The neglected preparation for submarine warfare

An island empire should have treated vulnerable sea routes as a central strategic problem. Orders placed when Nagano took office might have produced one or two dozen escorts by the period of heavy submarine activity. Those ships could have protected the most valuable cargoes in the South China and East China seas, maintaining a minimum flow of supplies for industry and further construction. Better convoy defence probably would not have reversed the war, but it could have kept more Japanese forces operating for longer.