The Damocles Gulf Crusade, also called the Damocles Crusade, was the first military conflict fought between the Imperium of Man and the rapidly expanding Tau Empire in the Lithesh Sector of the galaxy's Eastern Fringes between 742 and 745.M41. The conflict essentially ended in a stalemate in late 745.M41, as the Imperium was forced to conclude its military offensive early to deal with the encroaching Tyranid threat while the Tau sought to begin diplomatic negotiations with the Imperium to show humanity the benefits to be had by accepting the Greater Good.

Members of the Tau Water Caste had established trade agreements with Imperial worlds on the frontier of the Tau Empire, near the Damocles Gulf region of the Ultima Segmentum in the galactic east, and exchanges of goods and technology were common. Alarmed by the threat of alien contamination, the Administratum readied a suitable response and almost a century later, the Damocles Crusade smashed into Tau space, destroying several outlying settlements and pushing deep into the Tau Empire.

When the Imperial fleet reached the Tau Sept world of Dal'yth Prime, however, the Crusade ground to a bloody stalemate as the formidable numbers and high technology of the Tau and their Kroot allies thwarted every attempt to capture the world or its star system. Many months of terrible fighting ensued with nothing gained on either side. By late 745.M41 the Crusade's commanders eventually agreed to requests from the Tau Water Caste for peace talks. The negotiations were successful and the Imperial fleet withdrew from Tau space unmolested, primarily due to the impending approach of the Tyranid Hive Fleet Behemoth

The Tau and Humanity

Map damocles gulf

Departmento Cartographicae Map of the Damocles Gulf


The worlds of the Damocles Gulf


A map of the Damocles Gulf before the start of the Tau Empire's Third Sphere Expansion

Exactly when the Tau Empire and the Imperium of Man first made contact with one another is unknown, for each was slow to recognise the nature of the other. For the Tau's part, it was fringe, dissident or overtly Renegade elements of humanity that they first encountered, in the form of Free Captains and pirates across the coreward borders of the region called the Damocles Gulf in the Eastern Fringe to the galactic east of Terra.

The initial contacts ranged from friendly negotiations and trade to outright hostility. It was some time before the Tau Water Caste diplomats understood the fact that the humans they had encountered were merely the forgotten outcasts of an incomprehensibly vast interstellar empire that stretched across the entirety of the Milky Way Galaxy. This empire was so vast that any overt aggression on the Tau's part might lead to the outright destruction of their nascent empire and the extinction of their species. Though many of the more passionate leaders of the Tau Fire Caste called for a war of conquest against the Imperium, the Ethereals issued their instructions for the integration of the Imperium of Man into the Tau Empire.

The Water Caste were to align themselves with nearby dissident human factions and over the course of several decades of patient negotiations insinuate themselves into the courts of several dozen Imperial Commanders (Planetary Governors). The influence of the Tau thus spread further and more rapidly into the Imperium than any amount of military conquest could have taken it, until a swathe of human worlds were trading with the Tau Empire in preference to the Imperium's own merchant trade cartels and Rogue Traders. Alien goods and technology flowed through the markets of these border worlds in blatant contradiction of the laws of the Imperium. The second phase of the Ethereals' instructions were thus ready to be initiated.

Upon a score of worlds, Water Caste envoys whispered long-rehearsed words into willing ears. The seeds of rebellion had long been cultivated by the Tau and now bore traitorous fruit as each Imperial Governor declared himself free of the shackles of the Imperium's rule. In the ensuing power vacuum, the Tau Empire expanded, claiming for themselves those human worlds that came to be known as the Farsight Enclaves.

The Imperium's response was unusually swift but characteristically brutal. War was declared and the Damocles Gulf Crusade was launched by the Ultima Segmentum Command, involving units of the Imperial Guard, the Imperial Navy and the several Chapters of Space Marines. Within a short period of time, the Tau's influence was pushed back across the Damocles Gulf, but only at great cost to the human armies. In time, the momentum of the Imperium' armies was spent and more pressing concerns, such as the first Tyranid invasion of the galaxy, called for their more immediate deployment.

