When the mission starts, you're in the water. Run along the water's edge and head straight for the center of the last 2 barricades on the beach. You'll end up swimming part of the way but that's okay because the guards patrolling the shoreline won't see you when you're in the water swimming.
Once you reach the other two barricades, run up to your left and up the hill just to the end of the razor-wire. Don't run ALL the way up the hill else the guards will come to investigate. Crouchwalk up the rest of the way and be careful of the razor-wire!
Once past the razor wire, stop at a position a few yards on the hill and get out a grenade. Look at your map computer and watch the two guards below your position. One is patrolling and the other is standing still. Use your map computer to align yourself so you are facing a position just behind the guard who is standing still. Get out your grenade and when the patrolling guard gets close to the other guard, bounce your grenade off the hill's edge right in front of you and it'll go down the other side. Switch to your map computer again and see if the explosion takes out both guards. If you timed the grenade just right, the explosion kills them both.
Now, put your map computer away and run to your left partway up the little hill. Crawl over the top of the brown hill because the sniper below will see you. Crawl to a position so that you are on the hill just even with the end of the camoflage tent. Take out your binoculars. Zoom in on the sniper's head and pluck him straight through the side of his head. You won't see him fall but you'll hear him fall.
Now, turn your attention to the guard in the middle of the open area behind the sniper's tent. Do the same thing with your binoculars. Zoom in on this guy's head (tough shot!) and fire. It's difficult to see if he collapses. If he's still standing then do it again but this time aim lower and put two shots into his chest. You have to take this guy out quickly and quietly to complete this mission. If this guy starts running around crazy then you might as well start over.
Now, crouch and take out a grenade. You are going to make one perfect grenade toss and kill the 3 guys guarding the generators. What I did was practice this grenade toss alot. I used my aim-dot for the grenade and I aimed right at the middle part of their gate. Then, I raised my aim-dot until it was just about even with the top of the mountain in the distance. Then toss the grenade. It should land just about where the 3 guards are standing and take them all out in one explosion. Check your map computer after you toss the grenade to make sure that these 3 guards go down..
You have to act quickly now. The explosion causes the guard patrolling by the fuel tanks to stop and look around. Lay flat with your sniper rifle and quickly drill the guard by the tanks before the other 2 guards in the back tent haven't yet come to investigate. You have to act fast.
Once you've sniped the guard by the fuel tanks, the other two guards will be just heading your way coming down the middle area by the fence gate. Use your last grenade. You have to toss it in front of the two guards so it bounces and explodes and takes them both out before they turn and run. Thoss the grenade ahead of them and let it bounce. Make sure that these guys are dead. If one survives, drill him with the SMG.
Now, get up and RUN down the hill. Toss your sniper rifle. Unlock the fence gate. Turn off the motors. RUN up towards the next area.
Here's the trick. Run off to your LEFT and along the base of the hill and while you are running you need to use your heat-vision goggles to check on the guard patrolling back and forth. As you approach the razor-wire barrier, if the guard patrolling back and forth is walking away from your position or is way off to the right then you can crouchwalk around the end of the razor-wire and along the base of the hill into the trench. Otherwise, you'll have to crawl most of the way around the razor-wire into the trench. I've even walked completely around the end of the razor-wire right into the trench when the patrolling guard was way off in the distance. The guard by the tent with the grenade launch doesn't get excited unless you're making alot of noise.
Once around the razor-wire and into the trence, crouch walk a little ways along the bottom of the trench then RUN the rest of the way but keep a keen eye on the guard in the window directly ahead. When he is not in the window, run. If he is in the window, lay flat. Get to the small hill at the end of the trench off to the right and lay flat on the side of that little hill.
Use your binoculars to get a general position for your aim at the head of the guard in the window. Get your silenced weapon ready and when the guard appears back in the window and stops for a moment, fire a clean headshot right at the guy. Hopefully, you'll pluck him with a single headshot. If you miss, he stands there for a moment startled so you have a small window of opportunity to quickly drop him with a second shot. If you miss the second shot, he comes running outside and you'll have to kill him quietly. I've missed this guy quite a few times but managed to put the second shot clean through his head and he collapsed without causing any commotion. Take this guy out!
After you've plucked the guy in the window, crouch walk to your right around the building to the front door. Don't crouch walk next to the building! This causes the guard on the other side of the wall to come out to investigate. Be sure to crouchwalk on the dirt-side of the trench around to the front door.
Crouchwalk straight up to the front door and open it. Crouch walk right inside and head along the wall right under the window and to the backend door. Open the door then walk over to the machinery and disable it. You have to act fast now.
Turn and walk back to the door of the room with the machinery. Crouchwalk straight out the way you came in and out the front door. Be sure to close the door behind you because you're now going to stand up and run and one of the guards in the door-area might see you. Once outside with the door closed, stand up and RUN straight to the backend of that building and along the hillside. Keep running. The trick now is to get up to the other compound BEFORE the guards exit the helicopter and get up to the compound. Here's how you do it.
There is one big hump of grass which you will go over along the hillside partway up the road. At the top there is this flat spot. About 3/4 the way past the flat spot there is one small little part of the hill which you can run straight up. It takes some practice to learn just where on that hill you can run up but once you figure it out, make a bee-line for that part of the hill and run up. This only leads to another flat spot and you have to find the second spot where you can run up to the top of the hill. Go Left and the second spot is right in front of the tree at the top of the hill off to your left. Run left and then straight up the hill towards that tree. Again, this too may take some practice.
If you've done everything right, you've run up the first part of the hill then doubled-back and run right up the second part of the hill. Now you're up on the top of the hill but you have to keep moving because the guards are quickly head to your position!
Once facing the tree at the top of the hill, run LEFT then make a bee-line straight for the side of the front building with the door and WALK the rest of the way straight around the barricade and to the front door. Quickly open the front door and crouch..
You should've made it up the hill and now are inside the door BEFORE the guards from the helicopter have reached your location and nobody saw you.
Get out your silenced gun and make sure it's on single-shot. Crouch walk up to the inner door and open it. Before you enter that area, you have to snipe the guard standing right there in the side of the head cleanly. Otherwise, all hell breaks loose. After he collapses, crouchwalk in and don't worry about the guard down the right corridor. Head straight for the guard at the end of the hall. About 3/4 the way down the hall, crawl the rest of the way and get behind this guard. Don't worry about the guy down the left corridor because he won't see you. Break the first guard's neck!
Now, crawl backwards a bit and get behind the boxes right there. Turn and aim at the guard down the short corridor and take him out with one headshot. This shot is also critical. If you miss then he'll immediately start shooting right at you! Take him out quietly and with a single shot.
If you've done this part right, the guard standing on the other side of the door doesn't know a thing. Now, crawl from behind the boxes and get in a position so you can put a single shot into the back of the guard's head standing on the other side of the door. You're going to take this shot straight through the window. Don't crouch walk else he hears you! Stay crawling until you've taken him out. Don't miss this shot either.
Once the guard inside the door collapses, you can stand up and walk to the door, open it, and WALK to the machine and disable it. Don't RUN because the other guard still alive down the other corridor will hear you and come running and see you just before the mission timer ends!
This is a fun mission but it gets frustrating because you have to do so much right. And the toughest part of this mission is the 3 back-to-back grenade tosses at the beginning to get past the first area. If either of your grenades don't take out their intended targets then you'll never finish the mission in time.
I did this mission in 6:23 without being seen and 100% accuracy.
Tough mission but you can do it.