I'm a civilian and my knowledge of military tactics is rather limited so please bear with me 
I watched "Saving Private Ryan" again a few days ago. One thing that made me wonder was the opening sequence in which the invading landing forces seemed to literally walk into unchallenged German defense positions (machine gun bunkers) and suffer severe losses. I realize this is a movie and I don't know how accurate and representative it is, although I'm sure military and historic advisors were involved.
So my perhaps naive question is: Why didn't the Allies take care of the bunkers via naval/aerial bombardment before landing the ground forces on the beach? According to this article, supporting fire by warships was provided. But the movie doesn't really reflect that. Is this simply a failure/omission on part of the film or were there any other reason?

I watched "Saving Private Ryan" again a few days ago. One thing that made me wonder was the opening sequence in which the invading landing forces seemed to literally walk into unchallenged German defense positions (machine gun bunkers) and suffer severe losses. I realize this is a movie and I don't know how accurate and representative it is, although I'm sure military and historic advisors were involved.
So my perhaps naive question is: Why didn't the Allies take care of the bunkers via naval/aerial bombardment before landing the ground forces on the beach? According to this article, supporting fire by warships was provided. But the movie doesn't really reflect that. Is this simply a failure/omission on part of the film or were there any other reason?