An uneasy peace ultimately descended across the war-torn border sectors of the Imperium and the Tau Empire. The Imperium had demonstrated but the smallest fraction of its size and power, yet the Tau had gained invaluable insight into its methods, strategies and tactics. More importantly, the Tau had learned that those humans who were disenfranchised or rejected by the Imperium could be manipulated. Surely, the Tau Ethereals reasoned, no matter its size, no power so given to devouring its own people could ultimately stand before the manifest destiny of the Tau to expand the Greater Good across the galaxy.

Prelude to Conflict

The Second Sphere Expansion of the Tau Empire culminated in the Tau crossing the Damocles Gulf and making contact with the frontier worlds of the Imperium in the Timbra Sub-sector of the Lithesh Sector. These worlds were known by the Administratum to harbour rebellious tendencies and when they did flare up in rebellion following their contact with emissaries of the Tau Empire the Inquisition knew exactly who to blame. The Tau were quickly condemned as a potentially dangerous xeno species and the Imperium's Ultima Segmentum Command launched a Crusade to expel them from the region.

The Damocles Crusade was a military action typical of the Eastern Fringe of the galaxy before the arrival of the Tyranid Hive Fleets. Wherever possible, when challenges to the authority of the Imperium of Man were discovered, war followed to exterminate the threat. In 742.M41 another such Crusade was unleashed in the Lithesh Sector. A string of Imperial sub-sectors stretching out between the Damocles Gulf and the Perdus Rift Anomaly had suffered extensive disruption due to Eldar pirate raids and Warp Storm activity. As the Imperium sought to restore its grip on the region, it was discovered that a previously unknown intelligent alien race called the Tau was allying themselves with rebel Imperial factions. The peril of these local alliances was evident in the number of alien trade goods and artefacts appearing in the nearby Imperial star systems.

Inquisitorial investigation of the dissident worlds by the Ordo Hereticus revealed evidence of Tau activity in adjoining sectors. The conclusion was that they represented a major threat and Cardinal Esau Gurney of the world of Brimlock called for an Imperial Crusade to be dispatched to purge the aliens. The Crusade was based around a dozen capital starships of the Imperial Navy, 5 provisional companies of Space Marines made up of contingents supplied by almost a dozen different Chapters and 19 Regiments of Imperial Guard, seven of them from Brimlock. The first move was towards the Timbra Sub-sector where human colonists had long coexisted with the aliens. The Crusade first reasserted Imperial rule in the rebellious Garrus and Kleist colonies. Individuals implicated in dealing with the Tau were seized and punished at a special assize held before the furious Crusaders. The Imperial colonies secured, the Crusade forces moved on and engaged the Tau for the first time on their own territory in the uninhabited Hydass System.

First Contact: The Battle of Hydass

Seven Tau warships of approximately Cruiser displacement were detected on the edge of the Hydass System. The Crusade fleet attacked immediately, but found the Tau starships to be capable of launching powerful torpedo salvos at long range, breaking up the Imperial formation. Bomber waves were launched but these were countered by Tau Escorts launched from their capital ships. A Space Marine Strike Cruiser supported by a squadron of Sword-class Frigates made the decisive attack. Getting inside the Tau formation, they inflicted heavy damage and discovered that Tau starships lacked broadside firepower. The Tau launched more Escorts as a screen while they disengaged. One Tau starship was unable to withdraw and exploded while the crew was in the process of abandoning ship. The Imperial Crusade fleet then moved deeper into Tau Empire territory.

Ground War: The Battle of Sy'l'kell

The Sy'l'kell System contained an apparently fertile Agri-world with a population estimated at 7 million Tau. It was defended by an orbital space station, a number of system ships and the remnants of the Tau fleet encountered at Hydass. The Crusade's council of war appointed Captain Rumann of the Iron Hands Space Marines Chapter to take overall command of the planetary assault. The Imperial fleet closed quickly, pounding the orbital station as they approached. Its armaments were not as extensive as had been believed at first and the Iron Hands Space Marines in the fleet boarded it. The Tau fleet disengaged almost immediately and was not seriously damaged. It was conjectured by the Imperials that the Tau were evacuating their key personnel from the planet rather than bothering to defend it. The Iron Hands quickly overwhelmed the orbital station's defenders and dutifully cleansed it of xenos taint with flame. It was to serve as the Imperial forward base for the ground campaign on the world.

