Japan's resource options impose different transport risks

Japan's home islands could not provide the raw materials needed for a prolonged war, so planners considered northern and southern resource areas. The northern option offered a possible route through Korea that reduced the sealift burden and appeared less likely to provoke immediate British or American intervention. The southern option held petroleum and other resources but lay behind the Philippines, Singapore, and the Dutch East Indies, making conflict with Britain and the United States much more likely. Anglo-Dutch commercial interests in those oil fields also gave London a direct strategic concern. Seizing resources and transporting them safely were separate logistical problems, and Japan had not invested enough in shipping for the latter.