Tarlius II: Chaos smash Crusade

Having opened up a front against chaos and the loyalists on Tarlius III, the Grey Knights were far too small and valuable a force to be spent on garrison duty. In order to maintain the Crusade presence on the world the Sky Lords also sent a company, to act as a rapid reaction force, while Cybixx sent a small but effective force of Mechanicum and Skitarri. Crucially however the Crusade were unable to call on their Guardsmen regiments to hold a wide front, as the Volscians were still en route from Vandrax.

Having only elite forces defending their bridgehead on Tarlius II, the Crusade were vulnerable, and the forces of Chaos took advantage of this weakness with devastating results in late 02.018M42 into early 03.018M42. Using weight of numbers, the forces of chaos attacked on two fronts, with the forces of the Death Guard and those of Magnus joining forces in a concerted effort against the dangerous crusade.

Mortarion himself architected the assault by the 1st Plague Company, targetting the strong Adeptus Mechanicus forces near the landing area controlled by the crusade. Meanwhile the Emerald Serpent, led by a shard of the daemonic entity known as "Magnus the Red" fell upon the Sky Lords.

The Death Guard found the going tough against the Mechanicum, but heavy fighting led to the plague God's victory, as the traitor marines and pox walkers wore down even the toughest machines as well as the flesh. Meanwhile against the Sky Lords, although Magnus was all but executed early on by massed lascannon fire, confused communications between Cybixx, the Sky Lords and other Crusade factions led to a fiasco of orders for the astartes on the ground. First the Sky Lords were ordered to simultaneously hold the line and advance on the enemy, and later, while the thousand sons were hunkered down in the ruins of an Imperial base, the Crusade force was ordered to pointlessly launch wave after wave of their own men against the fortification, whereas simply cutting the chaos force off would have won the battle.

The result of the poor comms and negative outcomes of both engagements led to the crusade finding themselves in an untenable position. The crusade base on Tarlius II was evacuated on 0703.018M42, leaving the loyalists and chaos forces to fight it out.

To prevent any union of Imperial force on Tarlius II, the Emerald serpent also launched an assault lasting many days against Patreus' Novgorod army in the southern wastes. However the results of the engagement were inconclusive, as winter storms in the southern hemisphere called a premature end to the fighting. By mid 03.018M42 however, control of the vast plains of Tarlius II was roughly evenly split between loyalist and chaos forces.