Astartes from the Scythes of the Emperor Chapter established a landing zone and the 17th Brimlock Dragoons Regiment of the Imperial Guard were landed to provide heavy support. The Tau response was swift and consisted of an extremely well-armed mechanised infantry formation with armoured support. The Tau grav-tank called the Hammerhead appeared to be a close match for the Imperial Guard's Leman Russ main battle tank and the Tau proved very adept at supporting their armour with Fire Warrior and Battlesuited infantry. The Dragoons suffered heavy losses when enemy infantry wearing Battlesuits ambushed them in rolling ground. Only swift intervention by the Imperial Guard's 4th Storm Trooper Company and the Scythes of the Emperor Space Marines prevented an out-and-out massacre. While the Crusade pushed ever nearer Sy'l'kell's main population centers, the Tau evacuated the most qualified Earth Caste workers and dismantled any of their advanced technology. When the 9th Brimlock Fusiliers were landed, the Tau resistance crumbled and all Imperial objectives were quickly attained. The planet was duly cleansed of xenos taint and claimed for the Imperium.

The Purging of Viss'el

While logistical arrangements were made to cross the Damocles Gulf to the Imperial designated Sub-sector of Kendral, an expeditionary force was sent from the main Crusade fleet to deal with the Tau presence in the nearby Viss'el System to remove a potential threat in the Crusade's rear. Early Imperial reconnaissance had revealed that Viss'el VI was an Ice World on which the Tau had established fishery colonies. As no great strategic benefit was to be had from conquering the world, it was subjected to orbital bombardment, melting the ice around the Tau colonies and destroying them in flash floods.

The Dal'yth Campaign

The Battle of Pra'yen

After a 5-month-long journey across the Damocles Gulf, the Imperial Crusade fleet arrived in the Dal'yth System within the Kendral Sub-sector. The outermost planet in the system, Pra'yen, was protected by a Tau orbital space station and was clearly intended to provide the first line of a layered system defence. The fleet's approach proved too casual, as the Imperials assumed the station to be no more dangerous than the Tau station already encountered in the Hydass System. It proved to be much more formidable, mounting an array of heavy Railguns whose first volley crippled the Honour of Damlass. The Imperial fleet broke formation just as 11 Tau starships emerged from behind the bulk of Pra'yen. The Imperial fleet escorts attacked the orbital station while the main battlefleet swung towards the Tau vessels. The Tau fleet concentrated its torpedo salvos against the Regent Lakshimbai, a Dauntless-class Light Cruiser, which resisted heroically until a lucky Tau shot caused a massive bulkhead collapse which then triggered a plasma drive overload, destroying the vessel with all hands aboard. Arriving piecemeal, the Imperial starships gradually won the advantage, although on this occasion the Tau continued to fight despite taking a terrible pounding.

The Imperial Escorts suffered heavy losses fighting the Tau orbital station. As soon as they were closely engaged, though, the last piece of the Tau trap was sprung. Appearing seemingly out of nowhere after suddenly powering up their main systems, a Kroot warsphere headed directly for the Imperial troop transports. The transport flotilla had no choice but to scatter. The huge Kroot hulk was slow and its weapons were short-ranged, but its sheer size seemed certain to eradicate the Crusade's ground troops. Salvation came in the form of Admiral Jallaque's flagship, the Blade of Woe, a Retribution-class Battleship. Leaving the rest of the Imperial fleet to finish off the Tau warships, the admiral had turned his vessel about, planning to help the Escorts when the Kroot warsphere arrived. Accelerating to maximum power, the great starship overtook the lumbering warsphere and turned across its path. From the first exchange of weapons it was clear that the Blade of Woe carried the greater weight of fire and its lance salvos quickly ripped the warsphere to metallic shreds. Yet the Crusade fleet had won only a pyrrhic victory. Although the warsphere, Tau fleet and the orbital station were destroyed, it was at the cost of 4 Imperial capital ships and 14 Escorts. The Tau ambush had come very close to succeeding and brought a new respect for the Tau as combatants to the Imperial fleet.

