Most tankers that had carried oil to Japan before the embargo were already operating on Atlantic and Indian Ocean routes. By October 1941, the two remaining in the Pacific were serving Singapore, Hong Kong, and Australia. Tanker diversion was already under way before Japan entered the wider war, limiting any simple plan to recover those ships for Japanese supply. Oil access depended on the global allocation of merchant hulls as well as on naval action.
Notable Point · 22:05-22:34
Oil-tanker diversion had already narrowed Japan's options
Why prewar tanker reallocation complicates proposals to redirect more shipping toward Japan in late 1941.