Taros Campaign

The Taros Campaign was an Imperial military campaign fought by the 4621st Imperial Guard Army and elements of the Adeptus Astartes to reclaim the Imperial mining world of Taros from the Tau Empire and its Kroot and human (Gue'vesa) allies of the Taros Planetary Defence Force in 998.M41. The campaign was ultimately unsuccessful and Taros remained in the possession of the Tau, who renamed it T'ros.

The Denab Incident
While on a routine anti-pirate patrol in the Denab System of the Ultima Segmentum, the Imperial Navy Patrol Group Ravanor, comprised of the Dauntless-class Light Cruiser Lord Ravanor under the command of Captain Darillian and four Sword-class Frigates, chanced upon three unidentified human ore transports. The discovery of these starships eventually led the patrol to an unexpected Tau waystation where the human vessels were off-loading their ore to sell it to the Tau Empire rather than tithing it to the Imperium of Man, which desperately needed all the raw materials it could get its hands on to prepare its miltary forces to face Abaddon the Despoiler's coming 13th Black Crusade.

After a brief engagement with the Tau station and a boarding of the errant human vessels, it was discovered that the last port of call for the transports had been the Imperial mining world of Taros. Upon his return to his station Captain Darillian filed a full report with Ultima Segmentum Command on this illegal contact between the people of Taros and the Tau xenos.

When Auditor Prime Dree of the Adeptus Administratum who had been tasked with locating more strategic minerals for the Adeptus Mechanicus Forge World Stygies VII, which was churning out needed military supplies for the Imperium's coming war effort, discovered the report detailing the Denab Incident it confirmed the suspicion that had been engendered on a previous ivesitgatory effort to Taros that the world's planetary government and wealthiest merchants were illegally trading away some of Taros' strategic minerals to the Tau rather than providing them to the Imperium for their own profit. Dree filed his findings in another report to the Administratum, which then requested through the Imperial Guard's Ultima Segmentum Command that the closest Chapter of the Adeptus Astartes, the Avenging Sons, deal with the problem. Once the Planetary Governor of Taros, Uphir Aulis, realised that the Imperium was going to take action against his world for their illegal trading following the Administratum's audit of his world's mining production quotas, he openly requested the military intervantion of the Tau Empire and allowed the Tau to annex the world in return for their protection from Imperial justice for himself and the other members of the Tarosian elite who had violated Imperial law by trading with them. Unknown to the Imperium, the Tau then placed a relatively large defensive force on the world to supplement its own Tarosian Planetary Defence Force units.

The First Taros Intervention and the Taros Campaign
The Taros Campaign of 998.M41 pitched Imperial forces from both the Imperial Guard and two Chapters of the Space Marines against the human Taros Planetary Defence Force, the Tau, and their Gue'vesa and Kroot mercenary allies in a series of battles across the surface of the desert mining planet of Taros (renamed T'ros by the Tau after their annexation). Prior to the campaign, the Imperial Planetary Governor Lord Uphir Aulis, the head of the Taros planetary govenment, developed friendly trading relations with the Tau who desired Taros' strategic metals to build up their own war machine. Ultimately the governor sought to defect with Taros to the Tau Empire with the support of much of the planetary population once his illegal trading with the xenos was discovered by a team sent by the Adeptus Administratum. The Administratum had sought to determine if the planet's tithe of ore could be increased to meet the growing demands of the Imperial Guard for military materiel to prepare for the expected 13th Black Crusade of Abaddon the Despoiler. When Aulis' treachery was unveiled, a full company of Avenging Sons Space Marines were dispatched to kill him, but they failed in their assignment after being intercepted by a relatively large force of Tau Fire Warriors who had been secretly assigned to the world to protect the governor from Imperial intervention. They were unprepared for the sheer size and ferocity of the Tau forces on Taros and were forced to make a fighting retreat after their assault on the governor's palace in the capital city of Tarokeen led to heavy casualties, including the loss of a Dreadnought. Following the assassination attempt, the Tau officially annexed Taros while the Imperium responded by creating the 4621st Imperial Guard Army made up of several regiments of the Imperial Guard to recapture the planet. A second Space Marines Chapter, the Raptors, also committed two companies to the effort after the Imperial Guard had become bogged down. A large-scale invasion of the desert world followed, including fleet actions between the Imperial Navy and the Tau Kor'vattra ending in the defeat of the 4621st Imperial Guard Army and elements of the 3rd and 6th Companies of the Raptors Space Marine Chapter. The Imperial forces were forced to retreat from the world after suffering heavy casualties that made further prosecution of the campaign impossible, including the loss of 5 full regiments of Imperial Guard troops, a Warhound-class Scout Titan and several Imperial starships. This defeat is partially credited to the traitorous defection of a large percentage of the human population of Taros to the side of the Tau, including the Taros Planetary Defence Forces. Taros then became T'ros, a Sept of the Tau Empire's Third Sphere Expansion and its people are now considered Gue'vesa citizens and T'ros' ores go to serve the Fire Caste's military.

First Taros Intervention (Imperial Forces)

 * 1st Company, Avenging Sons Chapter
 * 2nd Company, Avenging Sons Chapter

4621st Imperial Army (Taros Campaign)

 * X Corps
 * 17th Tallarn Desert Raiders Regiment
 * 89th Tallarn Desert Raiders Regiment
 * 331st Tallarn Desert Raiders Regiment
 * 3rd Tallarn Armoured Regiment
 * 12th Tallarn Armoured Regiment
 * 2356th Storm Troopers Company
 * 2378th Storm Troopers Comapany
 * XI Corps
 * 23rd Elysian Drop Troops Regiment
 * 11th Sareinnian Assault Engineers
 * 114th Cadian Shock Troops Regiment
 * 19th Krieg Armoured Regiment
 * 8th Brimlock Dragoons Regiment
 * Adeptus Astartes Support
 * 3rd Company, Raptors Chapter
 * 6th Company, Raptors Chapter
 * Collegia Titanica Support
 * Legio Ignatum Warhound-class Scout Titan Battlegroup

Tau Forces

 * Tau Fire Caste Taros Army
 * Kroot mercenary units
 * Taros Planetary Defence Force
 * Taros Mining Work Gangs (Irregulars)