As soon as you gain control of Karl Fairburne, follow the path, picking up the mines on the box to your left. Your objective is to find a way into the Fort, so move forward until you come out on a platform with a rope railing. From here, whip out your binoculars and look to the east. You'll see three guards, and on the cliff behind them, your next destination and first sniper's nest.
You can avoid the left or west side of the map entirely. There are bad guys over there, but as long as you don't get spotted or alert them, you should never have to worry. Climb down from your wooden perch, then head to the east, sneaking up on the guard manning the machine gun. At some point on your travels, you should get an optional objective to disable the searchlight towers. Continue heading east, using your Welrod to kill the other two guards below the sniper's nest.
Approach the generator and sabotage it, then head up to the sniper nest nearby. If you're not exactly sure where it is, it will show up on your radar as a white icon with a flat bottom and two points sticking up on either end. Enter the sniper's nest and get comfy. You're going to be here for a minute.
From this location, you will be able to disable both of the search lights. One should be in front of you, while the second is off to the west side of the map. Wait for the generator to go haywire, bringing up an icon that indicates your shot will be masked. Rather than shoot out the light, take out the guard in the tower first, then the light with your second shot. Repeat this process for both towers. Be aware, you must hit the illuminated portion of the light and not the side. When both searchlights are down, you'll have completed your first optional objective, disable the searchlight towers.
Now look up to your primary objective about 180 meters away, then just to the left where you'll see a row of windows. The third window from the right will have an officer. Take aim, wait for the generator to mask your shot, then put one in this guy's skull. While it's not an objective, this will complete the Long Shot challenge for this mission.
In front of you, there will be a series of four tents with one of the search towers behind them. To the right will be a campfire, and if you haven't shot them already, a couple of guards. Your next path is going to take you directly past that campfire, so use the generator to mask your shots and clear out any of the guards roaming around that area. With the path clear, head down past the campfire and cross the road, making a mental note of where you crossed.
Tip: We opted to use the sniper's nest to take out about 15 soldiers, but it's not necessary. Still, move slowly and keep an eye out for stragglers. There are a lot of bad guys in this part of the mission. There's also a truck that patrols up and down the road, so don't stay in the open for too long.
You should come to a rock face that has some white paint on it. Climb up here, but be careful of three guards to the northwest (left) when you reach the top. You'll also notice some scaffolding to the northeast (right) when you read the top. The scaffolding is where you're going in a few minutes.
Head left to where you'll see three guards patrolling along a path with a fire. Crouch behind the sandbags and you should be safe, but one guard will come dangerously close to your location. From here, you have a couple of options. You can try to shoot them all with your Welrod as they are split up, or you can toss a grenade into the fire as they are all huddled. We went the grenade route and took out the whole lot of them in one go.
Move to the table next to where you threw the grenade in the fire. On there, you'll find some documents that when collected, will update your optional objective to assassinate the officer as he drives past the Fort. Immediately double back the way you came, going down the rock face where you climbed up. Once you reach the road, lay down either S-Mines or Land Mines, then move off the road and wait. When the truck passes over the mines, you'll complete the objective to assassinate the officer as he drives past the Fort.
It's now time to put the outside of this mission behind you and get into the fort. Head back up the rock face that we spoke of, then head to your right and climb the scaffolding to get inside. This will deliver you to the main courtyard. Crouch where you began, then spend a few moments getting yourself acquainted with the forces inside.
Tip: Be careful standing up and using your binoculars to tag people. They can see you if they get too close and happen to be facing your direction.
Take a look to the north and you will see some cement steps. If you wait long enough, you'll see a guard who patrols into the first room on the right, eventually doing a full lap through all the rooms on both the right and left side of the alley.
When the coast is clear, sneak down from your perch and head for the stairs. Hide behind some boxes below the stairs, then wait for the guard to enter the room on the right. When he does, sneak up the stairs and go in the first door on your left. Head north into the next room and wait around the corner. When the guard passes by, sneak up behind him and put a knife in him.
