aka Apokalypse now-run.
Kill the 4 dummy-enemies at the beginning of the game to get full perks & proceed to the Camp.
Mark everyone in the camp and wait until the guy on the left dragged the body for a few seconds. Send one strike in the middle of the first group and immediately another on at the 3 guys on top. Pick up an AK and proceed until you get to the River.
By following the River you will eventually get to the objective with running into almost no enemies/troubles. Should someone spot you just sprintslide and stay down for a few seconds.
Your only detour should be to rescue Pvt. Walter(?). He's in the Ghost Village Camp behind the Napalm fields. If you hug the right side while approaching the camp you can drop down into the house where he is being held. Talk to him, walk a few meter out of the room until your character starts talking and "Mission completed" shows up. Go to your roster and unassign him and immediately leave the area WITHOUT getting spotted. Keep hugging the right side and you should be in the clear. He shouldn't die this way and despawns after a few 100ms.
Once you reach the final area hug the left side and kill the guy at the mortar with a throwing-knife and make sure to stay undetected otherwise the enemies will wreck you. Don't worry, if they do there's a checkpoint once you get to the area.
Pick up the C4 and plant it at the AA-Gun but DON'T detonate it just yet. Use the mortar to destroy the other AA-Gun, get up and back away a few meter from the C4 and destroy the 2nd AA-Gun.
You now have infinite Airstrikes availaible. Use them to kill the remaining enemies and call Walter before picking up the documents. As soon as you did, get down in the trench-rooms and use airstrikes to get rid of the enemy-groups. Save the Ak-Ammo to get rid of the helis by shooting the pilots.
All in all 2/10 difficulty.