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Warhammer 40K Lore: The Expansion Of The T’au

6 Minute Read
Jan 12

The expansion of the T’au empire is a lesson in too rapid expansion and how increasing your “sphere” of influence is something fit only for humanity.

Come gather ’round Loremasters, as we examine the heretical hierarchy of the T’au and take a look at the ill-fated “expansion” of their empire as they encounter the galaxy’s various species and incorporate them into their culture instead of pronouncing exterminatus on everyone just for being different.

1st Sphere of Expansion

The First Sphere of Expansion, also known as the Great Expansion, was the initial expansion of the Tau Empire from their homeworld of T’au and was a period of unprecedented growth for the Empire. It lasted from 502.M37 to 956.M38.

The First Sphere of Expansion was launched from T’au and lasted roughly a millennium for the Tau. It saw seven additional fully settled Septs: Tau’n, D’yanoi, Bork’an, Dal’yth, Fal’shia, Vior’la, and Sa’cea. The Poctroon were the first race to join the Tau Empire during this period, though they were later wiped out by disease. Later, the Nicassar became the first race to join and endure. The Tau encountered the Orks for the first time during this period and tried to negotiate with them. But after the massacre of the delegates on the Kor’voss and Vaslan Prime, the Water Caste stopped these attempts and Tau fought with the greenskeens thereafter. The situation changed in favor of the Tau only after the Campaign of Cleansing. Also at this period a Thraxians race was assimilated. This was a terrific period of Tau growth that saw a massive population boom and unprecedented growth. The phase only came to an end because sparse Tau numbers could not keep up with their rapid advance and due to the sheer distance between systems that made crossing the span of the Empire impossible in a single lifetime. At the end of the Second Sphere of Expansion, the Tau encountered the Kroot, which eventually led to the Tau war effort to liberate them from the Orks in what culminated in the War in the Place of Union. For the next ten years, the Tau helped the Kroot drive the Orks from their worlds, eventually liberating their homeworld of Pech at the behest of the greatest Kroot leader Anghkor Prok.

During the intermission between the First and Second Spheres of Expansion, the Anthrazods and Brachyura were integrated into the Empire and helped prepare the Tau for the next war. However the key to allow for further Tau expansion came from the Sept of Fal’shia, where they finalized development of the ZFR Horizon Accelerator Engine. This finally allowed the Tau to attain near-light speed travel and launch the Second Sphere of Expansion.

2nd Sphere of Expansion

The Second Phase of Expansion (018.M39– ~700.M41) was the second major phase of expansion for the Tau Empire, launched with the advent of the ZFR Horizon Accelerator Engine, which finally allowed the Tau to achieve long-range space travel.

With a faster fleet and armies bolstered by new Kroot allies, the Ethereal Supreme, Aun’Wei, declared a new phase of expansion ready. The campaign was launched from each of the new Septs established during the First Sphere of Expansion. In 053.M39, the Vespid were successfully integrated into the empire while in 393.M39 N’dras was colonized.. In 576, the first Battlesuits, the T-series prototypes, were deployed by the Tau. It was during this time that Commander Puretide achieved legendary fame for the Tau, scoring victories that led to the establishment of Septs such as Tash’var and Elsy’eir. Puretide went on to thwart an Ork invasion that threatened Au’taal. The last breakthrough of the Second Sphere of Expansion was the successful crossing of the Damocles Gulf, something that led to first contact with the Imperium. The destructive wars with Humanity that followed were unlike anything the Tau had experienced and brought an end to the Second Sphere of Expansion. New Septs established during the campaign included Au’taal, N’dras, Ke’lshan, Elsy’eir, Tash’var, Vash’ya, and T’olku.

During the Second Sphere of Expansion, the Tau Empire encountered Hive Fleet Gorgon, the greatest threat the Tau had yet faced.

Also in this period the Vior’la Sept’s armies encountered a belt of lambent, crystal-rich asteroids and claimed them though only after the combat with some mechanical foes that fade from sight when slain.


