Tau

"Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive." -C.S. Lewis

Tau (τ) is the 19th letter of the Greek alphabet, 300 in Greek numerals, and also the name for 2π. Some people wish to use τ as an alternative to π. May I point you here for another view: http://en.wikipedia.org/wiki/Albert_Eagle

However, this article is about the Tau (or "bluies", as the Valhallan 597th call them), a playable race in Warhammer 40,000. When first discovered by humanity, the Tau were a barbaric and primitive people. Their planet was then trapped in a warp storm for a few thousand years and they emerged from the other side as a unified species, led by the mysterious Ethereal caste and devoted to the concept of the "Greater Good". Their new empire is currently about the size of Ultramar and growing. Although a dystopian society in its own right, the Tau Empire is noted for being one of the LEAST awful places in all the galaxy of 40k. It's also not really an empire; the Tau government, the Ethereal caste, is essentially an edifice of meritocracy and nepotism—Tau leaders are appointed to their position by even higher ranking leaders and/or a council of their future peers; the highest ranking Tau, the Aun'O, is selected by his future underlings, much like the Catholic pope, but is still simply considered the weightiest voice of a group (like a prime minister), not an Emperor with absolute power. While Tau civilization has the behavioral tendencies of many empires throughout history (expansionism, military conquest of weaker states, forcible integration of the conquered peoples, etc.), it's government structure that makes your state an empire, not your foreign policies.

The Tau started as a classic case of successful design-based trolling on the part of Games Workshop. They were originally developed because GW felt that their setting needed an optimistic race and that their wallets needed more money, which they could get by selling shedloads of 40k to the robot-obsessed Japanese. The Tau, therefore, are the least grimdark faction in the game; they're the dudes willing to negotiate when they've beaten their enemies, while all the others are either too murderously psychotic in ways incomprehensible to anyone who does not share the same batshit insanity, religiously overzealous, arrogantly indifferent, simplemindedly violent, murderously enigmatic, more interested in eating you than anything, or all of the above to offer such courtesies.

This began to change in the 6th edition when the Tau began to take on an Orwellian flavor, with the Ethereals being totalitarian autocrats performing acts of ruthless indifference towards their subjects in the guise of being for the Greater Good. Recent fluff (from Dawn of War, supported by Deathwatch supplements describing Achillus Crusade) has them ~~arbitrarily sterilizing the rebelling humans on Kronus once they come under the rule of the Tau Empire~~ sterilizing a group of humans attempting to revolt and distract Tau forces in the middle of a planet-wide, 6-way free-for-all (to be fair though, had it been anyone else they were revolting against, including the Imperials, those humans would be dead, most likely the slow and painful way, or even suffer such a terrible fate as to wish for death). The Tau Codex leaves ambiguous the question of just how much of their success is due to various forms of indoctrination, caste-based conditioning, and subtle mind control. This has only been exacerbated by the recent Farsight Enclaves supplement, which makes the Ethereals come off as mustache-twirling, Saturday-morning-cartoon villains. It speaks volumes about the 40k setting that in spite of all this they're still the friendliest race in the galaxy.

"Naive Weeaboo Space Communists"

The Tau's naiveté might seem at odds with the GRIMDARK-ness of the setting (and to a degree, a lot of it is), but the thing is, Games Workshop specifically plays this straight FOR the grimdark and knows that the seeming futility of the Tau's optimism only further accentuates the general hellishness of the rest of the galaxy - and dear god do they play this up for maximum effect. In the 41st millennium, the Tau come across as more than a little naive to the other races; the Imperium sees any contact with aliens as heretical and will shoot them with bolter rounds as soon as look at them; the Orks just want to kick the shit out of things; and the Eldar see the Tau as young and powerful because of their technology but also as a race in its infancy, just staggering out of its borders for the first time and wandering into a pond full of s harks.

Putting it simply, there's an ongoing joke that the Tau are some of the most successful trolling performed in the history of mankind just by existing; a case of the company installing them just to mix things up whilst at the same time keeping them surprisingly on-level.

