In ww2, Japan had both intelligence and courage.

Japan had the intelligence to develop the Zero, the best fighter plane in the world, for awhile. They had the intel to develop the Long Lance torpedo, tyhe best torpedo in the world, for awhile, highly-respected throughout the war. They had the courage to win a great number of battles during the war, often against greater forces.

So, what happened? First & foremost, Japan couldn't begin to match the war material production of the USA & her allies. Then, as Prince Hagashikuni, the Emperor's great-uncle said, "Japan had both courage and intelligence, but couldn't use them together."
Most of the Japanese officers were Samurai, following various branches of Bushido, "the Way of the Warrior". this led to many unnecessary deaths of able commanders in all service branches. For example, at Midway, Adm. Tamon Yamaguchi, second-in-command of the carrier force, went down with the carrier Hiryu, blaming himself for the loss of the four carriers, although he gave no operational commands, etc. Yamaguchi was a very-able commander, dubbed as yamamoto's successor if needed.More than once, Japan could've used his services in later naval actions.

There was Lieut. Joichi Tomonaga, a rising Naval aviator, who replaced the ill Lt. Com. Fuchida as leader of the Midway. He was a very able Naval aviator leader. His plane was hit at Midway, & couldn't hold too much fuel, & couldn't be repaired aboard a carrier, but he absolutely refused to either use another plane or sit out the mission against the Youktown, even though he knew it'd be a one-way trip. (It became moot, as, while attacking the Yorktown, his plane was shot up by Cmdr. Jimmy Thach, & exploded.) Point is, Tomonaga wouldn't have survived anyway.
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