Now to reach the command bunker. Fulfill your destiny and grab the chainsword for maximum glory. A green mob will assail you, so put some bolt rounds into neutralize upper level shootas and chainsword anyone who gets close as you move through the trench. Take a right when you reach the fork in the trench. You’ll be introduced to suicide critter, the bomb squig.
You should see two dead Imperial Guard troopers. To the right is some ammo behind a flammable object (red explodey things). Get back to the guardsmen bodies and take the higher ground. There’ll be bomb squigs in the trenches below you. Shoot them at a distance. Next, there’ll be bomb squigs and gretchin, shoot the squig to take care of the whole group.
After the Ork ship flies by, pick up the grenades from the ammo stash and either use them or the explosives to get rid of the oncoming shoota wave. This should lead to another Ork wave. Go left to the sealed door; nearby a group of guardsmen will be making a desperate stand. Impress them by dispatching Orks with ranged weapons. Use the chainsword if the bloodlust takes you, but you will be constantly under Ork fire, so your armour will suffer and may not get the chance to regenerate.
One wave is succeeded by another, this time the Orks have brought a slugga nob (i.e. big, tough Ork). Soften him up with bolt rounds and grenades then follow-up with shoulder bash or foot stomp combos. Hack away when he’s reeling until the execution sign comes up, then get ready to struggle with him.
After the nob is dead, run to the sealed door by the guardsmen to trigger a conversation which leads to it being opened. Proceed inside, turn left and down the stairs.
Continue forward to meet 2nd Lieutenant Mira. There’ll be a support pod to the left of the stairs. Collect the purity seal to unlock Fury. This increases your melee attack damage, and allows you to execute enemies at any time, even nobs, and constantly regenerates health. You charge Fury by performing your sworn duty (killing stuff).
The door to Mira’s right will unlock after you collect the purity seal. Follow her to the front lines. Once you get to the barbed wire, enter the second bunker, past your expected path to the objective, and pick up the third audio log (Medicae Station Ventris 1/5). Turn around and take your first left to trigger Orks making good use of their digga. Now’s the intended time to use Fury, but you can get through it without using it and it may be useful later.
Head to the ammo stash on the right, through the archway, and drop down into the complex on your left. Kill the Orks, then follow the sounds of battle to kill more Orks, picking on your guardsmen buddies. Be warned, if you shoot the explosive hazard, the guardsmen will die too, and what kind of protector of humanity would you be then, hmmm?
Go right and man the Heavy Bolter. You can tear it off its mountings, but it does overheat. If you saved the Fury from earlier and the Orks are proving troublesome, now is a good time to use it.
Head towards the building on the right and deal with the Orks. On the left is another support pod. Pick up the Stalker Bolter for some hot crosshairs on Ork action (it’s a sniper weapon with a powerful shot, but low ammo capacity). Proceed into the ruins.