The combination of the above fluff, however, paired with their highly advanced technology, generally "Asian" feel (their Fire Caste's combat doctrine is often reminiscent of Sun Tzu's "Art of War" - but derived from two distinct Tau hunting methods), use of battlesuits (just like the Imperium), heavy firepower which rivals that of the Imperial Guard, and one of the most broken tactics in tabletop 40K until it was finally fixed an edition later has conspired to make them very much hated (and by that we mean a source of butthurt) by a reasonable-sized population of the 40K fan populace, and /tg/ has rightly dubbed the Tau Weeaboo (as much due to their Asian-ness as anything else) as a result (even when people can use the same logic to point to the Imperium's xenophobia, the fanatical worship of the God-Emperor, extensive use of Mecha and suicide attacks, use of suicide attacks as punishment for dishonour, and fondness for over-the-top dialogue in general and conclude that the Imperium of Man is the space equivalent of Holy Imperial Japan). As a dark twist on this inherent Asian-ness, a thread concerning lack of grimdark fan fluff on Tau led to the creation of Sept V'iet, the Viet Cong Tau.

And again in a case of much cultural confusion, the Tau are often considered communists (despite being a rigorous, hierarchical, near-eugenicist class society that would drive Marx into RAGE) due to their central philosophy of casting aside the self in favour of the Greater Good. If anything the Tau more resemble the class system of Plato's Republic crossed with the caste system of India and Star Trek's Federation (because they're the only ones in the entire galaxy who bother to try diplomacy with xenos rather than exterminate them). However, the portrayal of the Tau as the equivalent of the Federation might still be wrong, since the Tau, amongst their castes, adhere to a highly strict doctrine of eugenics; any form of breeding between different castes or species is the Tau equivalent of HERESY. As well, the Tau treat their non-Tau comrades as second-class citizens with no say in the Tau government. Ergo, the Tau, despite not being the exterminate-all-other-species kind of racist, are still an ethnocentric, aristocratic empire hiding beneath the same type of veneer as the Federation, not unlike Britain during their 'tenure' as the rulers of India. To be fair though, if GW does decide to up the grimderp it would be more than safe to assume they would go the way of Stalin and start flaunting fancy propaganda posters everywhere—not that the Imperium doesn't already fill that part and the drawfaggots haven't already done great work in this field. What is for sure though is that, whatever part of the one-dimensional spectrum of political agenda they are on, the Tau government is mainly oligarchical, with the vast majority of political power concentrated in the Ethereal caste. This is further driven home by the fact there is a Tau splinter faction led by one of their two best generals alive, Commander Farsight of the Farsight Enclaves, whose government is a non-caste (presumedly socialist/capitalist hybrid), meritocratic semi-democracy. The problem is, until people stop dragging him out of his self-imposed exile to fight Tyranids, Orks, and other Tau, he's a dictator the way Optimus Prime is sometimes depicted. Farsight's government is one most certainly NOT recognized by the Tau Empire, who have finally gotten around to dispatching a fleet to silence them. This, of course, is imminent plot stuff that will never happen because it's always the 41st millennium, which is a good thing, thank you GW.

However, the new codex has HEAVILY downplayed their naiveté, bringing back the original codex mention that the Ethereals have officially declared both the Orks and Tyranids "lost causes" (took them long enough) and that the Greater Good demands they be killed to the last. Furthermore, they seem to have declared the Eldar "lost causes" too, perhaps due to their first contact with the Dark Eldar. (Although since they're battle bros with the Craftworld Eldar, it's probably just the Dark Eldar.) When a Tau fleet found an Exodite world while chasing a Dark Eldar raid, they straight up murdered every S&M hippie-elf on the surface—they didn't even try the usual "talk before shoot" method. Then again, few people will argue those sick bastards don't deserve it.

To sum it up, the Tau Empire is just as grimdark, evil and unrelenting as the rest of 40k, but they carefully hide their true nature behind the shining facade of the Greater Good. Kind of the Brave New World to the Imperium's 1984.

Military Doctrine

The Tau disdain melee combat in favour of ranged combat, which renders them instantaneously less manly in the eyes of most of /tg/'s playerbase. The reasons behind this are complicated. Generally, Tau see hand to hand combat in warfare as an anachronism, which makes sense, considering their basic guns can rip apart tank side armour, and compared to almost all other major races Tau have less muscle strength and reaction speed, which makes them ineffective in melee even if they are trained. Even the last reason alone is enough to avoid close combat, seeing as Necrons use similar logic, despite their Warriors and Immortals being much stronger and tougher, and actually highly trained in close combat, but equally as slow. That said, Tau do practice martial arts, but only for ritual purposes - Fire Warrior trials and rites involve knives and swords, while Ethereals have a tradition of fighting non-lethal duels to settle disputes, using sharp bladed weapons no less, so they are often quite good with their fencing style, as Aun'Shi has shown to some unfortunate Orks.

