Japanese planning did not expect a long shipping war

Why did Japan put less emphasis on motor shipping and escorts?

Its planning drew on shorter-war experience and did not anticipate the scale of a long Pacific logistics conflict.

Japanese preparation reflected previous wars and a belief that the next conflict would not become a prolonged struggle of merchant shipping and escorts. Japan's reference points included the Russo-Japanese War, the limited Far Eastern fighting of the First World War, and naval assistance in the Mediterranean. None reproduced the scale or duration of an industrial trans-Pacific shipping war. Real combat experience can still mislead planners when the next war demands a different kind of endurance.