What I am saying is that I feel a modification to submarine combat may be in order.
You may ENGAGE enemy submarines with attacking submarines, however if the defending submarines are UNDETECTED prior to opening fire (and I believe it goes Detection ==> Opening Fire ==> Attacker/Defender ==> Remove Casualties) then the defending submarines have the option to retreat BEFORE opening fire.
This would allow Japan or America to recover after a bad naval engagement because you would have to bring in destroyers to pin their submarines down and force them to stand and fight. Otherwise, Japan/USA could easily retreat and build more and keep doing that until they have the firepower to defend some surface ships.
Example:
Japan sinks the American fleet in Solomon Island’s Sea Zone 45 with 1 Aircraft Carrier, 3 Damaged Yamato Class Battleships, 2 Jet Fighters and 10 Super Submarines remaining.
America has nothing left, but America does have 56 IPC.
So America purchases 8 Submarines (Naval Industry would reduce the cost to 7 IPC putting America on even footing IPC wise with Japan’s Kaitens)
Japan attacks SZ 55
Detection Phase: No attacking or defending destroyers present, all submarines are undetected
Defending, Undetected Submarines decide to engage or withdraw
Attacker/Defender Opening Fire
.
.
.
The only change is that the defending submarines are allowed to chose to retreat before opening fire if they are undetected. This may make them harder to kill until you get a destroyer, but odds are, it will just force you too make sure you have a destroyer or two.