Appendices - Hirohito's War
APPENDIX N: THE ROLE OF OIL IN THE PACIFIC WAR
Oil and the Decision for War: In the context of Japan’s desperate pre-war search for oil it is perhaps not surprising that Japan viewed America’s de facto oil embargo in July 1941 as an existential threat to Japan’s economic fortunes and its ability to sustain an Asian Empire. As historian Louis Morton noted in Command Decisions  “The shortage of oil was the key to Japan’s military situation. It was the main problem for those preparing for war, at the same time, the reason why the nation was moving toward war… Without oil, Japan’s pretensions to empire were empty shadows.”13 Roosevelt was fully aware of the implications of an oil embargo. Joseph Grew, Ambassador to Japan, met Roosevelt twice in the autumn of 1939 and wrote afterwards in his diary, “I also said that if we cut off Japanese supplies of oil and if Japan then finds that she cannot obtain sufficient oil from other commercial sources to ensure her national security, she will in all probability send her fleets down to take the Dutch East Indies.”14
Ultimately the oil embargo was the trigger for Japan’s attack on America; believing that it could obtain all the oil it required from the Dutch East Indies, the Imperial General Staff received Hirohito’s approval for an attack on South Asia and the United States, whose Empire in the Philippines stood in its way – thus enabling, so Japan leaders thought, to sustain its war machine and its empire. It was a fatally flawed assumption. Even before the war Admiral Yamamoto was limiting naval exercises to home waters to conserve oil stocks. In a symbolic gesture Japanese authorities in Tokyo cut oil supplies to the American and British Embassies.
In spite of the importance of oil in Japanese thinking, curiously Yamamoto neglected to target US oil storage facilities at Pearl Harbor. It was a target that was far more important than battleships. “We had about 4.5 million barrels of oil out there,” observed Admiral Nimitz, “and all of it was vulnerable to 0.50 caliber bullets. None of the oil tanks had bomb-proof covers. Had the Japanese destroyed the oil it would have prolonged the war another two years.”15 As Admiral Husband E. Kimmel told the Joint Committee on the Investigation of the Pearl Harbor Attack, “The thing that tied the fleet to the base [Pearl Harbor] more than any one factor was the question of fuel.”16 The failure to target the oil facilities at Pear Harbor was not a mistake of intelligence. As historian Gordon Prange has noted, ‘The Japanese knew all about those oil storage tanks. Their failure to bomb the Fleet’s oil supply reflected their preoccupation with tactical rather than logistical targets…”17 In hindsight the failure to attack US oil facilities at Pearl Harbor can be seen as one of the most significant tactical mistakes of the Pacific War.
As Chart N.5 illustrates, Japanese oil inventories fell from a peak of nearly 50,000 barrels in 1941 to less than 5,000 barrels by 1945. A combination of a lack of technological sophistication to sustain let alone develop the oil fields of the Dutch East Indies combined with an inadequate supply of oil tankers [See Chart C.13], meant that Japan was never able to make up for the oil that it could no longer purchase from the world’s dominant supplier, the United States. It is notable that during the war America became supplier of oil to the world; Standard Oil of New Jersey alone supplied 25 percent of all oil used by the Allies in World War II. By comparison at the end of the war the Japanese Navy was having fill oil bunkers of its battleships with edible soya oil.