To the west, General Corchoran's combined force, known as Merrin Army Group North (MAGN), comprised of Tarsis PDF, Cadian, Zadocian and Librian regiments. In contrast to the Tau defence the Imperial Guard had dug in strongly, constructing defences in a line just south of the Noroway hills.
The Catechism considered its options and decided on a double strike,attacking Tau and Imperial assets simultaneously. Moonface's generals were gambling, in his absence, that the new "toy" he had given them would prove most decisive. The devices Moonface had gifted his generals were in fact daemonic artefacts, forged in the warp itself and given to Moonface by an unknown greater Deamon of Tzeentch. Moonface had made a pact with the Daemon that if his forces merely agreed to attack and slaughter targets of his and his generals wishes, they would be able to assume a corporeal form for a temporary period. This the devices, acquired by Moonface over many long millenia, would make possible.
With the pact in place the forces of the Catechism first moved into Tau held territory, just north of New Southwick. The Tau immediately detected this attack and prepared a limited response. Though numerous the Chaos forces were ill equipped and not backed up by Marine Legions. Shadowstrike,unaware of the Daemonic pact, determined the greater threat still lay with the Imperium, and continued with his planned assault on Montgate to the north, providing only a limited number of Hunter Cadres to meet the Chaos threat.