In the world of Warhammer 40,000, the Tau are a relatively young species among those contesting for power in the galaxy. Though young by the standards of the Empire, having attained basic technological proficiency within the last 6,000 years, the Tau have achieved a high level of technical sophistication- perhaps even higher than the level of the Empire itself. Unlike many of the Games Workshop Warhammer 40k races, the Tau are not simply a fantasy race put into space (like the Orks, Eldar, Dark Eldar, and Chaos forces). They are hominid in form (two arms, two legs, and a head), with bluish, hairless skin, flat faces with no discernable nose, and a wide mouth.

The Tau evolved on an arid, semi-desert world, where different groups of Tau were forced into different areas of the planet in order to specialize and survive. These specialized groups evolved into the four major castes that provide the basic organization of Tau society. Water caste Tau are merchants, beaurocrats, and negotiators. Fire caste Tau are fierce warriors. Earth caste Tau are craftsmen, farmers, and engineers. Air Tau are messangers, explorers, and staff that Tau offworld navy. A fifth cast, the Ethereal, serves as the leaders of Tau society, occupying a role somewhere between royalty and priesthood. The Ethereal seek to convince all Tau to serve the Greater Good of all Tau. The first members of the Ethereal caste settled a world-wide caste war that threatened to eliminate the Tau shortly after they achieved a modest level of technological achievement. Because of their mystique and the reverence in which they are held, the presence of an Etherial on the battlefield can inspire Tau warriors to great feats of bravery and daring. Conversely, the death of an Ethereal can send tremors through a Tau army that can cause chaos./p>

After the rise of the Ethereal class and the settlement of the war, Tau society began to advance at a rapid pace. Technological development outpaced the expected rate, and soon resulted in limited space flight and other advances. The Tau began to encounter nearby sentient races, most of whom were absorbed into the growing Tau empire. Most important among these were the Kroot, a barbaric race of warriors that have been regularly employed as mercenaries by the Tau to enhance their combat abilities. Contact with the Empire and other space-age races was limited. While a number of battles were fought with Orks, a large and persistant warpstorm blocked Imperial and other forces from entering Tau space for thousands of years. As a result of local space conditions and the warpstorm, the Tau did not develop long-range warp jump capabilities. Curiously, they also never developed psykers of any sort.

As the Tau developed technologically, contact with the Empire finally came (a few Imperial scouts had contacted the Tau prior to the development of the warpstorm, and a fleet dispatched to 'cleanse' the aliens, but the effort was stopped when the storm developed). Tau exploration vessels wandered into Imperial space, where they were engaged and destroyed. The Empire, recognizing the Tau from genetic samples taken by the early explorer missions, set out to destroy this new alien threat. Thus was born the Damocles crusade. A number of outlying Tau worlds were conquered or destroyed. But as the Empire pressed deeper into Tau space, they met with increased resistance, until they were forced to sue for peace. The Empire withdrew, only to be replaced by a threat to the Tau from Tyranid marauders. Such is life in the grim future ;).

Though they regularly take to the battlefield to defend their fledgling empire, the Tau are not a particularly warlike people (certainly not by the standards of Warhammer 40k!). Even the warriors of the Fire caste look upon hand-to-hand combat with disdain, seeing it as brutish and foolish. Not coincidently, Tau are ill-equipped for direct assault. They prefer to use their technology to their advantage, laying down a field of fire with pulse rifles and plasma weapons and employing networked drones and heavily armed and armored battlesuits. Even enraged Tau will usually let loose a withering hail of missle fire rather than dashing off into close combat. The Kroot, alies of the Tau, do most of their close fighting, while Tau Fire warriors, battlesuits, drones and artillery pound enemy positions from afar.