The battle began when Tau diplomats managed to establish an uneasy peace upon the planet of Ur-Clemait, a world that has long been ravaged by civil war. Thoughmost of the population seems content with the Tau’s enforced ceasefire, the elders and priests of the old faith are distraught, insisting that the ‘blood tithe’ must continue to be met. The puzzled Tau continue their assimilation, but before the year is out, the Word Bearers arrive to enforce the tithe. They attack Ur-Clemait in force, cutting down xenos and human alike. The Tau Fire Caste meet the invasion head-on, and the world is plunged into an ongoing war far worse than the previous.