Logistically, Tau military doctrine has been hit hard with the same stupidity nerf bat as every other fieldable army, but is the only faction for which this violates their own fluff; every other faction has some reason for their materiel to be as limited as they would be in a fantasy setting, but the Tau have widespread education, unlike Men and Orks; reasonable access to production facilities relative to their population, unlike Necrons and Eldar; and are capable of coherent research and development, unlike Tyranids and Daemons. For fluff reasons which have never been explained (the crunch reason is obvious), they have the same motif as every other army of equipment often being more valuable than the person wielding it, leading to most personnel being fielded with inferior equipment. The most obvious example of this is that they always, under whatever circumstance, field infantry in simple combat armour rather than some sort of battlesuit - its only advantage is having less bulk, as if the Tau have a reason not to build larger transports to cope with the shitloads of battlesuits they could deploy instead. This argument is analogous to saying that real-world militaries should only use armored vehicles and not have infantry.

The Tau's superior firepower is similar to that of the Imperial Guard, but their strategy is different in that they tend to rely less on mass warfare and more on sophisticated technical support (drones, stealth technology, railguns), with an emphasis on tactical precision, mobility, and the initiative of individual squads of units, much like how modern warfare is waged (apparently if the Imperial Guard learned from Tau tacticians and fought with modern tactics instead of zergrushing everything then they would have been the most powerful army in the galaxy, but no, that ain't GRIMDARK and AWESOME enough [unless you're Macharius]). Their military doctrine is not based on winning by attrition and/or throwing out quality tactics in favour of absorbing and dishing out heavy shocks in bloody epic clusterfucks like the Imperials, Orks and early World War II-era Soviet Russia. (Unless you count the later war "deep warfare", which is actually the combat doctrine the Tau ripped off. 40k really seems to like the Russians...) Rather, they use infiltration and their sophisticated battlesuits to bypass enemy strong points and launch deep into their rear, cutting supply lines and logistics, destroying headquarters and support units, leaving enemies cut off and functionally helpless. There are numerous examples of Tau literally starving and/or thirsting entire armies to death by cutting out their supply lines, while simultaneously harassing them with night raids, ambushes and air strikes to the point the survivors are leaderless, demoralized, out of ammo and fuel, and can barely stand due to exhaustion. The Taros campaign is a prime example of these tactics (and of the Imperium's ~~tactical~~ strategic stupidity ~~since that would mean they lost ALL of their supplies~~ nah, they just couldn't deliver them to the frontlines, since ALL supply lines were cut).

90% of Tau dakka comes in the form of pretty blue lights.

The Tau, again, boast some of the most powerful ranged weaponry on the tabletop game, and can crank out more concentrated firepower than any other faction with the lone exception of the Imperial Guard, and even then, the Tau's weapons hit quite a bit harder. They have pathetic hand-to-hand combat skills, however, and so the Tau bolster this by using several inducted races (the Kroot, Vespid, and even some humans cut off from the Imperium during the Damocles Crusade) to act as buffers against assault troops to allow Tau Fire Warrior teams and their heavy, long-ranged firepower to tear enemies apart. The most pivotal, and perhaps most infamous, part of the Tau army are their Battlesuits, which can mount multiple heavy weapon systems and provide excellent mobility to their pilots, all on a fairly durable unit. They also have an extremely powerful navy, though not quite as formidable as the Imperium's, if largely because of number differences. Tau air units are among the best in the game, with aircraft superior or equal to Imperial Guard equivalents, including a stealth fighter, multipurpose heavy fighter, a superheavy fighter with guns that can one-shot a Titan, and their own Titan-equivalent (which is a small starship). Unlike the Imperium, they usually deploy swarms upon swarms of flyers, with only Orks and Necrons able to rival them in numbers when things come to dogfights—kind of the way the Imperial fleets' atmospheric support craft were supposed to work if fleet officers weren't a bunch of assholes who do everything they can to provide as little air support as possible.

