Call of Duty 4 Walkthrough - The Hunted/Death From Above
Bad news. The chopper carrying you, the informat, and your allies crashed. You'll have to go on foot through enemy territory. If it's not one thing, it's another, right?
When the mission starts head over the downed chopped and take whichever weapons you'd like. Stay as silent as possible as you make your way to the farm and ambush the enemies. On your way to the next farm, you'll have to crouch to stay hidden from the helicopter. Once the basement door on the next house opens up, head inside and take everyone out. Mid-way through the house, enemies will flashbang you, so be ready.
After you exit the house, you'll be attacked by dogs. Obviously, try to pick them off before they reach you. Automatic weapons work best, as you can just spray in their general direction. It's also good to keep behind cover, so you don't get shot while you're dealing with them. If they jump on you, smash that melee button like there's no tomorrow.
In the next field, you can use stealth, but with so little cover it probably won't last long. Stay behind the team, shadow their movements, and quickly snipe any enemies that spot you. It's possible to make it to the end without being spotted, but it's not easy.
Once the alarm is raised, prepare for a big fight. You also have the helicopter firing at you. You can take out the gunner by shooting into the gunner port. But the chopper is the least of your worries. Making your way through th greenhouses is difficult due to the sheer number of enemies. There will also be enemies hidden in the grass, so keep an eye down low and fire into any suspicious looking foliage. There's plenty of cover here, so take your time.
Once you're through all of that, you need to get rid of the chopper for good, and there's a stinger in the barn that will do just that. Remember that you need to line up your target long enough for it to lock on, and then fire.
The exit will be blocked by enemy troops and armor, but if you wait, air support will take them out and clear the way for you.