You and Zussman are leading a stealth mission to infiltrate the Airbase and provide cover for Pierson’s assault on the base.
Follow Zussman up the fire trail to the back part of the base. There are three points of entry here: You can follow the frozen creek to the left or right side of the base, or you can take the sewer drain to access the base.
You have two guns, a M1903 6x Optic and a 1911 Supressor. The sniper rifle does not have a silencer, so using it will alert any nearby enemies. It’s better to stick to a stealth path to avoid sounding the alarm.
Here is one suggested path:
Move down the sewer pipe and activate the grate at the end.
Continue past the truck to the halftrack on the right. This enables you to avoid the guards to the left and right.
Step into the hangar. Ignore the guard working on the plane, as he is currently distracted.
Look for the grate at the back of the hangar. Activate it and drop inside for a bonus med pack.
Objective: Kill the Base Commander (OPTIONAL)
Exit the grate and Zussman will point out the base commander. Ignore him for now; he’s too difficult to kill without alerting the guards.
Exit the back door of the hanger. Watch out for a patrolling guard. If he’s there, wait for him to pass. You can see your goal – it’s the radio dish directly ahead.
There’s a supply dugout nearby with a guard. Sneak up behind him and perform a melee kill. Zussman will kill the other guard.
Hide behind the stack of four-by-fours up ahead until the guard passes and turns his back. Wait until he is out of view of the patrolling guards and then execute a melee kill.
Watch as the base commander passes through the chain link fence. Another guard arrives to patrol the fence. Wait until he approaches on the left, then sneak between the crates and score a silenced headshot on this guard.
Now is your chance to get the base commander. Wait for the commander to walk past, then follow him by sneaking across the main section of the base. Use the tires and truck for cover.
Follow the base commander’s path into the next section of the base.
There’s an ammo truck parked here. Resist the urge to get the ammo and med packs on top of the truck. Instead, sneak up the far side of the truck and wait for the commander to circle around the back of the building.
If you did this quickly enough, you can shoot the commander with your silenced weapon to complete this sub-mission.
Wait for the far guard (near the corner of the building the commander just turned around) to turn his back. Sneak up behind him and perform a melee kill.
There’s a chance that some guards emerge on your way back to the radio tower. If this occurs, either finish them with a silenced headshot, or move around them by taking the long way back to the tower.
Infiltrated
If you can make it through this section of the level without being detected, you will earn the Infiltrated achievement/trophy. You don’t need to kill the general to unlock this, so you may want to head straight to the radar tower.