MISSION 13 - Three's Company
Mission area: Cauda
Note: Make sure you take a powerful primary weapon with a lot of ammo (such as an LMG) as it will be extremely helpful in the final section of the level.
Looks like Mario's on the mend, but it's time to go and raid the manufacturing plant that made the parts for the Bavarium tank. Jump in the sea chopper in front of Rico after the scene ends to get to the meeting point quickly. After your jaunt through the skies, you should arrive in the marked town. Grapple up the stone tower to the top to find a waiting weapon drop with a sniper rifle inside. Grab it and be prepared to use it as you are going to be fighting at long range for most of this mission.
After you're locked and loaded and the distraction is triggered, get ready to get to work. Your first enemy vehicle will circle around the outside of town before reaching the gas station. To take down cars effectively with the sniper rifle you can either aim for their tires, or the driver, or hit the vehicle enough times (but that does waste ammo, and you only have a certain amount). Use this initial single enemy as a warm-up to get used to the aiming and firing rate of the sniper rifle.
Then a swarm of military vehicles will start coming in from multiple directions. Use the markers to quickly locate and dispatch them, trying to make sure that none of them reach the gas station. When they arrive, the enemies inside will start firing on your allies, dealing damage to their health bars. If they empty, the mission fails. If too many reach the gas station or you run out of sniper ammo, you are better off grappling down and joining the fray directly.
After dispatching enough enemies, your allies will be on the move. You'll have to grapple and chute your way along the cliffs and over a few hills to reach the next meeting point. When you reach the ruined house acting as an overlook, reload your weapon from the drop and get ready for your second sniper session. Your two mercenary allies should arrive at the gates of the refinery below shortly. When they say, shoot the barrier gate at the entrance of the facility. This time you'll be protecting the duo as they move through the refinery. This means taking out the waves of soldiers and snipers that spawn and attack their position.
Be prepared to take down a decent amount of enemies. Quickly find each marked group and gun them down. Those who aren't good with a sniper rifle will likely run out of ammo and have to resort to escorting them through the complex in person on foot. When they reach the end of their path, they will leave the refinery in a helicopter and tell you to grapple onto it. This leaves you upside down beneath the chopper. Your escaping chopper will be attacked by gunboats, helicopters and fly over bases which will fire up at it, so it's your job to keep the helicopter alive by neutralizing enemy threats quickly. Your LMG should help you here, allowing you to take down helicopters fairly effectively. I would advise that for the last group you drop down and take out all the soldiers on the ground as your helicopter will hover in place until they are gone. When the landing zone is cleared, the mission is complete.