WWII and especially the pacific theater has fascinated me since my early teens. Everytime I watched a new documentary or read a new book on the topic I kept wondering how Americans seemed to have gotten through a battle with disproportionally lower casualties when compared to Japanese ones, especially in the island hopping campaigns. I understand that Japans Military leaders were often too stubborn to give up certain islands and demanded them to be defended to the last man and/or occasionally sent troops on suicide missions. When looking at statistics of the battle of okinawa for example, I do not understand how ~80 000 Japanese soldiers, who would rather die than surrender to the enemy were only able to kill ~15 000 American soldiers in the process of defending the island and ultimatly dying after having failed to do so. Wouldn't the fight-until-the-last-man menrality give the Japanese a psycological advantage over their counterparts? Or was the air and sea support too powerful for the Japanese to stand a fair chance against the Americans? As far as I understood the military technology of both sides was relatively on par at the time. How big of a role did the decryption of Japanese communication and over all American military tactics vs Japanese tactics play?
Tldr: What are the reasons for Japanese casualties to out-number American ones by often times 2:1 or more? (I.e. Battle of Okinawa 80 000 vs 15 000)
From US Marine vs Japanese Infantryman: Guadalcanal 1942-43 by Gordon L. Rottman (at least I believe that’s the book, 10% chance it’s another and I remember wrong), a good portion of it comes down to the hierarchy of command in the IJA.
You are correct that Japanese officers and commanders were frequently too stubborn to retreat or surrender an island. With that came extremely strict orders to their subordinates. Corporal punishment was a fairly common occurrence amongst the IJA for subordinates who disobeyed orders or tried to act individually. Because of that many IJA men were extremely hesitant if not outright fearful of acting on impulse or gut even in the heat of battle, waiting for orders from a CO for their next course of action. So in turn, with the loss of a CO a platoon of infantrymen or more could effectively be thrown into disarray, moreso than their American counterparts. Other examples would include if the crew of an entrenched machine gun or AT gun was lost, infantrymen would typically not attempt to replace it unless a CO directed them to.
Conversely, much of that was not present in US hierarchy. Obviously men listened to their CO but independence and free thinking was encouraged. If a CO was lost, men were encouraged to look to the next nearest CO if visible and mimic their movements. If not, then it was left to their gut judgement whether to retreat, push, or hold. With the IJA, they would typically continue on the last order of the CO unless another one directed otherwise.
This free thinking came as much of a shock to the Japanese, with the first few years of island combat leading the Japanese to believe the Americans had remote controlled mortars, machine guns, and AT guns due to the fact that if the operator of one of these weapons was incapacitated you could be sure that someone else would replace him, leading to the illusion of near constant fire from them.
So while the Japanese would frequently fight to the last man or at least extreme casualties, they would often inflict little effect on American forces comparatively who could react to changing battles and losses much more effectively than the extremely rigid IJA.
The book also highlights how much more common infighting was between officers and if an officer was lost and subsequently replaced, until proven in combat said officers subordinates would not respect their new officer. Other officers would not respect them either leading to a fractured fighting force with poor communication and coherence.
By late 1944-45 the IJN was a fractured shell of its former self. By December 1944 I don’t believe there was a single operational IJN aircraft carrier with most being sunk, in critical repairs, or unfinished. The IJN planes were thus almost non existent and the IJA and IJN had to share the limited airfield space on the limited few islands that could still support them.
So not only due to the US having near complete naval and air superiority of the entire region, they also could continuously cycle in and out new and fatigued troops, ammo, rations, medical supplies, equipment, and so on. Entrenched IJA men on an island like Okinawa had no such luxury, and also had no form of retreat, reinforcements, and didn’t believe in surrender.
Edit: typos