On the torpedo and bombing method the Japanese view:

" It was not before the fall that aerial torpedoing in shallow waters of only 10-odd meters was made possible with the great help of the technicians concerned, and it was also only in last August and September that the technique of horizontal bombing had been improved so that one hit might be expected from nine attacking bombers. "

From Isoroku Yamamoto´s letter to Admiral Takahashi 19 Dec 1941

From Pearl Harbor papers by Goldstein and Dillon

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