The Tau Empire is a rapidly expanding alien stellar empire situated within the Imperium of Man's Ultima Segmentum, near the Eastern Fringes of the Milky Way Galaxy. The Tau Empire was founded by the Tau caste called the Ethereals, who lead the Tau Empire in the name of the philosophy they have named the Greater Good. Several intelligent alien races (the Kroot, Vespid, Nicassar, Demiurg and even some humans who have turned their backs on the Imperium known as the Gue'vesa) have allied themselves with the Tau. The Tau Empire borders the Imperium of Man, and lies within the reach of the Astronomican. It has suffered many raids from the Orks, and also seems to lie in the path of several Tyranid splinter fleets of Hive Fleet Kraken. Since their encounter with the Empire of the Combine Race, however, the Tau were forced into joining with the Alliance of Nations in search of support.
History
The Tau Empire in action.
The exact date of founding of the Tau Empire in the Imperial Calendar is unclear, however the the way in which the Tau were united as a species is a well-known tale. What is known is that only 6,000 standard years ago, in the 35th Millennium, an Adeptus Mechanicus Explorator fleet had discovered the Tau homeworld of T'au and determined that its population of sentient xenos were a primitive people at the Stone Age level of development who had only just mastered fire. They have developed very rapidly as a space-faring species. {C Earlier in their history, the Tau were a culture built upon warring tribes. During this time, the Tau's legends tell of the first appearance of the Ethereals at the city of Fio'taun. The fortress city of Fio'taun was under assault by the Tau warriors from the plains. Though negotiation had been attempted, the fierce plains warriors would settle for nothing less than the annhilliation of the city of Fio'taun. For five long Tau years the inhabitants held off the savage assaults with their thick walls and plentiful cannon. However, disease and starvation began to take their toll. As the tide of the siege turned, two mysterious Tau appeared. One made his way into the camp of the plains Tau, exuding a quiet authority that no Tau was able to resist. Soon, the leader of the plains warriors was persuaded to parley with the settled Tau of Fio'taun. Similarly, the other mysterious Tau made his way deep into the fortress. Within a few short hours, the gates stood wide open, and the Tau of both sides stood ready to talk. The Ethereals spoke of the importance of peace and understanding between all Tau. They described a Greater Good that each Tau must strive towards. The besiegers and the besieged quickly agreed with the Ethereals and a truce was reached. Across the world of T'au, Ethereals emerged, each with the same quiet authority and message of harmony and cooperation. With the Tau united, they were able to rapidly develop their civilization's technology, ultimately attaining faster-than-light spacefaring capabilities. The Tau Empire soon expanded its borders through a series of Expansion Phases. The Tau empire has gone through 3 phases of expansion as of the turn of the 42nd Millennium. These phases are marked by Tau military campaigns during which nearby worlds are colonized, conquered, or sometimes peacefully persuaded to join the Greater Good through diplomacy and a manifest demonstration of the benefits provided by advanced Tau technology. Therefore, apart from the star systems directly colonised by the Tau, which are called Septs, the Empire also includes the worlds and star systems belonging to the species of the Kroot, Vespid, and the Nicassar. It is currently unknown if the Demiurg are full members of the Empire, allies, or mere trading partners. The Tau Empire is composed of over twenty fully-developed Septs and around one hundered settled worlds, but the exact number and most of their names are unknown to the Imperium. A known splinter faction among the Tau are the Farsight Enclaves founded in the Damocles Gulf by the Tau Commander Farsight against the orders of the Ethereals. Also, more recently, some worlds and star systems of the Imperium of Man have been conquered by the forces of the Tau, while a handful have seceded from the Imperium and pledged their allegiance to the Tau Empire. At some point, the Tau sent an expeditionary force to the Imperial planet Malbrede where they came into conflict with the Ultramarines Space Marine Chapter in 936.M41. However, the planet proved to be a cursed Tomb World when the fighting of the Tau and the Ultramarines awakened the sleeping Necrons from their tomb beneath the surface. In an effort to combat this terrible threat to both races, the Tau and the Ultramarines combined their forces to defeat the Necrons. Once the conflict was over, the Tau were allowed to evacuvate their forces by the Ultramarines Chapter Master Marneus Calgar who proceeded to destroy Malbrede through the use of an Exterminatus order. In 966.M41, the Tau fought against the Adeptus Astartes of the Space Wolves Chapter during the War for Kvarium Alpha. On that water world, the Space Wolves' drop pods landed deep in the oceans where their occupants, their Power Armour altered by Space Wolf Techmarines to operate in undersea environments, made a move to engage their enemy. On the surface, the battle was fought between the two sides with an equally deadly conflict erupting in the depths of the sea between the Space Wolves and Tau Battlesuits. Thunderhawk gunships armed with torpedoes, prop-bombs and missiles were used to great effect against the Tau's Hammerhead tanks and Manta gunships. Ultimately, the Space Wolves proved to be the victor in the conflict, though hundreds of Tau and Space Wolf corpses floated to the surface. With their mission complete, the Space Wolves made the long trek back to land across the sea bed.
