|This page contains spoilers for:||For the Emperor (Novel)|
As of 931.M41, Gravalax was a minor agri-world on the border with the Tau Empire. Recent expansion by the Tau had left it with only a tenuous connection to the Imperium via a series of jumps through Imperial outposts. It was, in fact, deep within the Tau sphere of influence. The Tau had placed a trade mission on the world and over the course of a few decades, the human population had begun to support the ideals of the Greater Good, rather than the worship of the Emperor.[Needs Citation]
- The Valhallan 597th Ice Warriors Regiment
- The Valhallan 14th Armoured Regiment
- The Valhallan 12th Field Artillery
The Imperial presence was, however, merely a show of force. Gravalax was of no strategic value and would be difficult to defend if the Tau decided to take the world. Imperial policy was, therefore, to prevent a conflict with the Tau at all costs.[Needs Citation]
No sooner had the guard units arrived when local agitators, both pro- and anti-Imperial, began stirring up unrest. At a diplomatic reception to welcome the newly arrived Guard units, the Tau ambassador was murdered inside the Governor's mansion. The Tau were convinced, through the intervention of Commissar Ciaphas Cain, to restrain themselves from acts of revenge, but this did not stop the local Gravalax PDF from slipping into fraternal bloodshed.
A deal was eventually brokered with the Tau to allow the Imperial Guard into the capital city to suppress the fighting. The Imperial attack began with the shelling of the Xenoist faction stronghold. The area known as the Heights, and the Governor's mansion were the scenes of the heaviest fighting. Resistance by xenoist PDF and citizen mobs was futile as the battle-hardened veterans of the Imperial Guard moved in to prevent the burgeoning civil war.
A joint investigation by Inquisitor Amberley Vail and the Tau, eventually exposed Governor Grice as a Genestealer Patriarch, who had assassinated the Tau ambassador and whose genestealer infiltrators were attempting to provoke war between the Imperium and the Tau, to make the planet an easy target for an approaching Tyranid Hive Fleet.
During the final stages of the fighting, the Tau and the Imperial Guard actually allied to suppress the final rebellious elements, and Grice was killed by Inquisitor Vail. The genestealer presence on the world was carefully kept secret, and officially the Governor had been removed by the Inquisition for gross incompetence.
Ultimately the Tau withdrew from the world altogether, deeming the place too unstable to govern and therefore not worth the effort. However, the Imperium was wary, believing that the Tau would return at an opportunistic time, when the Imperium's military forces were concentrated elsewhere.