|Conflict||Third Sphere of Expansion|
|Outcome||Tau victory, continued Imperial insurgency|
|Catachan Jungle Fighters||Unknown|
The capture and colonization of Cytheria was given to the Tau Sept of Bork'an. Expecting stiff resistance, the force was supplied for a lengthy and taxing campaign. Although a sparsely populated outlying world on the Eastern Fringe, Cytheria was valuable to the Imperium due to an Adeptus Mechanicus research facility and was reinforced by seven Imperial Guard Regiments of the Catachan Jungle Fighters.
The second phase of the operation was the eradication of enemy armour and saw the destruction of the entire Catachan 97th Armoured Regiment by Tau Hammerhead Gunship 'Elimination Groups' on the third day of the invasion. As the Tau gained the upper hand, the Catachans withdrew into the jungles for a protracted guerrilla war.
In the third phase of the campaign, the Tau Fire Warriors quickly found themselves outclassed in jungle fighting and guerrilla tactics by the Catachans. Sensing a loss of momentum, Tau Ethereals redirected the attack to the Herzen Ridge and communications zone, ultimately forcing the Catachans to give battle.
The Herzen Ridge battles broke the last organized Imperial defense and afterwards Cytheria became largely pacified. Transport of materials and personnel for colonization is now well underway, and on schedule for the expansion of the Tau Empire. Scattered remnants of Catachan forces still mount sporadic guerrilla attacks on vulnerable targets in hope of eventual reinforcements. However, regular hunter patrols scour the jungles for these last vestiges of Imperial resistance.