Government
When the Tau first started expanding to other star systems, they thought they were the only technologically advanced race in existence, and that it would be effortless to expand their reach throughout the rest of the galaxy. In 742.M41 (the 742nd year of the 41st millenium) they came into contact with the Imperium of Man, which launched the so-called "Damocles Crusade" to conquer the upstart Tau Empire. The war lasted for three years, between 742.M41 and 745.M41, before ending in stalemate - each side agreed to a truce due to the sudden appearance of the first Tyranid invasion of the galaxy, Hive Fleet Behemoth, which threatened them both. The Imperium's forces were rapidly withdrawn from the aborted Damocles Crusade to fight in the First Tyrannic War, and in such a fast panic that many Imperial Guard regiments were abandoned inside of the Tau Empire's territory, many of whom were absorbed into the ranks of the Tau military as auxiliaries. Each side learned new lessons from the Damocles Crusade: the Imperium of Man was forced to realize that the Tau were a new major race on the galactic scene, capable of standing up to the limited resources the Imperium was able to throw at them, due to most of its armies being spread thin across the galaxy fighting Chaos, Orks, and Tyranids. Meanwhile, the Tau had a rude awakening that the galaxy was not empty and theirs for the taking, but mostly controlled by the Imperium of Man, which even with its attentions divided between multiple alien threats controlled vast military resources. In the 250 years between the Damocles Crusade and the 13th Black Crusade (by the forces of Chaos), the Tau have been slowly but steadily expanding their sphere of influence, retrenching in the face of powerful alien races. As a civilized technological race which does not inherently embrace warfare, the Tau are one of the few races that the Imperium of Man might be considered to have "diplomatic relations" with on any level. This is not to say that the Imperium does not openly state that it would prefer to conquer the Tau Empire, simply that in comparison to many of the other threats besetting the Imperium -- the ruinous powers of Chaos, the sadistic Dark Eldar, the war-crazed Orks, the genocidal Necrons, and the all-consuming Tyranids - the utter destruction of all other life in the galaxy is not an inherent goal of the Tau. The Imperium of Man has been willing to enter into brief alliances with Eldar factions, particularly against the mutually hated forces of Chaos, though these do not last long. Imperial and Tau troops have never actually fought side-by-side as with the Eldar, and the Imperium could essentially be said to have been in a perpetual state of war with the Tau. However, in contrast to the more aggressive and all-consuming alien races in the galaxy, the Imperium of Man has been willing to enter into what could be considered open-ended truces and ceasefires with the Tau. As such, the Imperium still technically wishes to destroy the Tau at some point or another in the indeterminate future, but has given such concerns an incredibly low priority, to focus on the life-or-death struggle against more immediate threats from Chaos, the Tyranids, etc. Thus after many thousands of years, the Imperium of Man is slowly beginning to rediscover the concept of "international diplomacy", in which the Imperium, the Eldar, and the Tau would each prefer to conquer all of the others, but each also realizes that they do not have the resources for the full undertaking. Due to the Tau Empire's location in the Milky Way Galaxy's Eastern Fringe, combined with their lack of psykers, they have had relatively little contact with the forces of Chaos, which are concentrated around the Eye of Terror in the galaxy's north-west, or the Maelstrom at the center of the galaxy. The Imperium of Man has for the most part not prioritized military conflict with the Tau, which does occur but at a relatively low level. Contact with the Eldar is sporadic, and relations vary from one craftworld to the next. The biggest threats to the Tau Empire come from the Ork hordes, which control vast swathes of the Eastern Fringe, as well as the incursion of the Tyranid Hive Fleets, which tend to enter the galaxy through the Eastern Fringe (ultimately driving towards Terra). Thus the Tau's two biggest military threats are alien races which possess military doctrines diametrically opposed to those of the Tau. Both the Orks and Tyranids favor devastating close-quarters combat, while eschewing ranged combat (the Orks to a somewhat less degree than the Tyranids).