The disposessed factions of the Deeps, worshipers of chaos forced out of the Deeps by the necrons and Imperium had flocked to the Arch Cleric's banner, while the Iron Warrior leader Marshall Stahl had not been slow to pick up on the growing power of chaos and the opportunity it presented. Together, the Iron Warriors, Word Bearers and the Arch Cleric had devastated much of the east of Zadoc already and the Imperium was in full retreat. This continued during late 10.013M42 as the Arch Cleric launched a major offensive to the south of Ascobabria.
The chaos forces were numerous and well equipped, once again calling on the denizens of the warp to aid their progress. Against them the Novgorod Guard were once again in evidence, as well as native Zadocian units and other hastily thrown together formations. High on manpower, low on equipment and training, the imperial forces put up an admiral defence, their commanders trading lives for time as the chaos advance fell behind schedule. Try as they might the chaos forces found it hard to penetrate the imperial defence in depth, despite horrific casualties especially amongst the conscript units.
Unfortunately for the imperial guardsmen and general Brooke, the god themselves then intervened, and suddenly the rent between realspace and the warp surged open, allowing hordes of daemons to materialise. Although this was a brief manifestation, the effects were dramatic. The Novgorod defence broke and the breakthrough could start. By 2610.013M42 the Word Bearers had reached the south coast of Ascobabria, cutting off three regiments on Gontina and making landfall on Antonerni. By 2910.013 Carelian had fallen to the dark gods and the chaos forces were moving south towards Gredau.
The continuing advance of chaos on Zadoc had not been ignored back on Vastrid. Jellicoe had been orderd to put together a fleet to reinforce the system, and thirty regiments of guard had been ordered to join the task force. On top of these Astartes companies had pledged their aid, and the Inquisition were preparing to take measures against daemonic incursion. The Dark Angels provided the most immediate support, announcing their intention to cripple the chaos fleet blockading the Zadoc system. Lord Tragaen had been joined by vessels of other warlords, bringing the strength of the fleet at Zadoc to over eleven capital vessels, but the blockade meant this force had to be split up. On 2810.013M42 the Dark Angels intercepted part of this blockading force in deep space. It is unknown how much damage the Dark Angels inflicted on the chaos fleet as they gave no record, only confirming the task had been completed and the fleet portion defeated. However this was not the only fleet action of the day.
The tau had also been alarmed by the rapid chaos advance on Zadoc. They coveted Zadoc for themselves, and as they had intervened on Tyranteous, now the tau prepared to land on Zadoc, much earlier than planned. The intention had been to allow the war on Zadoc to run on, until the invasion of Tyranteous had been completed, but with the imperium losing so badly, the tau decided to act sooner. Within days a sizeable warfleet had arrived in system, slipped through the chaos picket ships appearing near the Zadoc moon itself, where Tragaens close blockade couldn't fail to intercept them.
The tau fleet, led by two custodians, three protectors and a host of escorts, closed on the chaos fleet which had adopted line astern. With their superior range the chaos fleet achieved the first casualties, destroying half the Castellan squadron which were then forced to flee. At the end of the chaos line the two slaughter class vessels Reaver and Doomblade were caught out of position, and concentrated firepower, torpedo runs and manta attacks soon removed the two vessels from the fight, destroying Reaver.
in the centre of the battle line both Tragaen and the tau suffered from poor gunnery and disappointing ordnance attacks. the battle soon became a war of attrition as one by one the chaos vessels were put out of action or forced to retreat, with one of the carnage class vessels eventually being reduced to millions of tons of floating junk. The tau suffered too, having one custodian crippled, a protector badly damaged and the unfortunate loss of every single warden escort when they happened to drift across the gunsights of the remaining carnage and the chaos flagship.
After several hours trading blows both fleets retreated, with the tau able to claim a minor victory. Tragaen was forced to retreat in the the outer reaches and await repairs, while the majority of the tau fleet were able to push in system, establishing a base of operations on Zadoc moon. The invasion planning then began in earnest.