More submarines could strengthen Japan's defence perimeter

How could Japan have changed its defensive perimeter or strategy to make it more effective?

Build more submarines.

Japan's defensive perimeter needed more submarines to become more effective. The answer repeats that recommendation without adding a deployment scheme or target list. Its value lies in the force-structure priority rather than an operational plan. A later exchange at 2:07:40 explains the industrial problem behind the shortfall: submarine battery production consumed scarce resources.