the campaign and was almost immediately put in charge of the entire war effort. Despite his sheer Tactical Genius, the bloodshed continued, until the climactic battle at Taxal, when more than 300,000 Space Marines were deployed.

Eventually, things got so bad that the Emperor concluded he was going to have to do something incredibly dangerous: open up the Labyrinth of Night and unleash the motherfucking Void Dragon in an effort to break the Rangdan once and for all. Whatever happened, it totally worked and didn't cause a galactic calamity that we know of.

The third and final Rangdan War occurred between 887-890, M30. The numbers are unclear because at this point, the Imperium was more concerned with covering up the truth of how close everything had come to complete loss. A group of White Scars had managed to locate the Rangda home system after long searching. While broken, they were still a threat too grave to be allowed to endure. With a target now identified, the only thing that was left to be done was for the surviving Rangdan to be slowly, bitterly, painstakingly purged from the galaxy. What followed was a series of "bio-pogroms", a task which fell to the Space Wolves and the Dark Angels, as they were the two Legions the Emperor could most rely on to perform such an ugly and brutal job. This last phase of the conflict took a decade, as the two legions scoured the sector clean of the xenos menace. This earned the Space Wolves their nickname of the "Emperor's Executioners".

Outcome

After the end of the Xenocides, the Dark Angels and the Space Wolves had both been greatly reduced in number, meaning that the progress of the Crusade now rested on the Luna Wolves, Ultramarines, and the other Legions that hadn't been sucked into the meat grinder. The I and VI Legions also became objects of suspicion and fear among ordinary Imperial folk, thanks to the sheer ugliness of the bio-pogroms they'd undertaken (which of course makes so little sense it enters the negatives; people love it when space monsters are ruthlessly purged, but then GW has never demonstrated the slightest understanding of people). The Ultramarines officially became the largest legion, a status they would maintain throughout the remainder of the Crusade and into the Horus Heresy.

The conflict with the Rangdan also spurred the creation of newer and more terrifying weapons of war for the Imperium, most notably the dreaded Psi-Titans of the Ordo Sinister, which were directly inspired by the Rangdan's own superheavy and Titan analogues, the Macrobeests and Osseiovores.

Trivia

Interestingly, the Xenocides were also the first time "Alpharius" was heard of, even though the primarch of the XX Legion had yet to be recovered at that point. An Alpha Legionnaire using that name gained an audience with the Lion at some point, and offered to secretly take over the war so that the Dark Angels could withdraw and rebuild their numbers. The end goal, the Legionnaire explained, was to keep the Dark Angels from losing their status as the biggest legion and therefore improve the Lion's chances of someday becoming Warmaster of the Imperial armed forces, a position which both the Lion and "Alpharius" believed would be inevitable. The Lion turned him down because he was determined to finish what he'd started, which went well for his Legion. And of course he lived to regret this decision as, had he been Warmaster, the Horus Heresy would have been swiftly put down. At very least he could have brought the idea to the Emperor and leaned on Big E not wanting to lose his get-shit-done Legion full of Dark Age technology.

The mention of Slaugth Murder-Minds as part of the Rangdan forces also ties the Xenocides into the 41st Millennium via the xenos species of the same name mentioned in the Dark Heresy RPG. Not surprising, though, since the fluff for the Dark Heresy system and the first several Horus Heresy campaign books were both written by Alan Bligh, Emperor rest him.