Call of Duty: Modern Warfare 2/Hidden

Walkthrough
Start off the mission by picking up he silenced Mini-Uzi, then walk forward and knife the guard.

Now crouch and move near the car, aim down your sniper sights and kill both the enemies in one shot, now continue forward but instead of going to the field, turn right and go forwards, there should be one enemy, knife them then take cover behind the cargo containers.

There will be a sniper hiding to the far right of the filed behind a cargo container, take him out then move right, looking to the left for an enemy, after you kill him, move up to the truck on the left and there should be a sniper behind it. Now check how many kills you have. There are 8 snipers in the field. (12 in total). Move up to the large amount of destroyed tanks, there will be two trees in front of you, a sniper will be near the tree closest to you, kill him. There will be one sniper on the other side of the destroyed tanks, if you can get a clear shot through then do this. There will be two on the higher ground above the large pile of destroyed tanks, kill these then run up to the single destroyed tank to the left, get out the mini Uzi and you will find the final sniper on the ground, find him and kill him, then continue on to the enemies coming down a road.

Try and get a triple-kill, then snipe the enemy in the church tower. There will now be three enemies in the graveyard, it is best to kill one and alert the other two, then run back to the start of the mission until they lose you and then pick them off one by one. Now go up to the church tower and kill the group of enemies, continue on to the house on the right killing the one in there and from here, shoot any enemies you can see, you will probably alert them, if you do, kill them all then continue on to the next house on the right.

There will be a lot of snipers in the field, work slowly and kill them all from the building, then go around to the left and continue checking for snipers as if you miss one, you will have to re-start the mission, two people help here as one can be used as bait. After all the enemies are dead, head to the finish.

Pro Tip: Before killing the snipers in the field, spare the lives of the two hostiles in the barn in front of the house. It will avoid elevating the alert status of the snipers in the field, and they'll be easier to pick off with the silenced rifle. When you kill four of the snipers, crouch walk towards the last sniper (whose line of fire is blocked by the building in the field) to the right of the two hostiles talking in the barn. They will not notice you. Go into the field building, plant claymores at each entrance, then toss satchel charges near the last sniper and set them off. When the last sniper is killed, head to the exfil point.