I love nothing more as Japan or America than seeing my opponent putting submarines in the water because I know I can manipulate the situation to give me the edge no matter what happens. You can’t block with submarines, so I can ignore any submarines you have and you cannot run submarines past my destroyers on picket duty, so I can block your fleet to my advantage.
As Japan if you spend enough time and $IPC to build an entire “picket line” of destroyers to counter a handful of US subs then the subs have done their job and the US has won that battle.
The point of the US throwing subs into the Pacific theater is not to take down the Japanese navy; it’s three things:
- force Japan’s ships into a defensive/consolidated posture which is less flexible on offense and more importantly slower to expand.
- force Japan to spend $IPC on something other than the land war in Asia
- do #1 and #2 as cheaply as possible and make it cost more for Japan than it costs the US