When the mining world of Taros defected to the burgeoning Tau Empire, the Imperium dispatched a vast punitive expedition to reclaim what was theirs by right of conquest. The Taros Campaign was intended as a swift demonstration of Imperial power, but it became instead a lesson in the folly of underestimating the xenos.
The Astra Militarum and the tech-priests of the Adeptus Mechanicus landed in force upon the scorching desert world, only to find the Tau waiting. The blue-skinned aliens fought with patience and cunning, trading ground for time, bleeding the Imperial columns with precision strikes from battlesuits and hovering gunships. The unforgiving sun and the endless logistical chains strangled the invasion as surely as any enemy gun.
As the campaign dragged on, casualties mounted and supplies dwindled, until the Imperial command was forced to acknowledge an unthinkable truth: Taros could not be retaken without a cost the Imperium was unwilling to pay. The expedition withdrew, leaving the world to the Tau. In the vast ledger of the Imperium's endless wars, Taros was but a single failed line, yet it proved that the Greater Good could bloody the God-Emperor's finest and endure.