Fog of War Achievement/Trophy GuideIn Mission 7 '
Death Factory' you will be caught in an explosion and come across a
guy hanging dead from a parachute, this is the start point. You will be attacked by a
dog which
doesn't affect the achievement in anyway as it will always see you but after killing it you need to
hug the right side. Follow the path and you will see a
flamethrower guy killing your people so drop down and
kill the enemy in-front of you then the one
around the corner who may turn around if you are to slow so make sure to kill him
quickly if he spots you! Now kill the next guard that is by the building to the right and once you and your buddy go through the door you will earn this.
You can restart the checkpoint if you get spotted.Here is a video guide: