Mission 3: Price Airfield
After following Grim's charade and faking an escape, open the gated door and quickly get to cover, as a single sentry's patrol route covers this initial area.
Pick up some C4 before you enter the hangar.
You know what the objective entails: get some C4 and do it stealthily. The C4 charges are located just ahead under a small canopy. The only problem is that two live guards stand near them. This very minor hindrance is easily surmounted by gaining an Execute from the first lone guard and then using it to put down the two aforementioned guards. Upon picking up the C4, Grimsdottir tells Sam to plant them on the chopper in order to prevent them from foiling his escape. Take the charges and head towards the building.
The chopper sits cold in the brightly lit center of the hangar and is surrounded by approximately six or seven guards. The hangar provides many angles of approaches with its copious pipelines running along the ceiling, its hanging turbine engines--to name a few. From outside, head up the stairs leading up to the hangar's entrance and quietly open the door. Just on the other side of the door is a guard peering over the hangar with his back stupidly turned toward Sam. Assassinate him and leap over the rail to shimmy over to the left-hand side (from a hanging position, it's to the right). Looking ahead, you should spot an engine turbine strung up on a thick chain. Shoot the turbine loose to let it crush the two guards standing underneath it. Naturally, this heightens the others' alertness and causes them to sweep the region to investigate the cause. At this time, Sam should be able to Execute a couple, leaving just a few more stragglers. Some patience should open up an opportunity for a Death From Above. When only two are left, mark them and Execute.
Afterwards, approach the chopper and plant the C4.
Disrupt the power relay in one of the barracks.
The barracks ahead teem with guards, but the ones on the left side can be ignored completely. Move to the far right to reach the first barracks and an opened window. A soldier should appear shortly if he hasn't already to work on his computer. Take him hostage and black him out among the bunk beds, then turn off the lights. Sneak out the window so that ultimately Sam travels between the barracks and the fence. After the next barracks, two guards stand outside, one of whom is facing Sam's direction. There's no other way to get by these guys without killing them, so plan the Execute. Very carefully creep in through the window of the last barracks if it's clear and turn off the light switch. This should spook the sentry standing guard just outside one of the doors and prompt him to come inside. Thwack him on the head and leave through this door.
The target barrack is the adjacent building and boasts a trio of armed guards. They're all ready to pepper any intruders silly enough to burst through the front door. Make some noise outside to draw some of them out for takedown and Execute any stragglers. After successfully disrupting the power relay, head on through the gated door nearby for further instructions from Grim.
Plant C4 charges on satellite dish to prevent tracking.
With the mysterious power outage, guards everywhere have been alerted to Sam's presence and are wired to search and destroy. Guide Sam past the first opening to the hangar, where a guard briefly patrols this area. Instead of breaching the building from this opening, head to the opening that is slightly obscured by the drapes. This area bathes Sam completely in shadows, giving him the freedom to blow out the lights as he inches up. Be very wary as he does so, as the area is crawling with copious number of armed personnel. The idea is to move up, past the plane, then to the far right, and up. This definitely is easier said than done, but use your wits to overcome this. Some tricks to use: shoot at an area only once (twice at most) away from where you intend to lead the guards astray. While they're distracted, Sam can slink along the shadows and reach the satellite dish.
Don't be afraid to use Executes, and above all, take your time. After securing the charges on the target, more hostiles begin to converge on Sam's position. Quickly duck into the nearby hangar and move from cover to cover to avoid a bulk of the enemies.
Destroy the gate security system at the guardhouse to prevent anyone from following you.
The author was unable to avoid a loud confrontation with all the enemies in the next part. The next area's bright lights and full moon aren't conducive to being sneaky, so perhaps deploying Frag Grenades and well-timed Executes in lieu would be the best bet. There are a respectable number of enemies here, allowing Sam to be easily overwhelmed and gunned down. Be careful. The target is the guardhouse against the far end. Hit the switch in the guardhouse to gain access to Grim's car.