3rd Sphere of Expansion

The Third Sphere of Expansion, launched in 997.M41, was the third campaign of expansion of the Tau Empire. Launched in the aftermath of the Great War of Confederation, the campaign was overseen by Commander Shadowsun.

With the Orks defeated in the Great War of Confederation, Ethereal Supreme Aun’va knew the time was ripe for a new phase of expansion. The great war against the Orks had pushed Tau civilization to a setting of total war, and they now could support campaigns larger then any before. The large and newly experienced caste of Fire Warriors would be bolstered with improved ship engines and stasis chambers, allowing for expeditions to be launched over much greater distances. Thus unlike past spheres of expansion which focused on specific star clusters, the Third Sphere encompassed a much larger region of space.

The expedition under Commander Shadowsun first crossed the Damocles Gulf and moved into Imperial space. Thanks to Water Caste agents, Gue’vesahumans were mobilized to conduct reconnaissance against Imperial forces. Some Imperial worlds simply surrendered at the first sight of the Tau, welcoming the Water Caste ambassadors and pledging for their cooperation. However most humans rejected Tau overtures due to their distrust of all xenos and Shadowsun and her armies were forced to sweep down in a series of precision strikes. The sparsely deployed imperial defenders proved unable to stem the Tau advance. Soon the northernmost sector of the Damocles Gulf was in Tau hands while the Galactic West was cleared of Hrud, Orks, and rebel humans. New Septs established during the Third Sphere of Expansion include Ksi’m’yen, Mu’gulath Bay, and Fi’rios.

Bowed by her initial success, Shadowsun rapidly led deeper advances. However the deeper she advanced, the greater the resistance she encountered. Seeking to avoid over-extension and the depletion of her forces, she instead broke up her forces into fleets, scattering them to a dozen different headings. Each began a devastating series of hit-and-run attacks which the Imperium proved unable to effectively counter. A pivotal battle was fought on the Hive World of Agrellan, where Shadowsun’s Warriors were accompanied by Aun’va himself, who sought to inspire the Empire’s troops. During the battle, the newly deployed XV104 Riptide Battlesuit was unleashed and laid waste to hordes of Imperial Guard heavy tanks and static defensive lines. Agrellan was renamed Mu’gulath Bay and soon the entire system fell with it. Shortly after the victory at Mu’gulath bay however Shadowsun became overconfident and suffered a stinging defeat at Voltoris.

Soon enough the Imperium would counterattack with elite Space Marine forces at the Zeist Sector, but this too was part of Shadowsun’s plan. As a diversion, this system was sacrificed for the Greater Good and forces there was instructed to stall the Space Marines for as long as possible. Meanwhile, Shadowsun struck deeper into more desirable neighboring systems. The worlds of the Imperium toppled one after another in the face of this precision assault. The Empire suffered a major setback when Mu’gulath Bay was destroyed during an Imperial attempt at reconquest.

Due to a multitude of vicious Imperial counterattacks in the Damocles Gulf region, the Third Sphere eventually ground to a halt. It was followed by the ill-fated Fourth Sphere and Fifth Sphere.


4th Sphere of Expansion

Launched in the aftermath of the Third Sphere of Expansion, which had ground to a halt due to Imperial counterattacks in the Damocles Gulf, the Fourth Sphere was an ill-fated expedition. Its forces were deployed at the time of the formation of the Great Rift and subsequently lost. When the Warp Storms caused by the formation of the Great Rift began to die down, the Tau would launch a Fifth Sphere.

It’s possible that elements of the Fourth Sphere lost in the Warp may have reappeared elsewhere, as evidenced in the Red Scar Campaign.

5th Sphere of Expansion

The Fifth Sphere of Expansion began on the heels on the ill-fated Fourth Sphere of Expansion, which was lost due to Warp Storms. When the Warp Storms began to dissipate and the Noctis Aeterna came to an end, the Fifth Sphere was launched.

~ Where will the Tau expand next – it is only a matter of time.

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