I think the original SH did it best. You were just put into your general geographical patrol area like the South China Sea, Caroline Islands or Empire Waters with so much fuel subtracted. It's not like American subs had to run a gauntlet of land-based air and roving Hunter-Killer groups like the Germans did in the Atlantic to get to and from port. The journey to the patrol areas from Pearl or Brisbane was usually rather uneventful.
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