Making best use of domestic energy sources: The Priority Production System for coal mining and steel production in post–World War II Japan

One of the main reasons Japan entered World War II was to secure sources of energy in Asia and the Pacific region, particularly oil wells such as the Minas oil field on Sumatra in the Dutch colony of Indonesia. Although oil filled only 10 percent of energy needs in post-World War II Japan, it was indispensable to transportation and the military, so the country had to rely on imported oil, as it had before the war.1 Although there were oil wells on mainland Japan, production of crude oil could meet only a tiny fraction of the country’s energy demands.