"Contingency" is the first mission of Act III. You again assume the role of Gary "Roach" Sanderson accompanying Captin Price on a mission in Russia.
The beginning of the level is very simple, follow Price's orders. It was meant to be done stealthly, so take your time. Only kill when he instructs you. When you are tasked with taking out multiple enemies, take your time lining up the first shot. Make sure it will kill your target. Try to take out your next target as quickly as possible and always be ready to fire another shot or two incase you miss, or don't kill him immediately. If you ever shoot down an enemy and they begin standing up again, everyone will be alerted.
Side Note: This part is very similar to the Spec Ops mission "Evasion."
Soon you will be compromised by an enemy tank and forced to flee into the woods. Once Price informs you that it's safe, the sneaking continues. Avoid a couple patrols and eliminate a few more guards. Play it the same as the first bit.
Eventually, you will reach the top of a hill and Price will have a short conversation with our good friend, Soap McTavish. You'll also be granted the use of a predator missle. Unfortunately, upon the activation, it will be shot down by a mobile SAM site. As a result you'll have to fight with guns again.
Slide down the hill behind Price. New weapons are convieniently placed for you at the end. I chose the M240 Heartbeat and the P90 ACOG Sight. The choice is yours though. Also at this time, Ghost and other reinforcements will join you.
Once you've picked your new weapons, cross the road and take cover behind the parked tank. Look to the right, and mow down the rushing enemies. The M240 makes this very easy. Once the flood of enemies to the right stops, a couple will come from behind some trees over to the left. After clearing this section, move to the right and crouch next to the far side of the blue house.
Directly in front of you, enemies will be shooting at you from behind ammo crates. A few guys will come running from the left side as well. Be careful not to go past the corner of the blue house because a prone enemy will be on top of the red house to the left. After you've taken care of the enemies in front of you, it should be safe to peak around the corner and shoot the one on the roof.
Move up to the crates with your team but beware that two enemies will be at the bottom of a slope behind them, ready to kill you. Once everyone has been dealt with, follow your team along the path.
This next section is the only tough part of the mission. It's very reminiscent of "No Fighting in the War Room" from Call of Duty 4. On veteran you have two minutes to rush through packed enemy territory and reach the submarine. I'm sure there are a couple ways to complete it, but i'll describe the way I did it.
When you reach the ridge with a wooden fence, Soap will be communicating again and predator missles will be ready for use! Bring up the first predator missle and send it on the group of enemies in front of you, at the bottom of the ridge. Now the countdown begins. With this area clear, jump over the wooden fence. No need to follow the path all the way around.
If you chose the same weapons as me, it would be best to switch to your P90, for better mobility. You will run too slow with the M240.
Run forward through the chain link fence towards the building marked "33." An enemy will run through the door to open it. Sometimes you'll see him, sometimes you won't. Either way one will be waiting for you right inside the door. He might shoot you, or he might try to run away. Just be ready. Occassionally another enemy might be in the right corner of this room. Be prepared for him too. Now proceed through the door and aim down the doorway to the left. One or two enemies will be there. Take care of them. Don't go through this doorway just yet. At this time the rest of your team should just be coming through the entrance, they will take out the rest of the enemies around the corner. Take cover to the right side of the doorway and launch the second predator missle which should be online by now. Your only target for it is the enemy helicopter. You should also be informed that there are 90 seconds left.
Meet up with your team at the exit of the building and turn right. One or two more enemies might try to stop you here. Deal with them and head for the oil truck. Run to the left side of it and go prone. Wait for the two enemies to rush down the stairs off the helipad. Around this time another predator missle should be ready. Send it slightly northwest of your position. You should now recieve a 60 second warning.
Move under the roof and stay on the left. Your teammates will come up the right. Help them pick off the enemies on that side. Once they're gone, sprint forward to the cement wall that has a red truck parked by it. Get to the edge of it and kill the enemy to your right. Once you've regained your breath, dash forward to the right side of the shipment containers. Toss a flashbang down the middle of the two rows and another on the right side. Finally, sprint up the right side to your destination. Your team will move up with you. I made it with about 25 seconds to spare.
Your last objective requires you to defend the submarine. Kill the immediate infantry, then run up the staircase of the left building with Ghost. Go prone next to the two grey boxes in the back corner but make sure you're facing the stairs you just came up. Send a predator missle on the convoy that just rolled up. Now stay where you are and pick off the few enemies that make it up the stairs. Other than that Ghost will do most of the work. Continue holding out until Ghost and Price begin their conversation.
Side Note: If this is your first playthrough of the campaign you will also earn the "Desperate Times" achievement.