"This road will kill us all. Everything we are -- the brotherhood, the nobility -- all of it will be erased. History will never know what we once were, only what you would have us become. A horde of marauding berserkers, driven by nothing save the impulse to spill blood. Reavers and murderers, not warriors. How long do you think you can live as monsters before you force the Emperor to act? How long before the Eaters of Worlds join the others, the forgotten and the condemned?"
The Ghenna Massacre, known formally as the Second Compliance of Ghenna and the Ghenna Scouring, was an infamous campaign conducted during the Great Crusade by the World Eaters Legion against the world of Ghenna, where the entire planet's population was butchered in a single night of monumental bloodshed.
But the Primarch Angron paid little heed to the Emperor's dictates and ordered the work of the XIIth Legion's Techmarines and Apothecaries to continue with the mass production and implantation of the deadly cortical implants known as the Butcher's Nails in all of his gene-sons.
This infamous campaign would herald the inevitable fall and eventual damnation of the World Eaters.
Ghenna was an isolated Human world that had endured many of the horrors of Old Night. Its society was fairly technically advanced, but unfortunately, its population was overcome with genetic diseases. By the time of the Great Crusade, there were less than a thousand Gehennans that remained, kept alive in life-pods.
When this world classified as "Ninety-Three Fifteen" by the expeditionary fleets of the crusade, was re-discovered by the Imperium, they initially accepted Imperial rule peacefully. But after several Terran years of Imperial occupation, all contact with the world was lost.
The World Eaters under their Primarch Angron were despatched to investigate, and negotiations quickly broke down with the Ghennans when it was discovered that they had modified their own forms and were using an apparent form of Abominable Intelligence.
Angron ordered a hasty invasion of the planet, and per the Primarch's tradition, the World Eaters demanded that the world be subjugated within 31 solar hours (a standard Nucerian day).
Failure to do so, the Primarch declared, would result in the draconian punishment known as decimation, in which 1 of every 10 World Eaters was executed.
The prospect of 1 of every 10 World Eaters being executed for their failure as well as inadequate orbital, armour and artillery support led to a hasty and poorly executed landing on the planet under the command of the veteran, Terran-born Centurion Mago of the 18th Company. Mago was desperate to avoid yet another series of deaths among his own Legion brothers.
Yet when the World Eaters forces reached Ghenna's surface they faced no resistance, for the entire planetary population actually consisted of billions of artificially intelligent "simulacrums" designed to appear Human. These simple, unarmed constructs used their sheer numbers to swarm the Astartes, killing Space Marine after Space Marine no matter how many simulacrums were destroyed. Despite Mago's best efforts, for a time it seemed the World Eaters would be overrun.
Though the World Eaters finally received adequate heavy armour and artillery support just as they forced a breach and broke their way inside the confines of the main Ghennan city, the World Eaters once again failed to meet their Primarch's allotted time-frame of 31 solar hours to subjugate the planet and were forced to withdraw to the flagship, the Conqueror.
But aboard the Conqueror, Angron ordered the next round of decimation for his Legion. Mago refused, which amused his Primarch, who instead ordered Mago to personally execute the first World Eater who would die. When Mago again refused, Angron fell into a burning rage that saw him begin to murder dozens of his own gene-sons.
Only the Librarians of the XII Legion, under the command of Lectio Primus Vorias were able to finally subdue Angron by psychically forcing him into unconsciousness, though it cost the lives of several. However, Angron would not wake from his slumber, and soon, a crisis erupted within the World Eaters over what actions should be taken.
During this time of instability, Apothecary Gahlan Surlak announced that he had created a stable method of implanting the Butcher's Nails within Astartes by reverse-engineering Ghennan technology. The World Eaters could now implant these archeotech devices into warriors throughout the Legion as Angron had demanded since assuming control of the XII Legion. Mago found himself absolutely horrified at the prospect of his Legion being overwhelmed by the uncontrollable rage produced by the Butcher's Nails, and began to plot with his fellow Terran veterans of the War Hounds to prevent such an outcome and halt Surlak's plans.
Mago subsequently made an appeal to Centurion Kharn, and pleaded with him to reverse the dark direction their Legion was taking. However, his call for change fell on deaf ears. This forced Mago to take more drastic measures, and he gathered other disenchanted World Eaters that were loyal to him aboard the frigate Hound's Tooth.
They plotted to destroy Apothecary Surlak's equipment before he could fully perfect the Butcher's Nails implants for mass production and implantation. However, this attempt failed, and shortly thereafter, Kharn became the first World Eaters Legionary to be successfully imbued with the Butcher's Nails. With this initial success, Surlak proceeded to quickly implant a further 1,000 World Eaters with the cortical implants.
At this time, Angron awoke from his slumber, and with the Primarch leading these newly enhanced Legionaries, the World Eaters immediately launched a counterattack against the upstart Ghennans. The World Eaters, enhanced by the rage brought by the Butcher's Nails, slaughtered all those they came across, despite the massive numbers of simulacrums arrayed against them.
Thanks to Surlak's efforts, through his reverse-engineering of Ghennan technology, he was able to localise and pinpoint the location of the command signal that was controlling the actions of the simulacrums. By tracing the signals, the World Eaters discovered the shrivelled remains of the last true living Ghennans where they lay in their life-pods. There were only a little over a thousand true Ghennans, with each mentally controlling thousands of simulacrums.
The Ghennans pleaded with the blood-maddened World Eaters to be spared, but Kharn replied disdainfully that the galaxy belonged to the Imperium and proceeded to massacre them all.
Meanwhile, Mago and his conspirators felt they had no options left to save their Legion. They plotted to subdue Angron, Kharn and the other World Eaters who had been imbued with the Butcher's Nails. They intended to bring them before the Emperor Himself for judgement.
After the massacre of the Ghennans was carried out, the World Eaters on the surface were confronted by Mago and his supporters. They pleaded with their Primarch and Kharn to halt the madness, but once again, their pleas were ignored, and soon, a battle broke out between both factions.
During the subsequent fighting Mago was confronted by, and bested, his former friend Kharn, and before he was beheaded, made a final declaration. The XII Legion would be damned by their actions and the dark path Angron was forcing them to walk.
The Centurion's final words would later prove to be prophetic. With the death of their commander, the remaining rebels halted in mid-battle and submitted themselves for Angron's judgement.
With the XII Legion once again unified, the World Eaters proceeded to scour the surface of Ghenna clean of life, leaving no structure intact and no Ghennan left alive in a single night of monumental bloodshed. It was said that the psychic death screams of the dying were audible to Imperial astropaths across half the sector.
In the aftermath of this massacre, calls for censure against the World Eaters resounded within the Terran Council. Soon after, the Primarch Leman Russ and his Space Wolves Legion were dispatched to Ghenna to confront Angron and his World Eaters and to halt the implantation of the deadly cortical implants.
- The Horus Heresy Book One: Betrayal (Forge World Series) by Alan Bligh, pg. 88
- Betrayer (Novel) by Aaron Dembski-Bowden, Ch. 10
- Angron: Slave of Nuceria (Novel) by Ian St. Martin, Chs. 3, 6-9, 22-24, 26-28