Outer World Assaults

With news of the Monarchy's withdrawal, the Diabs, three years after the Second Battle of Baltreos, mustered troops for another major push into the Pact foothold. With large-scale frontal assaults having proven too costly, the Diabs planned to attack the Foothold's "northern" flank, which was comprised of what had been several outlying colonies prior to the invasion. Once these colonies were retaken, the Diabs would then strike at the Pact's fortified logistics facilities, which were principally located at Sevethos and other nearby colonies. If successful, the operation would cut the foothold off from much-needed supplies while also drawing forces away from the front line, at which time the Diabs could open a second front.

Diab forces first attacked the gas giant of Glasos, which the Pact had been using as a local source of fuel for their energy weapons, and its many moons. Alliance forces quickly overwhelmed the planet's orbital defenses and simultaneously landed on a number of the inhabited moons. Pact forces initially resisted, but after days of fighting, it became clear that they would not be able to hold their ground, and withdrew to Glasos itself. Another round of fighting would see the Diabs victorious, but much of the planet's infrastructure would be destroyed, as the Repzork had rigged many of the gas-harvesting stations to self-destruct and plummet into the gas giant.

From Glasos they advanced towards Alavinos, which had by then been reinforced from troops from within the foothold and Glasos' garrison; however, reinforcements were not as plentiful as they could have been, as Imperial Command correctly predicted that the Diabs would open a second front, but did not know when, and as a result withheld troops for an attack that would not yet materialize. Diab forces successfully achieved orbital and aerial superiority over the planet, trapping Pact forces in their underground fortifications just as the Pact had done to the Diabs during Operation Sledgehammer. Fighting erupted through the underground tunnels as Repzork ships attempted to break the siege. Stiff resistance would delay the Diabs longer than planned, but after five months of fighting, Alvainos was liberated.

The last obstacle to Sevethos was Urdos, a planet which had suffered a particularly severe crystal infestation that rendered large swathes of the planet almost completely uninhabitable. Travel between the Repzork's scattered fortresses was possible only through narrow passages through fields of crystal or an underground railway, as imperial forces had built the bulk of their facilities at least partially underground so as to both avoid the crystals and to harvest ore. The Peacekeepers attempted to subdue the planet through aerial bombardment, but were repelled by constant anti-air fire, forcing them to commit to a ground assault through the crystalline labyrinth. Concentrated artillery fire combined with constant harassment from Pact troops trained to navigate the terrain frustrated the Diabs' effort. As the battle stalled, the Peacekeepers opened their second, larger front near Falkeos, forcing the Pact to divert troops to contain the threat. This did little to shift the Urdos campaign, which would remain at a stalemate until Diab forces were able to eliminate enough of the Pact's anti-air defenses to allow for bombardment. Not risking a repeat of Alvainos, Pact forces retreated, but not before the Peacekeepers captured thousands of demoralized prisoners.

With the path now open, Diab forces moved towards Sevethos, which alongside a sizeable garrison, was also guarded by several depleted Repzork and Magellan formations that were in the process of replenishment. Fierce fighting broke out throughout the system, but it would prove short-lived. Though Operation Counterweight had started three weeks prior to the battle, Marshals Ilivaris Kindasi and Veto Korvack pressured the rest of the Marahal's Council, who were focused squarely on repelling the Karahotdoum threat, to relieve the foothold with what were seen as troops desperately needed for Counterweight. High Marshal Tarsovis Visaria believed that Pact forces could hold their ground, but upon hearing of conflict at Sevethos, authorized a task-force to accompany a fleet of Necraal and Magellan ships entering the region. This task force included the Helia-Class Battlecruiser, the HLBC Nygalara. The relief force caught the Diabs by surprise and successfully repelled them from the system after nine hours of fighting. With the attack at Sevethos a failure, the second front was called off. Urdos, Alvainos, and Glasos were all abandoned by the Peacekeepers and fell back into Warlord hands.