Due to lack of money, better forget about buying new equipment (unless you're trying to collect all the masks). You start this mission on a parachute. To get some extra cash, use a sniper rifle to shoot the rear rotor of the starting helicopter. This should put his on the ground forever. This will surely attract guards' attention, so shoot them too.
When you land, the third back-to-back action will start automatically. The biggest problem here are Martyrs - suicide enemies with bombs attached to their chests. You should have the whole area under control and kill these guys before they get close.
After this maneuver, a few additional enemies will appear. Of course you must shoot them all. During that gunfight you may use a nice vantage point placed on top of a container; your buddy must help you perform a step jump in order to get up there. Finish everyone and move to a mining cave.
Move forward, through the whole cave. On the other side you'll find some sandbags. Hide behind them.
There'll be a manned turret to your right. Let your buddy collect all the Aggro (or do it yourself) and finish that enemy in cooperation. The rest of opposing force is located in front of you (watching from position of a player walking out of the cave mentioned above). Finish them with traditional methods - in a gunfight. Using Aggro and surrounding can be a bit difficult here. Move forward or approach the turret (watch out for proximity mines). You'll have to finish some additional guys. Do that and get close to the first M-11 missile. Place an explosive charge in the designated place and hide somewhere. After the explosion return to the route filled with sandbags, where you were struggling a pack of enemies. Follow that way - you should see another cave. Enter it.
You'll see a gate inside, on your left hand side. Get close to it and press [A] to rip it off with help of your buddy. You'll find a place suitable for a step jump. Perform it and pull your partner up. Move forward, exterminating every single enemy. In the end, you'll reach a large area with another turret and a few unfriendly Afghans. Kill them all (note there's a vantage point on a container) and move forward. There's a ledge near the tents - it leads to another location.
There's a parachute waiting for you. The characters will use it automatically and you'll have to steer it using left analog stick. Beware of hitting the rock walls and try to avoid bullets and missiles shot at you. If you hit a wall, your flight will get some acceleration. Land in the enemy base. Once the heroes reach the soil, a back-to-back maneuver will start automatically - shoot all incoming enemies. After that, you'll be able to enter the complex through the main gate.
Now it's time for a shopping spree. Buy some new stuff if you'd like to have something new and you can afford it. After the shopping, the gate in front of you will open and a bunch of enemy soldier will open fire at you. There's a lot of opponents here and the time is extremely limited, so let your buddy collect the whole Aggro and take the stairs on the right (watching from the place you do the shopping) to approach the missile.
Plant the bomb and get back. Heal your partner if he needs help. Now go left, watching from the shopping position.
A few enemies will get in your way. Finish them and move forward, passing a truck. There are stairs among the rocks, that lead to a system of steel footbridges. Go upstairs and watch the cut-scene presenting a well-armored terrorist entering the area. Take another stairs to get close to your tough enemy (beware of mines! Try to shoot them when opponents are standing near them).
Approach the gate used by heavily armored guy and press the button located next to it. The gate will open - get inside and press another button. You should find an elevator - use it to continue the game.
Get out of the elevator and take the riot shield leaning against the wall. Take the left way and let your buddy eliminate all visible enemies.
You should approach another gate with buttons. Use them and enter the next location. You'll meet another group of enemies inside. Shoot them from behind a cover. Move forward and take another riot shield with you.
Proceed and kill all enemies attacking you and your buddy. Take the stairs to your right and go to the lower level of the complex. There's one additional guy there. Take him out and enter the corridor. Move forward and finish all incoming enemy forces. Get upstairs and face another group of Afghans. Look around - you should notice a gate marked with a Russian sign and number three. Go that way.
You'll find Hicks there - he has been a collateral for some time. Open the gate and him with you. Now you must get back to the previous location. Order your buddy to lead the way and kill all incoming forces. If you notice he won't handle the job, put Hicks down and help him with your primary weapon. Move forward and get to another elevator located in this mission. Leave Hicks near it and call the elevator.
Once it takes you to the lower level, you'll have another occasion to buy something. If you're loaded, get yourself a sniper rifle - it'll be quite useful in the final part of the mission. After the shopping, move forward. You'll approach a large area filled with enemies. Take the right passage and run to the manned turret you'll see. Surround it and finish the gunner. You can now use the turret to kill more opponents. However, if they're not in your field of fire, abandon the turret and use the sniper rifle. After the gunfight you can complete a secondary objective, which is using the laptop located near the centre of the whole area.
Now go upstairs to another set of footbridges, placed above the location in which you were struggling Afghans a second ago. Finish remaining enemy forces to turn on another cut-scene.
It will show another tough guy - Al Habiib. You have to kill him and his personal guards. Habiib and one of his men are well-armored, so you need to approach them silently from behind. Order your buddy to keep position and fire at the enemies, while you sneak up on Habiib's bodyguard and kill him. The rest of your target's guards are easier - use the sniper rifle to finish them.
When Habiib will realize his men are losing the gunfight, he'll retreat and hide behind a cover made of steel. You can either kill him with grenades, or shooting the top of his head, visible for you from time to time. You choose the way.
Make sure every single enemy is dead and open the door located behind Habiib's hiding place. Inside, you'll find a place marked in red. Place an explosive charge there and get out there.
Mission in Afghanistan ends right here.