Start out on the flak gun and concentrate your fire on the bombers. They always attack from the same directions in the same order, so if your radio towers get blown up, just replay and you'll have the jump on them. Taggert is kind of a wuss so it is possible that you'll die on the flak gun.
Once you shoot down two bombers, jump off the flak gun and head down the hill, killing anything in the way. Go around to the left when you get to the bottom and there will be a fence you can cut. Do so and kill the Nazis behind it. There are a lot of them in a small area and you should have some grenades so now is a good time to grind towards your grenade kills... Once they are all dead, enter the small courtyard and head over towards a locked door that you can pick. Pick it, call in the airstrike and then head back out to the friendly tank at the bottom of the hill, which will blow up. Shoot a few more Nazis and then run to the star to end the level.