Exit back into the alley, then go into the door in the northeast corner. This room will have two jail cells, a ladder going down a level and some stairs going up. You're going up the stairs, then through the next room and up another level to where you'll complete the objective, locate the informant's cell.
Tip: Be careful heading to the informant's cell. You could very well run into a guard or two along the way, but they should be isolated and fall victim to stealth takedowns.
Once you meet the informant, your objective will update to search the commanding officer. Staying on the level you are currently on and head outside to the roof. There will be two guards in this area. Sneak your way around and take them both out (quietly), then head back into the informant's room. You are going to head down two flights of stairs, then down the ladder in the room with the two empty jail cells.
You'll now find yourself in a tunnel on the ground level of the Fort. If you look outside of the tunnel, you'll see some spiral stairs in front of you. Before you head that way, be cautious of a patrolling guard. If you want, take him out, or simply just sneak past him. Continue to be careful, though. You'll find another guard at the bottom of the stairs, one on the wall halfway up and another at the top. If you're careful and aware, you should be able to sneak to the top of the stairs, turning right and hiding in a room.
From this room, look out and see a guard on the catwalk in front of you. You should have no trouble taking him out with a bullet from your Welrod. Cross the catwalk, go down the stairs and take your first door on the right. This will be the room with the officer in it. Sneak up behind him and use a stealth takedown, then search his body to complete your objective, search the commanding officer.
With this key in your hand, you're going to head all the way back in the direction you came from. Retrace your steps, being very careful of any guards that you've left alive and sneak back into the tunnel. Climb the ladder, then the two flights of stairs to end up at the informant's cell. This will complete the objective to free the informant, but also give you a new one requiring you to clear the courtyard.
If you have them, it's time to lay some traps to make sure that your position is protected and none of the remaining guards gets the drop on you. If you have one, lay a Trip Mine at the top of the stairs in the same room as the informant. Next, go outside and to the southeast corner of the roof. Once you find a set of stairs, lay another Trip Mine. Now go to the west side of the roof where you'll find a ladder. If you have a Trip Mine, lay one more. If not, you can use an S-Mine or Land Mine in its place. This will cover the only three points of attack for the position you're about to take.
From the ladder on the roof's west side, look to the southwest and near the front gate of the fort. It will now be crawling with bad guys. The good news is that there are plenty of trucks and explosives nearby that you can use for multi-kills. That's right, you're going loud now. The game left you plenty of Panzerschreck rockets, so why not put them to use? Before you do, however, use your binoculars to tag all of the soldiers below, as well as take note of some of the explosives in the area that you can use to take out multiple enemy soldiers in one shot.
Things are about to get messy, and anyone you didn't kill before will most likely come after you now. Good thing you laid those traps, huh? You should be safe from your position, so use all of the Panzerschreck rockets going after multi-kills and taking out the bulk of the forces. When you're done with that, use your sniper rifle to pick off the rest. If one of your traps goes off, replace it with whatever you have remaining.
When everyone is dead, you'll have completed the clear the courtyard objective and received a new one, head to the battlements. Pick up any of your traps that haven't been detonated, then head down to the ground level and over to the front gate of the fort. Climb the ladder indicated and take up a position on the wall to cover the informant.
Your new objective is to provide covering fire from the battlements. Head all the way to the end of the wall where there's a wooden platform. From here, you will have all of your shots masked, so just start picking off anyone and everyone you see. Sometimes the bad guys are hard to spot, so pay close attention to where gunfire originates from and keep scanning all the bushes. If the informant isn't moving forward, scan the area until you find what's holding him up.
Tip: We found that when the informant wouldn't move, blowing up the trucks in the area was actually quite helpful. Two shots to the vulnerable points on the front should do it. If you're not sure where they are, look through your binoculars and they will be highlighted red.
Once the informant escapes the fort, you'll complete the mission and unlock No Refuge, a trophy and achievement for finishing Mission 4: Fort Rifugio.