Event · M41–M42
Hive Fleet Behemoth
Hive Fleet Behemoth was the first tyranid splinter fleet encountered by the Imperium, its assault on Ultramar in 997–999.M41 culminating at Macragge. The fleet emerged from beyond the galaxy’s eastern rim and was first detected in 997.M41 when it fell upon the world of Tyran, consuming both Tyran Primaris and Tyran Secundus and giving the invading species its Imperial name. Advance elements of Ultramarines and Imperial Guard sent to Tyran reported a xenos threat unlike any catalogued before: a biological swarm that stripped worlds of organic matter and absorbed the dead into its own biomass. Behemoth then advanced deeper into Ultramar, its outriders striking Ichar IV and other systems along the fleet’s path, before its main tendril turned upon Macragge itself, homeworld of the Ultramarines Chapter. At Macragge the war reached its crisis. Chapter Master Marneus Calgar mustered the Ultramarines alongside Ultramar’s Planetary Defence Force and Imperial Guard reinforcements to hold the surface, a defence in which Calgar was gravely wounded and, by tradition, preserved through the intervention of Chief Librarian Tigurius. While ground forces contained the tyranid advance, Battlefleet Ultima moved to engage the hive fleet in the void above the planet, and it was this naval action that broke Behemoth’s cohesion and destroyed its main bulk in orbit. The First Tyrannic War thereby ended in Imperial victory, though at heavy cost to Ultramar’s worlds and defenders.
See where Hive Fleet Behemoth occurred on the galactic map in the 41st Millennium.