A Vulnerable Empire

By April 1942 Japan occupied most of Southeast
Asia and controlled the area's vast resources. Those
resources, however, had to come to Japan by
ship. No major industrial country in the world
was more dependent on its merchant marine than
Japan. Without natural resources and adequate
agricultural land, the Japanese imported
one-third of the total raw materials used by
industry and about 20 percent of the nation's food
supply. Most of the feedstocks for the iron, steel,
aluminum, and chemical industries--all basic to the
manufacture of munitions--came from overseas.
Even more critical, tankers brought in 82 percent
of the petroleum needed to drive the
Imperial Army and Navy.

With U.S. battleships sunk at Pearl Harbor, only
American submarines could challenge Japan's
control of the Pacific.