So you are on the beach, looking up that cliff. Looks hard, doesn't it? Well, it isn't.
Step1: Get a halfway decent squad. This one is important.
Step2: Go to one of the beached, unenterable boats to get a hook kit. I take the one with the shotgun because it elevates your badass factor by 50%.
Step3: Go to this place directly below the evil German bunker.
Step4: Throw the hook, and throw it high. If it looks like this, you're good to go.
Step5: Climb up until you reach this place. The Squadleader stays here, to provide a constant supply of troops. He may also watch the grenades that fly over his head and hit the beach.
Step6: The assault troops keep climbing until they reach this position. From here you have the perfect staging area to launch assaults on the bunker (use smoke nades for cover and the flamethrower for added awesomeness)
Another imaginary German bites the dust.