Two and a half centuries passed with neither sight nor sound of further Tyranid incursions. Some members of Earth's Adeptus Administratum began to question the necessity of maintaining so many armed forces in the galactic south-east to resist a non-existent Tyranid threat. They argued that the hive fleet had represented the sum total of the Tyranid race and that it had been destroyed at Macragge. When inhabited worlds along the south-eastern fringe began to suffer an epidemic of riots, terrorism, sabotage and, in some cases, outright rebellion the same Adeptus claimed the people had become dissatisfied with living in the midst of an armed camp and chosen to violently illustrate their displeasure.
The Inquisition suspected a plot and moved quickly to 'investigate" the dissenters for signs of treasonous thoughts or heretical influence. It was soon established that all of the dissenting Administratum officials either originated from the south-eastern fringes or had traveled there at some point in their career. No other unifying factors could be found, and many of the suspected traitors had never even met each other.
Inquisitors were dispatched from the Inquisition fortress at Talasa Prime to fully investigate the Ultima rebellions. Meanwhile, the Inquisition instigated a terrifying purge throughout the Imperium and particularly on Earth, incarcerating anyone in high office who had had contact with the Eastern Fringe. Tens of thousands were dragged away by the Arbites to languish in prison colonies while the investigation continued.
The Imperium's first concern was the rebellion on the industrial world of Ichar IV. The Ichar system is vital to the Imperium. Its gigantic factories and sprawling refineries form the lynch pin of one of the few densely populated sectors in the Ultima Segmentum. Thousands of ships carrying ore and myco-protein pass through Ichar's huge orbital docks each year.
The rebellion had been swift and bloody. Years before, a religious fundamentalist group called the Brotherhood had caught the hearts and minds of the impoverished city workers. Their preaching of the return of the Emperor had promised better times to come and a place in heaven at his side, the kind of spiritual comfort most sought after by those without power or privilege in life.
The Brotherhood's mercy missions and chapels had soon become a common sight in the poorest districts and their good works were legendary. The Ecclesiarchy had carefully monitored the Brotherhood for any taint of iconoclasm or heresy but had found nothing, if the reports were to be believed, but the most laudable of faith in the Emperor. Eventually permission was sought and granted for the Brotherhood to build a cathedral in Lomas, Ichar IV's largest city.
Shortly after the completion of the cathedral the trouble began. The Brotherhood refused to pay its tithes to the Planetary Governor and refused to allow its members to be inducted into the Planetary Defense Force. Brotherhood preachers began whipping the populace into a frenzy with predictions of the imminent return of the Emperor. Vigilante Brotherhood militias started to patrol in many areas, brutalizing far more "unbelievers" than non-existent criminals.
Matters came to a head when rioting broke out at a Brotherhood mass rally held before the great cathedral. Arbitrators moved in to break up the crowds with power mauls and suppression shields but were fired on from the cathedral itself. The Arbites returned fire, killing several Brotherhood militia and enraging the great mass of people. After beating off several charges by the mob the Arbitrators were forced to withdraw by the arrival of another, larger mob from the poor district.
Rioting spread throughout the city and the Arbites were unable to suppress it. When PDF troops were called from their barracks to assist the Arbitrators most of them rebelled and came out in favour of the Brotherhood. Vicious fighting broke out all over the city and, when it came to light that the Planetary Governor had been assassinated, the fighting spread to every city on Ichar IV. Within hours tanks daubed with Brotherhood symbols and flying crude revolutionary banners held most of the intersections and utilities in Lomas and the Imperial forces were being pushed back in other cities.
Dawn brought full news of the assassination of the planetary governor and most of his ministers. Some were killed by bombs, others by snipers, others were murdered with their households in horrific massacres which looked like the attacks of wild beasts or mob violence. Shortly afterwards the Brotherhood seized all broadcast stations and announced their new theocratic government.
Loyal forces still controlled much of the countryside outside the cities and the judges of the Adeptus Arbites still held their precinct fortress against the rebellious populace inside Lomas. Nonetheless, most of the world's cities had been captured in a full scale rebellion against the Emperor of Mankind. Inquisitor Agmar arrived on Ichar twenty seven days after the outbreak of rebellion, on the same day that the Arbites precinct fortress was finally overrun by Brotherhood forces. The judges were not to be so easily defeated, however. Most of their number escaped along a secret tunnel and captured the city's four main power generators.
To Inquisitor Agmar's eyes the situation on Ichar IV had the appearance of a well-orchestrated plot rather than the upsurge of popular opinion being depicted by the Brotherhood. Agmar requested the assistance of the Ultramarines Chapter of Space Marines to help the Imperial forces regain full control of Ichar IV. While they awaited the arrival of the Ultramarines the Imperial Guard regiments on Ichar bombarded the cities and held off ferocious counter-attacks made by Brotherhood militia battalions.
Repeated attempts to reach the trapped Arbites met with failure in the dense rubble surrounding the generator plant. Amidst piles of crumbled rockcrete and twisted girders Imperial Guard units were consistently driven back by the savage zeal of the Brotherhood troops in deadly close combats. The brave Arbites finally fell six days after Agmar�s arrival, though in their last act of loyalty to the Emperor they destroyed the power generators they had held so diligently. The lurid fires lit by their melta bombs burned for days afterwards, casting a black pall of smoke across Lomas like a chilling shroud.
The war had reached a stalemate and ground down into an extended city-fight. Casualties spiraled upwards daily in dozens of skirmishes and ambushes fought through ruined apartment blocks, burned-out factories and mangled refineries. Predatory snipers lurked, ready to kill the unwary. Every doorway could conceal a booby trap or a hidden enemy. Entire Imperial Guard patrols disappeared without trace in the maelstrom of combat.
At the other cities the story was the same. The Brotherhood had the Planetary Defense armories and the teeming populace to draw on for their soldiery, and they controlled the bulk of the planet's laser and missile silos. Siege and starvation would be necessary to drive them out.
Inquisitor Agmar led several small battle forces into Lomas to uncover more information about the Brotherhood. Piece by piece the picture of what had happened on Ichar IV became clear. He learned from prisoners about the ruling hierophants, heard their fanatical claims to be part of the magnificent "New Order" which would sweep through the galaxy. In a surprise raid he slew a Neophyte of the Brotherhood and saw what manner of creatures were leading this New Order. The divinations of the Imperial Tarot and Adeptus Telepathica psykers confirmed Inquisitor Agmar's worst fears. In utmost secrecy Inquisitor Agmar sent a report to the conclave of the Inquisition and awaited the arrival of the Space Marines.