The Battle of Dal'yth Prime

Although some members of the Crusade's command council now advocated turning back, the lure of an assault against a major Tau world proved too tempting. Dal'yth Prime was protected by three Tau orbital stations and, following the recent combat, these were approached much more cautiously. None proved to be as heavily defended as Pra'yen, however, and were destroyed at leisure by the Imperial fleet. Expecting a new Tau fleet at any time, the Imperial ground assault quickly commenced. The eastern seaboard of Dal'yth's largest continent was selected as the target for the landing. Protected to the north by mountains and to the east by the sea, a short advance southwest put the Imperial invasion force before the first of a number of major Tau cities along the coast.

The drop was contested by large numbers of Tau aircraft but eventually proved successful. The full force of the Crusade was finally deployed and the invasion began. The local road network was excellent and the Imperial advance soon neared the Tau city of Gel'bryn before the aliens were able to form a stable defensive line. With Titans and armoured formations as the spearhead, the Crusade ploughed relentlessly toward the Tau city. As it advanced, enemy missiles, fired from beyond hills and woods, started to inflict heavy losses. Units had to be detached to drive back the Tau spotters, but these were in turn engaged by Tau jump troops equipped with cloaking fields. Gradually the coherency of the attacking Imperial wedge was broken up until, by the time it reached the outskirts of Gel'bryn, there were three spearheads pushing forward of the main force. One of these was made up of Titans from the Legio Thanataris. This was countered by Tau Manta missile destroyers, the same craft that had been launched in the earlier space battles from the Tau warships. The second spearhead was predominantly veteran light infantry of the Rakarshan Rifles Regiment of the Imperial Guard, whose intelligent use of cover had kept them out of harm's way. They were countered by the emergence of a host of Kroot warriors on the rooftops and within the buildings of Gel'bryn. The third was a detachment of crusading Space Marines consisting of Battle-Brothers from the Iron Hands, the Ultramarines and the Scythes of the Emperor Chapters. These the Tau countered with their own finest soldiers -- their heavy jump troops. The timely Tau counterattacks stalled the momentum of the Imperial offensive and the front stabilised on the line of a broad river some 20 miles north of Gel'bryn.

Operation Hydra

Their advance halted, the Imperial forces, commanded in this operation by General Wendall Gauge of the Imperial Guard, had to dig in to avoid the worst of the Tau firepower. The Tau possessed superior night-fighting capabilities which they exploited, moving up to extreme range and opening fire, only to withdraw at dawn. Space Marine combat patrols with their genetically-enhanced senses helped to stem this problem, but the Imperial losses continued to mount. This was compounded by the constant worry of the Crusade's officers that a new Tau fleet would arrive; the Crusade fleet was badly damaged and could barely protect its troop transports, let alone provide air cover for the ground forces on Dal'yth. As the siege wore on, more Tau arrived at the front from elsewhere in the world each day.

