Nevada Desert
Drop Off
After getting dropped on the roof here, hit the refit boxes and nab the SR-25 SD sniper rifle. It's silenced scope will help you make a stealthy approach towards the refinery. Match it up with something powerful, like an assault rifle. Silence will be your ally here, so be sure that you're going to be capable of silencing your alternate weapon.
When you drop off, slide down the ladder and into the room below the roof. Head through the door and go through the door in front of and to your right. That will lead you to a window that you can quietly open climb through. Hiding behind one of these dumpsters will let you start firing on your foes with your silenced weapon, hopefully allowing you to finish them off without alerting them. Even if they do catch on, though, you'll still be well protected behind the dumpsters.
;)
With the restaurant somewhat clear, move over near the burning truck and start sniping at the enemies that appear after the checkpoint. A soldier will man the turret in the guard house, another will walk up near the truck, and a few more will be in position in the refinery. You can snipe all of them. Switch to night vision if you need a bit more contrast in your view; that should help you pick them out.
As you make your way into the refinery, silence will be less important, if not irrelevant. There's only one path to take, and you'll have to walk around a corner into a shooting gallery. There isn't much to do but switch over to your assault rifle, take off your silencer, and start going to town. In your favor, you can hide behind the concrete pillars here to shrug off most fire, and you can fire upwards through the catwalks to hit your opponents. On the downside, there are a lot of them (including a tough-to-spot sniper high on one of the smokestacks), and some of your foes will throw incendiary grenades at you.
;)
Your best bet here is to rile up the first group of opponents, then backtrack to see if the two enemies on the ground floor will come after you. If they do, dispatch them; if not, try to get them from an angle where the enemies above can't see you. With that done, crouch down and use the ceiling for cover until you can take down the enemies above one at a time. When they're all dead, sprint forward and to the left, winding up near where the shotgun enemy first stood. You'll be behind a brick wall, with a ladder off across the area. Switch to automatic fire here and kill any enemies that come down the ladder or up the steps to you. If you can do that, you'll have a few more enemies to kill near all the barrels in the middle of this area; use grenades.
Apart from that, the remaining enemies will include a turret gunner (snipe him from long range), and a few straggling enemies. Make your way to the checkpoint near the gunner to reach the next area.
Furnaces
Whip out your silenced sniper rifle for the trainyard. At the outset, there are three enemies wandering up and down the trainyard in between the trains, so snipe them from a distance. Move towards the checkpoint after that, taking the path along the leftmost wall. When you're around 15 meters away, two more enemies will appear, including one that will patrol along the left passage. Snipe him, then find the other one on your map and take him out too.
;)
The boiler room nearby is more easily infiltrated from the ground floor than from up top. Getting on the walkways also increases your chances of getting shot from below. You're near a checkpoint, too, so you don't need to worry too much about keeping quiet, although it can definitely help. There should be four soldiers in this area, perhaps five. Take them out and move on.
After hitting the checkpoint, your goal will be to shut down the fire alarms. The next large room has a bunch of enemies in it. Head down the stairs and open the doors down there; it's easier to shoot upwards through the catwalks than it is to fire down below, and you can also use thermal imaging to find some of the enemies that hide from you. The enemies here have a harder time detecting your presence, presumably because of the sound of the fire alarm.
One more building awaits you on your trip to the refinery. Check the door with a snakecam, and you'll see two enemies. One will be directly in front of you, and one will be off to the left. You can pop the door open and silently kill both of them without a problem.
Refinery
As soon as you hit the fire alarms here, the enemies nearby will be alerted to your presence. Move back towards the doorway you entered the room from and use your assault rifle on any enemies that come through the door. Your sniper rifle can be used on the two turret gunners that fire through the windows. With them taken out, start making your way out the now-opened door leading on.
There are two paths that you can take here after exiting the door. You can move forward and to the left to wrap around the buildings and down into the parking lot, or you can simply duck down behind one of the sheet metal barricades in the railings to provide cover while you kill off all the soldiers near the vans.
When you reach the next checkpoint, just after killing the soldier that's on the walkie, you can go silent again, as the soldiers beyond him will be patrolling. Take as many of them out as you can without making noise, then go for the rest with everything you have.
;)
There are two entrances to the refinery, either up the ladder or down the stairs. We preferred taking the loud route and heading down the steps, opening one of the doors there, and blowing something up. That'll bring plenty of soldiers down near the doors, where they'll be pretty tightly packed and easily killed with a grenade or two if you stay on your toes. Move on from there up the stairs towards the checkpoint, but be aware that the last room before the checkpoint will have numerous enemies. You'll be pretty close to a refit box, though, so feel free to use up your grenades on these guys.
At the refit station, you may want to grab flash grenades if you want to remain silent; otherwise just gear up for more loud firefights. If you do have flashers, you can open the double-doors on the opposite side of the first large room, chuck a flash in there while both enemies have their backs turned, and gun them both down with a silenced weapon to move on. Make your way down to control room two to reach the last part of this mission.
Airstrip
The first portion of this area will be more sniping. Check your map to see the locations of enemies that you might not be able to detect visually and take them down with your rifle for good times. As you approach the far building, though, be prepared for a full-on counterattack.
Eventually you'll reach a hangar. Fastrope down into it for a cutscene and to end the mission.
