On December 8, 1941 (December 7 in Washington, D.C., and Hawaii), Japan started the Pacific War. Why did the negotiations between Japan and the United States fail to avert the war? Was Japan’s “judgment on material national strength” proper? Why did the government of Prime Minister Hideki Tojo, whose mission was supposedly to avert the war by rebuilding the national policies from scratch, fail to do so? This chapter looks at how Japan began the Pacific War.

Numbers game for waging war against U.S.

 To decide to wage a war, the strength of a nation must be logically evaluated. Did Japan make a proper evaluation? The first evaluation of national power in the process of deciding to wage the Pacific War was the emergency supply mobilization program compiled by the Cabinet Planning Board in August 1940 (the 15th year of the Showa Era). The board, placed directly under the Prime Minister, was tasked to study and plan a wartime economy. The study pointed out that if imports from third-party countries stopped, the supply of most basic materials would be cut in half.

 Around the same time, the Navy also made an evaluation of national strength and concluded that the supply of strategic materials would meet the demand only for about a year if its supplies from Britain, the United States and their controlled areas were cut off.

 Hearing such estimates, Navy Minister Zengo Yoshida called for self-restraint at an executive meeting of the Navy Ministry, saying, “The Japanese Navy can fight against the United States for only one year. Going to war where battle could only be sustained for one year would be reckless —like a ferocious tiger rushing into a snare.”

 The War Ministry’s War Plans Section presented its assessment of national strength in March 1941. The assessment was compiled by Major Hideo Shibo whose father-in-law was Sadao Araki who served as War Minister in the early 1930s. After analyzing various data, Shibo concluded it would be difficult to make a southward military advance. However, under Araki’s suggestion, Shibo drafted a report claiming Japan was capable of waging a war. But Kikusaburo Okada, chief of the War Plans Section, revised the report, saying, “It should be noted that it is not certain that the material national strength is adequate to carry out a long war against the United States and Britain.”

 This final report sent shock waves through the Army. The Army General Staff’s Twentieth Group (War Coordination) wrote in its diary log, “We have to say it’s impossible to make a southward advance with military forces.”

 But when the Japanese military advanced into southern French Indochina, and the United States imposed an oil embargo against Japan in August 1941, the idea of averting war significantly receded.

 At that time, Army Colonel Hideo Iwakuro tried to persuade various military and government officials that Japan should avoid a war, based on a report on the disparity of national strength between Japan and the United States. The report, compiled by Army Paymaster Colonel Kenkichi Shinjo who was involved in gathering intelligence about the United States, stated: “If the ratio of industrial strengths of both countries could be kept at the current level, war damage to the United States must be 100 percent while damage to Japan must be limited to less than 5 percent throughout the war.” (See Table)

 In the July 1941 personnel shuffle at the Army General Staff, Takushiro Hattori was appointed chief of the Operations Section and Masanobu Tsuji chief of the Logistics Unit. The appointments marked the reuniting of two key figures who, as staff officers in the Kwantung Army, triggered the Nomonhan Incident that lasted from May to September 1939 in defiance of Army leaders in Tokyo. At the same time, Shinichi Tanaka—who played a key role as the chief of the War Ministry’s Military Affairs Section for the expansion of the war front after the Marco Polo Bridge Incident in July 1937—was serving as head of the Operations Bureau of the Army General Staff. This meant three hard-liners were in charge of operations planning for the Army, and they advocated that Japan should go to war with the United States.

 One of the major points in assessing national strength was how to estimate damage to ships. Ships were needed to secure the transport of supplies such as oil and to secure the sea lanes for such transport. If Japan was to mobilize ships for such a purpose, the United States would naturally start attacking Japanese ships. Therefore, if damage to ships exceeded Japan’s shipbuilding capability, it would become difficult to continue combat operations.

 In June 1941, Shingo Ishikawa, chief of the Navy Ministry’s Second Naval Affairs Section, calculated that the loss of Japanese ships would amount to 600,000 tons per year and the nation’s maximum shipbuilding capability would be 800,000 tons, concluding Japan would be able to deal with damage to ships. However, after Shigeru Fukutome, chief of the Naval General Staff’s Operations Bureau said, “The vessel damage would be 1.4 million tons in the first year of the war [against the United States],” Ishikawa and his colleagues worked to negate Fukutome’s remarks and told the Army that damage to Japanese vessels would be between 800,000 tons and 1 million tons per year on average.

 In actuality, damage to Japanese vessels in the first year was 960,000 tons. The figure increased to 1.69 million tons in the second year and rose to 3.92 million tons in the third year of the war.

 U.S. economist Jerome B. Cohen noted: “For every ton of shipping the Japanese were able to build, three were sunk; and, given the inadequate merchant tonnage with which Japan began the war, her merchant fleet was being whittled down to nothing.”  Cohen saw Japan’s ability in calculating its war capacity as “characterized by ‘initial overconfidence’ and ‘lack of planning, poor administration and internal conflict of interests.’”  The economist pointed out: “Japan was singularly lacking in foresight.”

 The final national strength judgment was made by the Cabinet Planning Board immediately after the inauguration of the Tojo Cabinet in October 1941. The President of the board—the state ministerial position—was Army General Teiichi Suzuki. In August 1941, Suzuki had reported, “If a war broke out and Japan succeeds in taking control of oil producing areas in the Dutch East Indies, oil bases will be destroyed immediately and it will be difficult to obtain oil.”

 But Suzuki later changed his view. At an Imperial conference meeting attended by the Emperor on November 5, he presented a view that Japan would “narrowly maintain a self-sustaining system” given the domestic oil reserves and oil to be obtained in the southward advance. “To maintain the current situation [by not going to war] will put the nation at a disadvantage, even looking at just the material aspects,” Suzuki added. This assessment was made based on mere number shuffling by the Army and Navy, and Suzuki’s view played a major role in bringing Japan into the war.

 At a meeting of the Emperor and jushin—unofficial senior advisers to the Emperor, including former Prime Ministers—on November 29, former Prime Minister Keisuke Okada said, “It is quite worrisome whether we can be confident of winning the war from the viewpoint of our ability to supply goods.”

 Former Prime Minister Mitsumasa Yonai said, “If we go to war to avoid a gradual decline, we may end up with an even bigger decline.”

 As such, many were concerned about Japan’s national strength and were unable to grasp the Unites States’ real power. But Japan continued on its path to war.