With the UE's armies in shambles and total disarray due to poorly executed offensives, the 6th Expeditionary Legion has been deployed to assist offensives on hive cities. The first step would be to drop explosive charges down the holes where the drills came down, and even though that'd kick up plenty of debris, smoke grenades and flashbangs will also be dropped down. With any guarding troops being knocked back and injured, and farther troops recovering from flashbangs, GASI troopers drop down into the fighting. Under the cover of smoke, the forces fire at RRI troopers, still obscured from sight by the enemy. With whatever garrisoned troops that remain under suppressive fire by GASI rifles, sharpshooters and gunners take up defensible positions. Sharpshooters focus on enemy MGs, automated turrets, and other defense infrastructure. Gunners provide suppressive fire on enemy snipers, gunners, and regulars. From there it's urban warfare, something GASI is extremely good at. GASI forces will also destroy light sources, hindering the advance of enemies without night vision gear. Assuming the RRI would have enough mercy to evacuate civilians well in advance, GASI begins to deploy noxious gasses into the hive cities, which is especially deadly due to not dissipating and being directable (on account of little to no atmospheric factors). Explosive charges are used heavily to wear down enemy positions and keep them at bay, and also to strategically block off corridors and roads. The evacuating fleets would only be met with death. GASI forces and GASI controlled Narvik classes that were coming from the wormhole engage them, and they find there is no place to retreat to with forces advancing from the wormhole. These forces would afterwards return to Terminus to support offensives in that locale.