On defense, the Tau are a bit unusual: they leave only token garrisons at their colonies to protect them. These garrisons are intended for scouting rather than combat, avoiding engagement in order to observe and report on invaders using Pathfinders, scanning towers, and drones. Because the Tau have fairly powerful spacefleets and usually keep their forces within reasoned distance of potential hotspots, any potential threat can be quickly dealt with by organizing a hunter cadre to be sent to deal with the situation. For those of you who don't get it, it's Frederick the Great's "he who tries to protect everything protects nothing" strategy. This has, however, backfired on occasion, since it does mean that the Tau garrisons are very vulnerable in the initial stages of an attack.

A rare advantage the Tau have is their willingness to change military strategy. As examples, look at how they changed tactics in reaction to the Damocles Crusade by the Imperium of Man, and even built an entirely new space fleet to match humans in straight-on space fights, or their unusual but effective choice of switching to older weapons when dealing with Hive Fleet Gorgon.

Non-combat Fluff

The Tau were a new race/culture found by the Imperium of Man during their "slash and burn" exploration of their galactic neighborhood. The Tau were still pastoral, had just discovered flint tools and charcoal, and the Imperium had them scheduled for "routine cleansing" (which is Imperiumese for ruthless genocide) to make sure they never got off-world and developed into an entity capable of threatening humanity. Needless to say, that plan was promptly fucked up. By an unfortunate (or fortunate, depending on your feelings towards a species' right to not be mercilessly exterminated for no reason whatsoever) coincidence which almost certainly involved the dickery of Tzeentch or Cegorach or something, a warp storm occluded the Tau homeworld, so nobody could get in or out. Since the Tau were virtually invisible in the warp, the warp storm didn't have much of an effect on them as they were immune to the influences of Chaos. The sector was labeled "lost to Chaos," and cleansing was deferred indefinitely. Only the Adeptus Mechanicus still had records of this first contact when the storm died down 6,000 years later. The Damocles Crusade relocated the Tau, who were completely untouched by the warp storm and now using interstellar colony ships and pulse rifles. The extermination order still stood—it was just going to be much more difficult than the Imperium expected, seeing as the Tau, instead of throwing spears and rocks at their tanks and Space Marines, were now throwing ion charges, plasma blasts, and electromagnetically-accelerated hypervelocity projectiles at their tanks and Space Marines.

Tau history is pretty typical up through the iron-age: a knack for engineering, warfare between "urban" farmers and "barbarian" nomads, and unrestrained growth causing a series of plagues, leading to a dark age. Here's where things go sideways, though the Tau see it as the start of their endless Golden Age: the arrival of the Ethereals. Legend tells of a five-year siege at the castle of Fio'taun, with both sides starving and succumbing to disease, when two foreign Tau entered the battlefield. One went to the castle, the other to the barbarian tribes. Each of these Tau had a quiet grace and irresistible authority. In just a few hours, the castle was persuaded to open their gates, and the barbarians laid down their weapons, and both parties met to parley a truce. These strange Tau called themselves "Ethereals," and stressed the importance of peace and understanding between all Tau. They described a "Greater Good" that each Tau must strive towards. Soon after, soon enough to seem simultaneous, more of these strange new Tau emerged across the continent with their message of peace and co-operation for all Tau. Their quiet authority was always respected, and their message of harmony was universally embraced. Wait a minute, I've seen this historical pattern before....

Perhaps uniquely for the setting, Tau-human interactions bear the whiff of realpolitik. On the one hand, the Imperium wants to exterminate them eventually, but the upper management generally realizes that the Tau are going to be a giant drain of resources and manpower to get rid of, given the stiff resistance they put up in previous campaigns and their uniformly advanced technology. Furthermore, they serve as a useful buffer state against various threats on the Eastern Fringe, from Orks and Chaos raiders to Tyranid hive fleets to alien forces the Imperium hasn't had (recorded) contact with. Their existence deflects danger from Imperial space, and in a place and time when the Imperium is coming under attack from all sides, that's more important than dogma. The Imperium's policy in dealing with the Tau thus largely focuses on containing its expansion more than retaking its worlds.

Conversely, the Tau have realized just how massive an undertaking expanding through the entire universe would really be, and are taking it slow. They mostly absorb Imperial buffer worlds stripped of manpower and armament in the face of massive redeployments to face other threats, offering the Empire's protection in return for annexation and outright conquering the places that don't take the deal. The Tau have claimed that they are engaging in this sort of aggressive behavior because someone's going to gobble those settlements up sooner or later, and if they don't do it, then whoever does won't be nearly as nice about it. While baldly self-serving, that logic is...well, mostly correct, really.

