Spec Ops: The Line - Chapter 9: The Road

Before using the ropes to descend, turn around and look just to the right of the door. You'll see an American Flag draped on the wall. Grab that, it's a piece of intel. Use the ropes to rappel down the building and into a lobby. Walk outside and you'll come to another of those choices. You'll have to shoot one or the other of the two men. There's no way around this. If you try to just walk away, you'll die. If you kill the soldier, you'll get

*Achievement: Damned If You Do
and if you kill the civilian, you'll get
*Achievement: Damned If You Don't

After you choose, run forward over the dune. When you get to the other side, sprint straight down the dune and take cover on the left side. You'll be attacked by quite a few enemies straight up the middle but there will also be enemies up on the train tracks and on the large dune to the right. Use Lugo to take out these particular targets while you clear the others. Just keep fighting from this position until the sand storm comes.

When the sand storm hits, you won't be able to give commands and you'll have a hard time throwing grenades. Keep your eyes open. Move up the middle and you'll see an APC on the right side. Just past the APC will be a couple of enemies in the middle of the path. Kill them and then go past the APC. Turn back to face the tail end of the APC to find a single enemy. Kill him and continue through the sand storm. A little further ahead, you'll run into a similar group. Kill them too and the path will turn right. Run up and take cover in the bus.

Just on the other side of the bus will be two enemies, one of which will be trying to light a flare. Kill them both but only move up a little ways as two more enemies will approach by vaulting over the cover on the right. Kill them and then go straight ahead. You'll take shelter inside of a rather large pipe.