Move forward and enter the abandoned American base. Better find some cover, so the rebels who have taken this base won't be able to kill you. Shoot as many enemies as you can, including the one in a turret (use an Aggro tactic to do this). If your opponents are giving you a hard time, use the riot shield placed in the centre of the base. Get to the rooftop of the building located also in the centre. You'll find there the turret you were shooting at and Eisenhower, who must be evacuated.
When you'll meet him, enemy reinforcements will arrive. The turret is quite useless here, you must use your personal gun. Sitting next to Eisenhower and shooting at approaching Iraqis should do the job. When you kill everyone, a cut-scene will start. After it, you'll be able to continue the mission.
Move forward. Your next target is Ali Youssef's lieutenant. Go outside and turn right. Move into an abandoned bazaar, hide somewhere and shoot everyone you'll see. Moreover, beware of proximity mines - there's a couple of them in here. Proceed to a small building, killing and passing a guy in a turret. Clear the mentioned building and notice a gate and a wall located next to it. Let your buddy help you perform a step jump. Get to the higher level, finish visible enemies and pull up your partner, so you can both get on the other side of the wall.
Besides a group of regular enemies, once again you have unman a turret. Defeating these guys should be a trouble, but remember that you can get some extra cover by ripping door from a car nearby. Proceed to that turret and turn left. Move forward and enter a building standing on your way. Clear it and get on its other side. You'll find a bunker door. Open it with the button placed on the right side and get inside.
You'll find more Iraqis inside. A grenade or two should be pretty useful here. Once you clear the bunker, use the ladder to get to a higher level. Up there, you'll find another ladder. Use it, so you'll get on the bunker's rooftop. Now you have to eliminate the lieutenant. There's a helicopter with your target on board. It's about to start, so quickly use an automatic weapon to destroy the fuel container. The explosion should destroy the helicopter. Now turn on your GPS and look around to find a way to the ground. Follow the designated path. Run to a tunnel nearby and open door located in there.
Now you have an occasion to buy something. You'll have an occasion to perform a co-op snipe soon, so if you ran out of sniper ammo, get yourself something new. Move forward. Once you will notice enemy's base, you and your partner will be able to kill both guards simultaneously. Shoot them and attack the rest of the camp. Get to the turret and shoot at everyone coming to kill you, especially Martyrs. During that action, your buddy should get to the bunker nearby and mark it for aircraft.
Move further, but be aware of the fact, that someone may get to your turret and shoot you in the back. Notice that the area here is huge enough to use a sniper rifle. Use it to eliminate incoming enemies, including the one in another turret placed in this base. Pass the empty turret and move to the second part of the camp. You'll meet surprisingly light resistance here. Get to a small building and open its doors with the help of your buddy. A back-to-back action will start, so enjoy killing enemy Iraqis. When the maneuver ends, some opponents will still try to kill. Hide in the building you opened a minute ago - its windows are bulletproof. Eliminate resisting guys and enter the tunnel nearby. Open door inside to continue the mission.
Simply follow the road, killing everyone trying to kill you. Finish the guy in the turret and open the gate at the end of the asphalt road.
This is Youssef's main base. Turn left - it seems a good way leading to our target. Move forward, shoot everyone attacking you. You'll meet a well armored terrorist - use a grenade or an Aggro tactic. GPS will show that the way to Ali Youssef leads through a small bridge. Walk through it to trigger a cut-scene presenting your target and his very, very heavy gun as well.
Enter the warehouse in front of you. Kill the heavily armored guy inside and his buddies. Walk out on the other side of the building. You'll meet Youssef here - he's on a walkway leading to a helipad. If you have some sniper ammo, try to shoot him in the head. If you don't, do the same with standard ammo or throw grenades at him. Youssef will slowly fall back and stop near some fuel barrels. Note they're highly explosive :) His death should end this mission.