Why was the battle for Iwo Jima so important to America?

Extracts from a report comparing the Allied campaigns at Iwo Jima and Okinawa, June 1945

Catalogue ref: WO 208/1021

1. Comparison of Japanese Tactics on Okinawa and Iwo.

a. General

(1) A study of operational reports, captured documents, and PV interrogations discloses few basic variations between Japanese tactics on Iwo and on Okinawa. The few variances noted can be explained by the considerable difference in area between the two islands and by the smaller ratio of troops to area on Okinawa, rather than by any noteworthy development or change in Japanese tactics between the two campaigns.

(2) The ratio of Japanese to American casualties was considerably greater on Okinawa than on Iwo, but that is probably due largely to the more dispersed targets rather than to less effective tactics. The area of Okinawa is about 485 square miles, while that of Iwo is only about 6.5.

(2) The troops on both islands appear to have been mostly well trained. Army units which were better equipped than any Japanese troops so far encountered. The battlefield morale of the units on each island appears to have been high.

c. Casualties.

When the battle for Okinawa is completed, the total of Japanese dead and prisoners of war will be -- as on Iwo -- about equal to the total of the original garrison. On Iwo the ratio of Japanese to American casualties was about 1 to 1; on Okinawa it will be probably about 2-1/4-1. But the more favourable casualty ratio on Okinawa cannot be charged to deterioration in Japanese tactics. It seems likely that, despite a very considerable number of artillery pieces and heavy infantry weapons, the Japanese have not been able to place the same volume of fire on critical targets on Okinawa as on Iwo.