The mission follows the path taken in the single-player chapter "The Monastery." Although the mission follows the same path, a short segment has been cut from the end to make the co-op mission end in the courtyard, whereas the single-player chapter ends shortly after the courtyard fight.
In the following walkthrough, the bold letters in brackets refer to the locations marked with letters in the accompanying images.
Start of Mission
At the start of the mission, all players will spawn together a short distance from the monastery entrance, at the bottom of a flight of stone stairs. This effectively serves as a checkpoint, as if all three players die, they will respawn here.
Make your way up the stairs, and at the top, you'll come to a broken bridge. Across this bridge are two soldiers, who can be easily taken out [A]. Up to the left you'll see another soldier on a wooden balcony [B]. Following this, you'll face several soldiers who pour out of the building in the courtyard. During this fight, several more soldiers will climb up the cliff face [C]. On Hard and Crushing difficulties, all of these soldiers will be either Dragan or Zorskel. A good tactic is to hang off the edge of the cliff and pull them off as they reach the top.
Once all these soldiers have been defeated, a drawbridge will open, and you can proceed across the water. Here, you will again face several soldiers. Killing them all will activate a checkpoint.
You will be informed that a checkpoint has been reached. After this, all players will be required to stand in individual red circles to advance the mission. Before doing this, look around the map for weapons and ammo. After all players enter their circle and press the mission will progress. You will be given a new objective: find an RPG-7 to blow the door open.
Soldiers will begin to swarm into the courtyard that you had previously cleared. Fortunately, they can not cross the drawbridge [A] which makes this section slightly easier. The more heavily armored soldiers (such as Dragan and Zorskel) tend to gather around the drawbridge [A], while the other weaker soldiers keep around the building to the right [B]. Within this group of weaker soldiers will be several Sarks, armed with RPG-7s. Once the soldiers have been killed, take an RPG and blow open the door. This will activate the next checkpoint.
Take this time to get what ammo you can. At least one member of the team should get what explosives they can (i.e. grenades and RPG-7s). Following this, all players must enter their individual circles and press to proceed. You will proceed through the blasted out door and find yourselves on a ledge. You will immediately be under fire from between one to two Heavy Weapons Troops (depending on difficulty setting), located at [A]. The player with the explosives should focus on taking these out. There are a few guns scattered on the ledge that they can use when their explosive ammo runs out. There is a Dragon Sniper hidden around to the right hand side of the ledge. Apart from the heavy weapons troop(s), several soldiers will emerge from the doorway [B] and proceed down the stairs, until they reach platform [C]. After killing these soldiers, you can proceed up the stairs (be wary as Dragan soldiers can emerge from [B] as you move up the stairs.
Head up to point [A], and take whatever ammo you need. only one of your team should proceed up the wall, as more soldiers will appear on platform [C] as they climb. These soldiers have sniper's rifles, and will attempt to kill you from down there. The others will slowly make their way up to you along the stairs if you do not kill them first. After they are all dead, again send only one team member up the tower. When they reach the interior of the tower, a second wave of soldiers will appear. You must now defeat this second wave, before climbing the tower. Once inside, you will have to kill a few more soldiers as you make your way down to the bottom. When you reach the bottom and have killed all of the enemy soldiers, you will activate a checkpoint.