Killzone 3 Walkthrough - Six Months On: Part 4
5Full Walkthrough: http://www.gamefront.com/killzone-3-walkthrough/
Stick with the ISA trooper as he leads you along the ridge. You'll come out near some Helghast troopers out front of the ISA base. Kill them, then move in and start supporting your fellow ISA as they fight off the Helghast.
Run through the base and you'll find Narville before long. He's fighting a losing battle against the Helghast overrunning your position, and you get to help. Up front are a few machine gun nests you can use, but near the back up against some crates is a sniper rifle.
If you hit the objective button, you'll see the different entrances the Helghast are using to assault you. Try to keep them clear, or at least hide from their incoming fire. Keep dropping troops and eventually a troop carrier will enter the base. Kill it with a machine gun nest or that missile launcher you've been carrying for a while.
Take out a second troop carrier when it arrives, then just keep blasting away — watch out for flamethrower troops primarily. You'll need to move back toward the entrance of the area as the fight goes on, or you'll be killed. Eventually, a cutscene kicks in to end the chapter.
Full Walkthrough: http://www.gamefront.com/killzone-3-walkthrough/