I'm a bit of an amateur historian on the Pacific war and knew very little about this campaign before the series - after wards I did more reading and was surprised to learn that that battle was THE most costly of the entire war for us in terms of square miles involved.
Even in my USMC history classes in boot camp, they glossed over Peleliu really quick and went straight on into Guadalcanal, Tarawa, and Iwo Jima.