I Am Your Shield Achievement
I Am Your Shield5
Keep the Elephant 100% intact in Operation A, Mission 3
This achievement is easier than it sounds. The Warthog turret doesn't overheat so you can just mow down all enemy forces. Watch your radar for any enemies, you shouldn't have any trouble keeping them away from your Elephant.
The only thing to watch out for, at least in my gameplay of the level, is at one point a Grunt hides in a door way near the top of your screen, avoiding your fire. Once you move slightly past the door way the grunt will come out, thinking he's outsmarted you. Let loose turret fire and show him who's boss! Shortly thereafter the mission will end netting you this achievement.