The Tranch War was a Mutant uprising against Imperial authority on the Hive World of Tranch in M41. It is notable for its brutality and ferocity, as well as being the birthplace of the Mutant warband known as the Pale Throng.
The uprising began when the Shroud Masters, the mysterious overlords of the Pale Throng, infiltrated the Hive World’s downtrodden and oppressed mutant population. The seeds of rebellion were spread, and the Shroud Masters trained and organized the vast mutant population of Tranch in total ignorance of the ruling Oligarchs of the planet. When the time was right, the mutant uprising began with a sudden all-out assault that saw entire Hive’s reduced to rubble and millions dead in the first few weeks. Imperial Guard forces were fast to react, drawing from forces all across the Sector to put down the mutant uprising.1
A brutal counter-insurgency followed, with numerous atrocities and horrors unleashed by both sides. However the decisive moment came when the Ordo Hereticus launched Operation Bellerophon against the Shroud Masters and their Rogue Psyker bodyguards. Using forbidden weaponry and unstable psykers of their own, the Inquisition operation succeeded in shattering the Shroud Council. Without the guidance of their rulers, the mutant insurgents began to fight for power amongst themselves and soon the entire Pale Throng shattered into smaller warbands which were able to be isolated and destroyed in piecemeal.
However though the bloody conflict had emerged in victory for the Imperium, it had been a Pyrrhic one. Most of Tranch lay in ruins and many of the Shroud Masters survived the conflict, leading Pale Throng warbands across the sector in a series of damaging raids against the Imperium. Meanwhile, the Inquisition decided to purge the Oligarchs of Tranch for their ineptitude, which had allowed the conflict to erupt in the first place.
Even to this day, there is much investigation regarding the ineptitude of several other Imperial forces during the early days of the assualt as well as suspicion of political motivation regarding certain questionable actions of the war, costing hundreds of lives and key victory points.