There's no lost love between the Imperium and the Tau, but open full-scale war is probably unlikely in the near-future.

Castes

Tau society after the arrival of Ethereals was organized into castes; everyone with a place, and a place for everyone. Interbreeding between castes has been outlawed by the Ethereals presumably to preserve the biological differences between castes, and as part of this effort they have taken over the practice of sex entirely. Tau society has been manipulated so that Tau do not form romantic bonds of a long-lasting nature and do not even consider sex to be anything other than a state-mandated act meant only, like everything else, to serve society and the Greater Good. In essence, Tau are conditioned to never have sex until and unless their superiors say they are worth breeding. Their superiors pick their breeding partners (the Tau get NO input into this) and the couple basically spends a few days off from work screwing around before going their separate ways to never see each other again. If a Tau did somehow get over their social conditioning and thought of sex as something more than a mandated duty, they'd be punished for illegal activities/perversion. An Imperial genetor's report in the fourth edition Tau codex observes the presence of synthetic proteins in Tau internal organs and suggests them as evidence that their evolution has been accelerated, though he might have been confused by synthetic proteins that the Tau were given. /tg/ seems to be under the strong impression that they are mammals, as you can see in the picture further down the page, despite the complete implausibility of this theory.

Shas (Fire)

The Fire Caste consists of the various warriors of the Tau Empire. The miniatures of a Tau army in a Warhammer 40,000 game are almost exclusively Fire Caste. Other castes think Shas are overly-aggressive hotheads due to their tendency to solve all problems by applying more plasma (when Tau encountered other sentient species, Fire Caste representatives immediately voted to hunt down exterminate them, just like they hunted down dangerous local life forms on the other world they colonized), although from the perspective of humans or eldar, who know better how "aggressive hotheads" actually look like fire warriors are seen more like a cold-blooded killers, even when they are enraged by the death of their Ethereal, which just shows how calm and disciplined other castes are. They are taller than Earth Caste Tau, and physically stronger than the Air and Water Castes, though still shorter and weaker than a typical Human. They pretty much compensate for this by giving their basic Fire Warrior a pulse rifle, which is sort of like an automatic sniper-plasma gun, and employ heavily armed and sophisticated battlesuits for their elite infantry. Oh yeah, and Railguns. Regiment-sized Tau forces are called "Hunter Cadres".

Fio (Earth)

The Earth Caste are the laborers and engineers; they are the "civilians" of Tau society. Their appearance can vary widely, though other Tau would describe them as "plain." They all have a stoic outlook, with little ambition other than to excel in their career of choice and work for the Greater Good. Unlike the Imperial worker classes, whose quality of life generally starts at working 14-hour days seven days a week while living off of dried, recycled dung chips and goes downhill from there, the Earth caste is mostly concerned with technological planning and engineering. They have robots to do the grunt work. The Farsight Enclaves field some Earth Caste pilots for their battlesuits, demonstrating their more flexible caste systems and/or their desperation for manpower. Doing so makes them even worse in close-combat than Tau already are, but they make up for it with technical training and tweaks to the suits' software and mechanics, re-rolling missed shots and equipment failures.

Kor (Air)

The Air Caste are the intermediaries between Tau. In more primitive times they served as messengers and couriers, and sometimes scouts/explorers, gliding on membranous anatomical surfaces through T'au's atmosphere. When the Tau started exploring offworld, it was the Air Caste that took charge of the vessels traveling between the stars. Now the Air Caste are the Tau stellar navy/airforce/mailmen, piloting the Empire's various carriers, warships, and emissary cruisers. Air caste Tau tend to be tall and slender like runners or dancers, and this is frequently exaggerated by the years the Tau navy spends in low-gravity. They are much less likely to be eaten by daemons due to a faulty Geller Field than their Imperial equivalents, but only because their ships are much slower, using a "slingshot drive" to temporarily enter the Warp and bounce back into real space.

Por (Water)

The Water Caste are the emissaries to non-Tau. They are diplomats, merchants, civil servants. The most open-minded Tau can be found among the Water caste, with some even showing individual ambition (but still for the greater good of the Tau Empire). When a new culture is encountered, the Water caste are sent in first to negotiate. If talks break down, the Water caste are withdrawn from the area and it's time for the Fire Caste to then start negotiating with pulse weapon fire. Also, unlike their Imperial equivalents in bureaucracy, the Administratum, they are brisk, efficient, and very good at their jobs. No dumping valuable ammo on an uninhabited dust world because no one signed the paperwork not to...though, give them a few thousand years and a few million light-years, and see how that holds up.

