In Mission 7: Death Factory, you must get through the foggy forest without being detected by human enemies to get the "Fog Of War" achievement. There is one dog that will always detect you, which is fine. It is the woods area where you see the dead pilot hanging from his parachute. In the first section, after killing the dog, stay to the far right side of the area. There are only three enemies and they are easy to move past if you wait behind a tree until they are gone. You will then reach a larger section with a flamethrower enemy. Stay to the far right side of the area. There are two enemies patrolling, but you can kill them with melee attacks. Stay to the right side and melee kill the enemy in front of the bunker while the other enemies are walking away. Your teammate will kill the second enemy in front of the bunker. You will get the achievement after reuniting with your teammate, opening the door inside the bunker, and reaching the woods area that does not contain any fog. Restart from the checkpoint if you get detected. If an enemy sees you for just a moment, it is fine as long as you do not alert the entire camp.