Kantai Kessen concentrated Japan's total fleet against an enemy detachment large enough for its loss to change the balance. It was not enough to defeat a trivial scouting force; the target had to be a significant portion that could no longer mass against Japan. Geography constrained the idea because a long-range deployment of the main fleet might leave the home islands uncovered. The doctrine was an adaptable concentration principle for several possible wars rather than a single prewritten American scenario.
Chapter · 17:33-19:05
How Kantai Kessen was meant to work
The doctrine sought local superiority against a damaging portion of an enemy fleet, normally in waters close enough to avoid exposing Japan.