Aun (Ethereal)

The Ethereal Caste are basically the philosopher-kings described by Plato in "The Republic". They are selfless and always focused on what is best for the Greater Good ("Tau'va") for all Tau and every Tau without exception. The Ethereals are inspirational to all Tau caste members, and merely being near one will inspire a Tau soldier, engineer, pilot, or diplomat to work harder. In the case of the Fire Caste, some Ethereals accompany hunter cadres in battle during important deployments so as to better lead/inspire the troops, which works because all Tau in the combat zone will fight to their bitter deaths. They also seem to have semi-magical powers (don't ask how they work, none of the Tau know themselves) that allow Tau around them to do special things, like running while shooting. The Adeptus Mechanicus theorizes that the respect the Ethereal Caste gets from all other Tau is caused by a pheromone. ALL GLORY TO THE HYPNOTAU......

Also, Xenology relates a story from a minor, insectoid race called the Q'Orl which alleges that the Eldar stole one of their queens. Given that these queens have a magic, yellow, diamond-shaped sack that produces mind-control pheromones…well, let's just say the characters in the story figure it out quickly enough. There is a theory that the Ethereals themselves are also affected by their own pheromones, which could explain why they're so selfless and uncorrupted despite their absolute power.

Alliances

This article or section involves Matthew Ward, Spiritual Liege, who is universally-reviled on /tg/. Because this article or section covers Ward's copious amounts of derp and rage, fans of the 40K series are advised that if they proceed onward, they will see fluff and crunch violation of a level rarely seen.

In 6th edition, Tau are notable for being one of two factions (the other being Imperial Guard) who can ally with anyone except for 'Nids. Yes, this includes both Chaos Space Marines and Chaos Daemons, although, according to the Farsight Enclaves supplement, ~~Farsight is one of the only Tau (maybe the only one period) who actually understands the existence of Chaos, so the average Tau would consider them to be just another kind of alien.~~ Farsight rebelled because the Ethereals understand the existence of Chaos on some level, but keep it suppressed from the general populace so they're not entirely screwed. It still isn't going to end well though.

This leads to a few...interesting alliances, to say the least.

First off, Tau can ally with Orks, even though fluff-wise they are viewed as enemies of the Greater Good to be purged wherever encountered. Smaller Ork warbands (mostly Blood Axes) frequently act as mercenaries, of course, so the Tau might use them in that capacity. Plus, there might be fluff changes coming up (most notably, it was rumored that the Gretchin Revolutionary Committee would return in the new Orks codex; they, of course, would get along quite well with the Tau).

They are also battle brothers with both the Space Marines and Eldar, which has caused a large amount of headscratching on /tg/. The Eldar make a modicum of sense; after all, the Eldar most likely had a hand in their synthetic evolution and the creation of the Ethereals, and the Eldar are well known for being expert manipulators. A Tau-Space Marine alliance, though, would be odd, to say the least, since Tau and Space Marines are always going at it in the fluff. Of course, a minor chapter could always find an alliance with the Tau, or even join the Greater Good, but that seems far-fetched at best. Old fluff from back in the 3rd edition codex tells a story of a Tau commander letting an Apothecary remove the aul glands from dead Marines, establishing that the Tau are honourable warriors in the minds of this particular chapter. Isn't too hard to guess that someone at GW felt the battle brothers thing was a bit of a head-desk move, so they tried to fix it.

The weirdest part, though, is that Tau aren't Battle Brothers with the Imperial Guard, despite (or maybe because of) the existence of Gue'vesa (Imperial Guard defectors).

7th edition corrected all of this for the Tau, making them only battle brothers with themselves and certain allies of convenience, like Necrons and the Eldar, while the rest are desperate allies or, in the case of daemons and 'Nids, allies of the apocalypse. This effectively "fixes" the issue from the point of view of a butthurt puritan while still allowing for those who bought Tau models to include them as allies in their games.

Tau Member Races

The Tau are the only faction that willingly accept other races into their ranks. Typically, the races are extended a hand from the Water Caste first, and if they still pose a problem or otherwise refuse to be reasoned with, the Fire Warriors are sent in. The species, when annexed or conquered, are usually allowed to keep their planet, but must answer to the authority of the local Ethereal and possibly the local Shas'o. Most of them are fluff and don't show up on the tabletop, but it would get a little ridiculous if you could purport to play a 'single' 40k race that included, like, twelve different races.

