Reply #10: It wasn't intended to be comprehensive

[Seneca]

It's just such a far-reaching theater, with so many angles from which to choose. So Spielberg and Hanks narrowed it down by basing it on three separate marine memoirs, including the diary of John Basilone. In fact, if not for Basilone's story, Iwo Jima wouldn't have been covered even as briefly as it was - because Spielberg mentioned that Clint Eastwood already gave Iwo Jima such excellent treatment in his two back-to-back films (which included the until-now-overlooked Japanese perspective), and therefore he didn't think it needed coverage beyond Basilone's death there.