Tau establish base at Tanis

In order to protect the two remaining imperial systems from attack in the Hadron Expanse, general Percival was forced to allocate more troops away from the small expedition that had been sent to the Tanis system. Far into the Hadron Deeps, Tanis had been the last system the Hadron expedition had reached, and although the Space Wolves had set up a base, the Imperium were now down to a bare bones force that the Tau realised was vulnerable to a surprise attack.

Eventually, the Tau planned a full scale invasion of all the resource rich systems of the Hadron Expanse. However their war on Boltarean had ground to a halt, and they were still refitting after their conquests of Hussaria and Arawath. Oreen and Vanir were too heavily defended, but Tanis was not. Despite the distance from the Hadron Expansion sphere and the base at Echo Reach, the Tau decided to send their own force to the distant system, and fell upon an under-defended base on Tanis 3. The imperial guard stationed there were quickly overwhelmed by massive firepower, allowing the Tau to establish a forward base. Now the Tau had to decide whether to wait to see if their was an imperial response, or push ahead onto full colonisation of the system.