Demiurg - Squats reborn. They are a race of spacefaring miners specialising in ionic weaponry who serve the Tau with their engineering and mining abilities. They also serve as an example of something the Imperium will never do: save dead codex races. (Well, okay, they're sort of saved...)
Galgs - Frog/Toad People who are regularly hired as mercenaries. No other information available.
Gue'vesa - Humans who have not only defected to the Tau, but chosen to take up arms and fight alongside them to serve the Greater Good. Serve in-fluff as Auxiliaries, but not supported on the tabletop. (If the current trend goes on we may see Sisters join up with the Tau, which might be an improvement for the Sisters.)
Hrenian - Alien mercenaries employed for their skills as light infantry. No other information available.
Ji'atrix - A spacefaring race. No other information available. (Dammit, GW writefags.)
Kroot - Predatory gene-assimilating avian humanoids. They are the first alien race to be actively recruited by the Tau as mercenaries, and are so regularly hired that they have officially progressed to being considered Auxiliaries of the Tau forces.
Mal'kor - Insectoid aliens, also known as Vespids, who are native to a gas giant planet within the Tau Empire. Serve as Auxiliaries.
Morralian - Also known as "Deathsworn". No other information available.
Nicassar - A voidfaring race of psykers and the only psychically-gifted species in the Tau Empire. The Tau have carefully hidden them away from the Imperium due to their (actually justifiable) psyker-phobia.
Ranghon
Tarellian - These guys are basically Lizardmen IIIIN SPAAAAACE!!!!!! Not really part of the Empire, but rather mercenaries who will gladly fight humans and Tyranids on the cheap since the Imperium virus-bombed their home world and the Tyranids nommed their biggest colony.
Poctroon - The first sapient species to be found by the Tau, they were "accidentally" driven extinct by Tau smallpox, and their planet just by coincidence was a great place to set a Sept World.
Nagi - Brain worms that, due to their horrific appearance and inability to communicate, were attacked by the Fire Caste. They managed to sort it out, though, and now they work with the Ethereals as advisors (because having brain worms about as "advisors" isn't a bad idea or anything).

The usually genocidal actions of the other races, most notably the Imperium, also serve as a motivating factor for less-powerful races to join the Tau. While the Tau do seem a minor threat to the Imperium now, if the current policy continues, there will be more and more races joining up with the them if for no other reason than avoiding extermination. Of course, the Tau are just coming to realize how vast and powerful the Imperium really is, and while a lot of their member races really are the victims of crazy, evil, fascist extermination protocols, there's always the chance that someone responsible for a "Hell World" or "Nightmare World" might join up, and the damage might be done before they realize their mistake...

In a Nutshell

The Stated Reason Why People Hate Tau

Weeaboo space communists—not grimdark enough.

The Real Reason Why People Hate Tau

Until the edition update, this would, most assuredly, be Fish of Fury. Fuck, even most Tau players felt this was bullshit.

Post-edition update, it was that certain undesirables felt that they were trying to take the mantle of the 40K universe's "rightful" Imperial protagonists. And because they are not choppy enough.

And then 6th Edition codex came, and Tau became one of the shootiest armies in the shootiest edition ever, not to mention their ability to bitchslap cheesmongers, having straight counters against any of the Wardex bullshit.

A Real Reason Why People Like Tau

The one race that isn't being a wall of dicks. If the Tau are trolling done by Games Workshop, then the target of said trolling was any fatbeard that needs a constant supply of grimdark to stay alive.

The Real Reason Why People Play Tau

Arguably have the most powerful guns in the game. Often twin-linked. Often on cool-looking robot battlesuits. Also markerlights. Also RAPETIDE. Tau players may also have a tendency towards sadism.

Helping Necrons? Or are they Necrontyr descendants?

