Mabe something that has to do with the fact that near the end of the war, US Submarines devastated japanese convoys that carried much needed material, (i.e. oil and other supplies) kind of like germany's u-boat campaign exept that japan didn't introduce an effective convoy system until late in the war, i guess a wonder for the japanese (i.e. supply lines) and a u.s. researchable tech (i.e. sub warfare) that cancells out the japanese wonder thus crippling their production
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