Event · M41–M42
Tyranid Invasion
The Tyranid Invasion denotes the recurring incursions of the Tyranids into the galaxy, first identified at Tyran in 745.M41. It was there, on the world previously known chiefly as home to the Zoats, that Imperial forces encountered advance elements of what would be catalogued as Hive Fleet Behemoth, a bio-mechanical armada driven by an instinct to consume worlds and convert their biomass into new Tyranid broods. The species took its name from that first engagement, and the Ultramar sector into which Behemoth pressed became the setting for the opening chapter of what the Imperium came to call the Tyrannic Wars. The course of the invasion was set by the hive fleet’s onward advance from Tyran toward Ultramar, culminating in the Battle of Macragge, where the Ultramarines under Marneus Calgar, reinforced by elements of other Chapters and Imperial Guard regiments, broke Behemoth’s main tendril at heavy cost. The victory did not end the threat: further hive fleets, among them Kraken and, generations later, Leviathan, entered Imperial space along different axes, splintering into unpredictable sub-fleets that struck Ultramar, Baal, and other systems in turn. Each incursion followed a broadly consistent pattern of vanguard organisms, genestealer infiltration, and swarm consumption, though accounts differ on the precise strength and course of individual splinter fleets, and the Imperium’s knowledge of the wider Tyranid threat remained, and remains, incomplete. In the present era the invasion is recorded as an unresolved and continuing danger rather than a closed campaign. The opening of the Great Rift has disrupted astropathic tracking of hive fleet movements, complicating the Imperium’s ability to anticipate where the Tyranids will strike next, even as successor Chapters, the Deathwatch, and allied forces continue to contest individual incursions across the Imperium Nihilus and Imperium Sanctus alike. The Tyranid Invasion thus stands as the durable, galaxy-spanning identity behind a succession of distinct hive fleet campaigns anchored to Tyran, Ultramar, and the many worlds consumed or defended since 745.M41.
See where Tyranid Invasion occurred on the galactic map in the 41st Millennium.