Drop down and get ready for things to really heat up. Switch to the assault rifle and take up a position watching the breach point. There's a spot behind some ammo crates and next to a barrel. This gives you good cover on both sides. If you hurry, you can make it there just as they breach. Pour into them as they come through the door. You can turn on your nightvision goggles, but I found it easier to keep the goggles off and just aim at the red laser sights. If you fire wildly into the doorway, you should thin out most of the breaching force. Then kill off the rest of them to wrap it up. Go on up and out to the outer balcony.

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Switch out the assault rifle for the riot shield. Move up in front of Price and keep facing the marker. Strafe along the cliffside and cross out onto the bridge thing. This should trigger Price to take out the first guy across from you. Wait by the stairs and he'll fire on the next 3 that try to rush you. Switch out your shield for one of their assault rifles, and get ready to hit the next room.
If you can, throw a grenade at the spot right below where the men are rappelling into the room. You should be able to take out most of the assault troops with this trick. Then you just have to shoot the stragglers in the hand to get them to drop the shield and open themselves up. If not, then engage them briefly and cut over to the left.
Go up the path and shoot any of the advance guards that might be moving into the area. Then cut back to the right to flank all the guards and get around their riot shields. Move further into the tunnel with Price and take cover behind the ammo crates. Look over to the left and pick off the guards rappelling into the area. Just hold out for a bit until they fall back and dig into the exit. They'll pop smoke too. Go ahead and grab the thermal scoped weapon if you want, but we're going around it all.