If you don’t have the crossbow by now, it’ll come in handy. Buy it and fully upgrade it. When you are forced to be stealthy, it comes in very, very handy.
This isn’t tough so long as you’re patient. Move to the embassy wall, be aware of the big lights and the cameras. Wait until the guard closest to you turns away, then climb the wall with the second set of windows, them climb over to the thrust on your side of the entry. When the guard below you is distracted, drop down and climb up the opposite thrust. After that, climb out on the windows on the far side in the dark. The next guard will turn away. Get to the far end of the building and climb the drain pipe. Follow the high path to the garage, climb down, and drop in when the camera is looking away.
Beyond the car is a guard and a camera. When the camera is rotated all the way to the right, it illuminates where you need to go. Wait until it turns away, then hop up and rappel down. After that, the general will send a guard away, and then stick close.
Now you’re weapons free! There are six guys to deal with. You can climb up to the balcony for an elevated position. Stealth is not an option, so you might as well be aggressive. After that, follow the marker up a set of stairs, patrolled by three guys, one on each level. At the top, you’ll meet a guard exiting the secure area. Use him to get through the door. You just need his body, he doesn’t have to be alive.
When you get off the elevator, you’ll need to take the first guy out to get through the RFID door. Stash him in the first corner inside the door. As Charlie told you, you can go through or you can do under. To go under, head up to your left. Watch your step and there will be no one to interfere with you. When you reach the far side, opposite where you entered, there is an office. There’s a Dead Drop in there, and a hole in the floor.
Turn the fans off, go around the corner, jump up to the pipe, drop down to the ladder. There are two guys above, shock or stun them if you want Ghost points. Use one of them to kill the lasers and access the terminal. Then you’ll have to sit tight for 90 seconds while the data runs. One guy will enter the computer room almost immediately, another will come in right at the end. Shoot your way through the heavy guy between you and your exit.
When you hit the ground, if you want to stay Ghosty, you may need to restart the checkpoint after the game saves. There are three guards who are coming into the room, one of which is armored. In the room behind them is one more guy. You can certainly take them out. But if you haul ass the second you start, you can run to the left corner of the room where there is a duct. They may hear you, but if you’re fast, they won’t see you.
Head through the vents, then onto the stairs. You’ll go down three layers, with a guy on each. Turn off the lights for more cover. Return to the vents and you’ll come out in a big open room. When the coast is clear, head down the center catwalk. Straight ahead of you is a room with a laptop in it, and beyond that is your marker. You’ll find one guard, and another RFID door.
When you get a chance to restock, consider heavy ordinance if you’re into fighting straight-on, because five guys, two of whom are heavy, are about to show up.After that, there’s 100 meters of open courtyard between you and exfiltration. There’s an HVT off to the left, three other sentries, and then more reinforcements including a dog and an armored guy. There’s plenty of cover for hiding if you want to try to slip away.
But wait, that’s not all! There’s another air cover minigame. And it’s rad.