Afghanistan has the most. Once you parachute in, the back to back mode will contain at least 4, and possibly 5, 6 or 7. The first 2 come from your starting viewpoint, then turn around, take out the next 2 (try to do it fast to stop them blowing the other one up), and then watch the directions to get any more.
Once the back to back is over, 1 or 2 more may come from the direction of the 2nd lot from back to back (ie from the cave area).
Further on there are a few more inside the mission, specifically 2 who come out after you kill the mounted machine gun you need to Step Jump over the boxes to get behind.