Ditto on Silent Victory. Required reading in my opinion... There were sub nets and minefields from the beginning, just not that many. It was one of those "what do we want to spend our money on most?" situations. ie, did they want to build ships, or put out defensive barriers? The thought process usually devolved into "a good offense is a good defence", so the attacks kept coming. Also, with the more than lackluster effectiveness of the US torpedoes, the feelings in the higher levels of command were "why bother?". So in some areas, they were rather late getting some harbors protected, especially the "conquered" territories, other than maybe Rabaul, Manila or Singapore and the like. Once the US had Saipan and Guam, the B-29s actually put out more harbor mines for the Japanese, some of course landed on shore, but they still lost a LOT of Japanese vessels lost to mines inside of, and just outside of their own harbors. There is minimal information on what the Japanese had actually put in place at most harbors, which the lack of information is most probably to do with the destruction of documentation just prior to the end of the war. We've not been able to find much in this regard, though I have seen some drawings (that I can no longer find) on US navigation maps, with the use of red pencil, de-marking where minefields were or were suspected to be. That is the kind of stuff that would be really cool to have on your NavMap in the game...
