When we look at the casualty figures for battles in the Pacific War such as Guadalcanal, Saipan and Okinawa, it is clear that the Japanese suffered disproportionately higher number of fatalities than the Americans did. I am aware that factors such as disparities in firepower, quality of equipment, the availability of artillery and air support (all in favour of the Americans) in addition to the Americans' numerical advantage played a major role in this. However, I would like more information and insights on Japanese infantry tactics, their flexibility in terms of decision-making in the heat of battle and the quality of leadership in the field when compared to American infantry. Can anyone with knowledge in this field provide more information?
Combat casualties in the ground forces were often similar in number (e.g., Guadalcanal, Peleliu, Okinawa). Since typically 3/4 to 4/5 of the US casualties were wounded, and almost all of the Japanese combat casualties were killed, Japanese fatalities were higher.
Why were there so few surviving Japanese wounded? In the island battles, the Japanese were usually unable to withdraw wounded (or sick) soldiers from the island, or even from front line positions. When able to, wounded (and sick) soldiers would continue to fight, sometimes taking part in suicidal banzai attacks. To avoid capture, wounded soldiers would often commit suicide (including requested assisted suicide), or their fellow soldiers would kill them to avoid their capture, if they were unwilling or unable to commit suicide or assisted suicide.
Similarly, able-bodied soldiers, at or past the point when units in other armies would usually surrender would make suicidal banzai attacks, or simply commit suicide.
Tactically, two things strongly contributed to higher Japanese deaths. First, the Japanese were often defending a series of static positions. This allowed US forces (and other Allied forces) to concentrate on each Japanese strongpoint in turn, giving the US forces overwhelming local superiority. This was not always easy, since Japanese defensive positions were sited for mutual support. Still, the outcome was usually that each Japanese position would be destroyed, with all or most of the Japanese soldiers killed. Second, on occasion, the Japanese would persistently attack strongly defended positions (e.g., the Japanese attacks 24-26th October during the Battle of Guadalcanal), and would usually suffer disproportionate casualties (e.g., in the just-mentioned attacks on Guadalcanal, about 8 times the total casualties and about 30 times the deaths).
Further Japanese deaths came from starvation and disease. US forces also suffered many disease deaths, but with a more effective and better supplied medical system, proportionally far fewer. For example, at Guadalcanal, US ground forces combat casualties were approximately 6,000 (1,600 killed), and Japanese combat casualties were approximately 8,500. The Japanese attacks on 24-26th October largely account for the different in total combat casualties. The Japanese suffered over 10,000 disease and starvation deaths. US disease casualties were about 5 times greater than US combat casualties (and disease deaths were many, but far fewer than for the Japanese).
In the Battle of Buna-Gona (the fighting for Buna, Gona, and Sanananda in New Guinea, November 1942 to January 1943), US and Australian combat casualties probably exceeded the Japanese combat casualties (about 6,000 (about 3,500 Australian and 2,500 US casualties, under 1,000 total KIA) vs about 5,000-5,500 Japanese casualties). Unusually, about 1,200 Japanese wounded survived the battle, having been evacuated. Allied hospital admissions due to disease were 4.8 times greater than the number of wounder, and the disease rate was higher still, with sick men still capable of fighting often staying at the front lines. Adding another 3,000 disease and starvation deaths to the Japanese total, the number of Japanese deaths was much higher than the Allied total, despite higher Allied combat casualties.
Combat casualties on Saipan were significantly lop-sided, with about 24,000 Japanese casualties vs 14,000 US casualties for the ground forces. As usual, the Japanese combat casualties were overwhelmingly KIA. Contributing to the disproportion was the war's largest banzai attack, with about 4,000 Japanese soldiers (and also some civilians) taking part. US casualties were over a thousand (as usual, mostly wounded) and Japanese KIA exceeded 4,000 (counting civilians). Japanese counter-attacks on the first few nights of the battle also resulted in disproportionate casualties.
In summary, combat casualties were often similar, but Japanese determination to defend positions to the death often resulted in just that: the death of the defenders, and Japanese combat casualties were mostly KIA rather than wounded. Japanese counter-attacks and banzai attacks increased Japanese combat casualties, with usually far fewer US (or Allied) casualties. Finally, disease, starvation, and suicide increased the number of Japanese dead.