On 2002.009M42 Shadowstrike called his other commanders to a hasty planning meeting. With the catechism gone resistance in the north was seen as weak and the Tau commander had identified an opportunity to make major gains against Chaos for the first time since the start of the war. With the strategic situation in relation to the imperium the best it had ever been following the capture of Sapphire Harbour it was also a good time for a major push in the south. All tau cadres were mobilised and preparations made for operation Poseidon, with the aim of rolling back both fronts and making major gains in a lightning Blitzkrieg.
Assault on Chaos
After his successful attack out from Sapphire Harbour Elan Ro was once again mounting up his force into Mantas and relocating. This time he was placed against what remained of the Chaos forces. While he’d been off planet the might of Chaos had crumbled, and Shadowstrike intended to capitalise on this.
What Elan Ro found was an entrenched force of Iron Warriors ready to try and repel his advance. His mechanised units moved forwards and Stealth units in advance of the main force began to harry the defenders. The Iron Warriors were lacking in long range anti-tank weaponry, only as small contingent of Predators, which were suppressed and then systematically annihilated.
As ever however Shadowstrike had chosen well in his selection of the conservative and patient Fastblade. The Tau commander moved his forces to the endge of the city by night, minimising casualties, then began the methodical process of destroying the Iron Warriors, and much of the city, with indirect firepower.
Closing the Gap
It was actually the advance by Or'es Kair, the least experienced commander, which started the momentum of the Tau in the south. Shadowstrike had called for a limited encirclement against the mighty river Fuller, but as Kais moved her forces forward, she found the defences rather lighter than anticipated. Cautiously the Tau continued to advance, but critically, kept their flanks from being exposed. Then the Ultramarines sprung their trap.
Following the dramatic and astonishing advance by Or’es Kais, the Tau brought forward their timetable, moving their forces quickly and efficiently, deploying Elan Ro’s main force, which has been in the north, south to take advantage of the lightning advance, not allowing Cochrane’s battered forces to regroup.
Operation Poseidon eventually ended on 0603.009M42, not because of effective enemy resistance but because the Tau were exhausted. There were no more fresh cadres to throw into gaps in the enemy lines and supplies of ammunition and fuel were almost exhausted leaving the tau incapable of mounting further offensive opperations for the time being.
General Cochrane meanwhile was stuck, defending a small pocket of ground on the Merrin coast with just over five divisions. His supply lines untenable, he was still expected to fight to the last. The force, mainly Trebbian and Librian, was ordered to reject the surrender terms proposed by Shadowstrike. Cochrane then attempted to negotiate a withdrawal from Merrin.
Elan Ro was keen to accept this, but Shadowstrike overruled him. He could not allow five divisions and their equipment to be redeployed as they would need to face them again in subsequent fights. The negotiations were ended and the Tau prepared the final massacre.