General Gauge concluded that the Crusade had stumbled onto a major Tau population center within their empire and that his resources were insufficient for the task before him. Plentiful reinforcements had been promised at the outset of the Crusade but none had arrived. Inquisitor Grand of the Ordo Xenos was all for evacuation of the world followed by an Exterminatus order, as the Tau were clearly too dangerous a species to be allowed to continue to exist. Yet the Imperials had found the Tau to be honourable adversaries and there was marked opposition to such an extreme course of action within the Crusade's high command, especially from the Astartes. While the Crusade's council of war was paralysed by this internal debate, General Gauge acted. He formed his Titans up with the Brimlock Regiments and attempted to force the river line of defence down the right flank, trapping the Tau against the sea. As preparation his artillery pounded other sectors of the front and Imperial Navy fighters began an offensive against Tau airfields that was costly to the Imperial pilots but kept Tau aircraft from the front. The Imperial strike force took their primary objective in the first few hours of the offensive -- a town containing a bridge across the river to Gel'bryn -- and achieved complete tactical surprise. As the assault continued, it was countered by ultra-mobile Tau units deployed from the ubiquitous Manta missile destroyers. For the rest of the day, a running battle was fought through the Dal'yth suburbs that ended with the Imperium's troops a mere five miles away from trapping tens of thousands of Tau between the city and the sea. Overnight, the Tau troops disengaged and fell back to a new defensive line beyond Gel'bryn. By the morning the Tau were gone and while the city itself was infested with lurking Kroot, the starport on the outskirts of Gel'bryn was quickly secured by Imperial troops.

The starport, combined with the distance from the city which the Tau defenders had retreated, provided an excellent opportunity for the successful evacuation of Imperial forces from Dal'yth Prime, and General Gauge took it. Resistance from the Inquisition and Adeptus Astartes to this course of action was overruled by the arrival of an express astropathic order in late 745.M41 from Inquisitor Kryptman to return to Brimlock with all available forces as quickly as possible. The Tau sensibly realised that getting in the way of the Imperial evacuation would serve no sane purpose and parleys held under flags of truce were honoured by both sides. The first seeds of cooperation between the Imperium and the Tau Empire were sown, though these would take time to bloom in the aftermath of such a brutal conflict.

In the course of the Damocles Gulf Crusade the Imperium had learned to respect the Tau skills of war and the Tau had discovered the true scale and bitterness of a galaxy they had previously thought to just be theirs for the taking. The message from Inquisitor Kryptman had informed the Crusade command of the first Tyranid attacks upon the Imperium and within the Segmentum Command all hope of a quick victory over the Tau had already faded. It is conceivable that the Tau might have blockaded the Crusade and trapped its remaining forces on Dal'yth Prime, but as an enlightened race, the Tau saw more advantage in opening a diplomatic dialogue with the Imperium. The Crusade forces were allowed to withdraw back into Imperial space unmolested, allowing the Fire Caste to swiftly reclaim those Tau Sept worlds it had lost to the Imperium's offensive at the outset of the conflict.

Order of Battle of the Damocles Gulf Crusade

Known Imperial Forces

Imperial Guard

  • 17th Brimlock Dragoons Regiment
  • 19th Brimlock Dragoons Regiment
  • 9th Brimlock Fusiliers
  • Rakarshan Rifles Regiment
  • 4th Storm Troopers Company

Imperial Navy

Adeptus Astartes Chapters

Rogue Traders

  • Lucian Gerrit of the Arcadius
  • Korvane Arcadius Gerrit (Lucian's son)
  • Brielle Arcadius Gerrit (Lucian's daughter)
    • Oceanid (Rogue Trader Vessel)
    • Fairlight (Rogue Trader Vessel)
    • Rosetta (Rogue Trader Vessel)

Titan Legions

Tau Forces


  • Apocalypse War Zone: Damocles (7th Edition), pg. 6
  • Codex: Black Templars (4th Edition)
  • Codex: Imperial Guard (5th Edition), pg. 24
  • Codex: Tau Empire (6th Edition), pp. 13, 28-29, 34, 41, 52
  • Codex: Tau (3rd Edition), pp. 58-60
  • Farsight Enclaves - A Codex: Tau Empire Supplement (Digital Edition)
  • Warhammer 40,000 - Apocalypse War Zone: Damocles, pp. 6, 8
  • Rogue Star (Rogue Trader Novel Series) by Andy Hoare
  • White Dwarf 263 (US), "Index Xenos: The Kroot", pg. 96
  • Star of Damocles (Rogue Trader Novel Series) by Andy Hoare
  • Savage Scars (Novel) by Andy Hoare
  • Damocles (Anthology) by Phil Kelly, Guy Haley, Ben Counter & Josh Reynolds
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