OpanaPointer wrote:One more point, that may have been brought up before. Territory of Hawaii residents were supported by about 600 shiploads of supplies from the US every month. To simply maintain the population, without considering occupation troops, would have been beyond the capacity of Japan. As nothing of any major value was produced in T.H. an occupation would effectively reduce the Japanese merchant fleet available for other operations by 1200, as each ship would return to the Home Islands or other destination in ballast. I imagine the US Submarine Service would have been happy to help them find their way "home".
The population of Hawaii in 1941 was roughly 425,000 persons. If you subtract the Hawai'ian Nisei who probably would have been allowed to stay, that’s still a lot of people to move and I don’t think the Japanese had the maritime capability to move even a fraction of that number. Besides, where would this “excess” population have been moved to? I can see the need for putting the captured male population to work in Japan, but what would they have done with the women and children and the elderly?
If the Japanese had occupied Hawaii, the submarine force would have been pushed back to the west coast of the U.S. The transit time for a Gato class submarine (based on personal experience) from San Diego to Yokosuka, Japan was around three weeks. A six week round trip would have used up most of the boat’s fuel and would not have allowed for much time on station. In other words, with Hawaii occupied, submarine patrols in Empire waters from the west coast would not have been particularly effective from a cost-benefit standpoint. The transit time from San Diego to Hawaii, however, is only eight days. That shortened distance with the resultant increase in the possible number of patrols with more time on station, would I think, have permitted the U.S. Navy to enforce a very, very effective blockade of Hawai'i.
You might argue that shore based Japanese aircraft could have unsealed such a blockade. It is very difficult to find a submarine with aircraft. Our own postwar ASW exercises proved that. Twenty years after the end of World War II, even with the latest technological advances (e.g. sonobuoys), more often than not, the only way for the aircraft to “win” an exercise (even against a diesel boat) was for the submarine to “pop smoke” and reveal its position.
Also, with regard to a Japanese occupation of Hawaii, how many troops could they have allotted to occupation duties? How many troops would they have needed to maintain an effective defense? Remember, there are eight major Hawai’ian islands with 750 miles of coastline. Once the U.S. had had time to rebuild it's carrier force, command of the air space over Hawai'i would have passed back to the U.S. leaving the Japanese occupation forces very exposed at the end of a long and tenuous supply line. Occupying Hawai'i would have been a big gamble for the Japanese. Would they have recognized it as such and still proceeded? Perhaps it's a question for which there is no answer.