An often overlooked issue is that Tau have ~~no warp~~ almost no warp signatures, just like Necrons, hate Warpspawns and Warp in general (despite the fact that in 6E they can work with them...I just...I don't...WAAAARD!!!), just like Necrons, have the exact same skull shape, stature and short lives, and the overwhelming need for Technology and beam weapons, JUST LIKE NECRONS. GW may have planned a race that simply prepares a pacified, multiracial galaxy for Necrons to feast upon, supported by Ethereals that have a C'tan phase blade. Then there is a reference of "dark seed in east" by the Deceiver, so the tricky C'tan might give Tzeentch the finger in the JUST AS PLANNED competition. Or maybe GW just has so little creativity that they simply made a new civ conforming to an Old One's standards without knowing it. Given that recent murmurs have suggested that something absolutely massive is in the works at GW, anything could be possible, though past experience has led us to believe that it will simply be a Tau wearing a silly hat. However, seeing as GW is as likely to advance the plot that far as I am to shove both my legs up my ass up to the knee, it doesn't much matter.

TL;DR

High-tech alien race who are the least grimdark of factions. Can't melee for shit but can blow you back to the stone age with ranged weaponry if you have the misfortune of being downrange. You will either love them or hate them because of all this, and many neckbeards do feel the butthurt. Or, as the saying goes: "You can't spell TAUNT without TAU."

Warhammer Fantasy

Unlike most other factions in 40k, Tau have no clear antecedent from Warhammer Fantasy. Some think the anime influences and rapid industrialization/militarization point towards Nippon; others feel the caste system might be related to the Kingdom of Ind. However, neither faction has ever been explored in great detail (or any detail at all), so it's impossible to say whether Tau are similar to those factions; instead, we must compare to the real-world equivalents of the Old World nations. Slightly more controversially, there are elements of Cathay (which is the Anglicized word for China back in the British Empire heyday, so yes) in the Tau. Cathay has been described as being technologically advanced (at least on par with the Empire), including terra-cotta automaton warriors (which the Chinese definitely used to make to pay homage to the First Chinese Emperor's over inflated ego, more than a millennia ago), although such comparison is stated by some to have already been implemented in the characterization of the Eldar and thus, is considered as seriously stretching up a notch.

More recently, some have connected the Tau and their subject races to other factions in Fantasy. The rapid evolution of the Kroot and their overall savagery is (somewhat) similar to the Gors of the Beastmen (although the Beastmen are in the 40k universe themselves). The Empire also shares the xenos-friendly viewpoint of the Tau, although they're not expansionistic, and decidedly less concerned with a unified government structure so long as everyone pays their taxes, for better or for worse.

Notable Tau

External Link

A Typical Tau-Human conversation.

Should one of your Tau actually kill anything tougher than a guardsman in melee, you are allowed to end the game in victory as long as you play this clip. ~~Apparently someone did it....~~ BLAM! HERESY!

Gallery

This article contains PROMOTIONS! Don't say we didn't warn you.

A Tau Fire Warrior, the basic infantry unit.
And a smaller one.
Gue'la.
It's a well-known fact that the Tau Empire has some of the best shopping in the entire galaxy.
Stealth suits are :3
Indeed, many humans have already embraced the Greater Good. (The individual with the primitive flashlight has been sent to re-education. Happiness is mandatory, Citizen.)
Sweet weeaboo heresy.
Some recruitment methodologies work better than others.
Ohhh GW.
Few rarely seen Tau chicks. Maybe because Sisters are hotter.
Fire Warriors are :3 too
The sad truth of 6th edition.
This Char Custom Battlesuit-clad Tau demonstrates his mastery of Weeaboo Fightan Magic. Also DYNAMIC ENTRY!
The Imperial Infantryman's Uplifting Primer's entry on Tau players.
Surrender... never shall the Tau.
Tau are vicious melee fighters, no less able than Space Marines!
Yeah, we all know the truth about their "greater good".
MARKERLIGHTS!
In spite of being filthy heretical xeno scum, the Tau can really break it down.
Here we see Tau propaganda meant to entice men with their terrible, blasphemous, and supple soft skin, smooth curves, perky brea...er...ah...heretical alien bodies.
An attractive human female defector who for some reason has been equipped with a highly modified commander's battlesuit, perhaps as a devious ploy to compel desertion by the less loyal.
DAT ASS
A Fire Warrior appreciating DAT ASS.
In hindsight, attempting negotiations with Orks was probably a bad idea.
In /tg/, tau are the evil guys.
Typical Tau player, engaging in typical Tau behavior. (Pretty badass cosplay, even got the hoof right)
What's that? We're not grimdark enough for you, Neckbeard?
A Greater Good we can all believe in.
Fun fact: if you have enough money to buy this, you have too much money.
S-shut up you filthy sluts! Among my people it is considered quite a handsome dick!
Propaganda. Sound familiar?