Decisive battle was only one part of Japanese planning

If Japanese planning revolved around the decisive-battle concept, why was the navy still unprepared for the wider war?

The decisive-battle concept was only one part of Japanese planning; realists within the service understood the wider danger, so its lack of preparation had deeper causes.

Japan's naval plans did not revolve exclusively around one decisive fleet engagement. The decisive-battle concept was only one part of its doctrine and operational planning. Many people inside the Japanese system were realists who understood the scale and character of the conflict they faced. Their presence makes the failure to prepare a more complex institutional problem than simple blindness to an extended war.