Move on up to the next slope and pull out the predator drone controls. This is pretty short lived though. Drop down and get to the little armory by the ammo crates. Go ahead and swap out the pistol for a shotgun or a sub-machine gun.

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Get up to the site of the destroyed SAM. Look forward and engage the men behind the sandbags. Just snipe them. Make sure that one of them doesn't slip down to the left of you. Move forward to the side of the house with Price. Stay here and soften up the Russians as best as you can. Then go up to the green house. This spot will protect you against the guards ahead and let you work on the Russians moving up. Also focus on the guards moving across the low rooftop to flank you.
Move out and use the sniper rifle to wear away the men at the back. Once you manage to clear a path, you can go down the road and finally make it to the submarine base. Use the second predator drone to blow up the helicopter on the roof. If you shoot quickly, you'll take out the vehicles too. Move into the base and fire on the soldiers in your way, but listen carefully for Soap. He'll report in when another missile is ready. One should be ready to go as you enter the base, so get somewhere safe and fire a missile at a cluster of soldiers. There should be one by the gas truck.
Keep pushing forward. Use the sniper rifle and the predator drone to clear out a path up to the fence. Go through and use the destroyed vehicles for cover. Save your predator missile and use it on the truck that should pull up in a minute. Fire on the next group and cross over the halfway point. Get through that little garage to get close to the submarine.
We have to hold the sub pen. Fire a missile right into the middle of the convoy that pushes up. That should kill the bulk of the first wave. The second one will probably come before your predator is ready again. Just fire it into the cluster as soon as possible. The third wave comes right down the docks next to the submarine. Fire on the soldiers and watch as the silos open and one big missile launches.