I'm saying that Iwo was unique because it was a hopeless death trap. The Japanese had worked for many months to make it as efficient as possible and those who survived the first weeks knew that they had to back into that mill and almost certainly get killed our mutilated to gain the next objective.
If you haven't understood my point so far, you never will.
Never having served in combat...or near it...I can't speak from personal experience.However,a quote comes to mind regarding bravery in combat.IIRC an Admiral,or Marine General,in assessing the performance of the Marines during one the Pacific battles of WWII (can't recall which one) said something like "in this battle uncommon courage was a common commodity".
IMO...the Army,Navy,Air Force *and * Marine Corps fought skillfully and courageously in WWI,WWII,Korea,Vietnam and the Middle East.