Matsuoka, Oshima fail in diplomacy with the Tripartite Pact

   Those mainly responsible

 Some conservatives argue that the war against the United States was a “war of self-defense” for Japan. They base their arguments on the United States’ oil embargo and the Hull Note of November 26, 1941, which was considered a de facto ultimatum delivered to Japan by U.S. Secretary of State Cordell Hull shortly before the start of the war. However, the U.S. pressure on Japan to suspend its military advance in China came about, to a large extent, from Japan’s “misjudgments.” Japan in a sense drove itself over the precipice. So, who made the misjudgments and why?

 First of all, the most critical mistake was the conclusion of the Tripartite Pact with Germany and Italy in September 1940. Foreign Minister Yosuke Matsuoka, an enthusiastic proponent of the treaty, originally planned to demand that the United States make concessions by means of forming a four-nation entente by adding the Soviet Union to the Tripartite Pact countries. However, the Tripartite Alliance was nothing but a military pact against the United States. The United States, which by then had imposed economic sanctions against Japan, had further hardened its attitude toward Japan. Furthermore, around the time the treaty was concluded, Germany abandoned its plan to invade the British homeland and was steeling itself for war with the Soviet Union.

 When Matsuoka’s plan to win U.S. concessions collapsed due to the outbreak of the war between Germany and the Soviet Union, Japan could have chosen to abolish the Tripartite Pact and improve relations with the United States. However, Hiroshi Oshima, Ambassador to Germany, continually sent misleading information to Japan, blindly believing Germany would win the war against the Soviet Union. He kept on sending information depicting the war situation as being favorable for Germany. For instance, immediately after the hostilities started he said, “The war will end in four weeks [with victory for Germany].”

 Toshio Shiratori, Ambassador to Italy, proposed “innovative diplomacy.” He lacked the ability to make levelheaded judgments on international situations due to his pro-German, anti-U.S. attitude. Consequently, he also gave the government flawed diplomatic advice. The Navy, because of fears of a possible war with the United States, resisted Japan’s joining the Tripartite Alliance. However, Navy Minister Koshiro Oikawa finally changed his mind and supported the treaty.

 The Army had been promoting the alliance plan since the first Cabinet of Fumimaro Konoe and the Cabinet of Kiichiro Hiranuma. To successfully overthrow the Cabinet of Mitsumasa Yonai, a leading figure in the Navy who was cautious about the treaty, the Army had War Minister Shunroku Hata submit a letter of resignation. The Army abused the system of appointing active-duty military officers to military ministers’ posts. Actively moving behind the scenes was, among others, chief of the Military Affairs Bureau at the War Ministry Akira Muto.

 A mistake comparable with the Tripartite Alliance was the advance into southern French Indochina in July 1941. The United States, which was wary about Japan’s push southward, repeatedly warned Tokyo. Immediately before Japan’s advance into southern French Indochina, Japanese Ambassador to Washington Kichisaburo Nomura was sending telegrams on the possibility of an oil embargo. The Navy led the advancement into southern French Indochina. Chief of the Naval General Staff Admiral Osami Nagano strongly advocated advancing into southern French Indochina. To take control of oil resources in the Dutch East Indies militarily, it was necessary to capture British Malaya, where British bases were located. And, for that purpose, Nagano’s plan posited the imperative of building bases in southern French Indochina.

 However, it was quite evident that a war against Britain would develop into a war against the United States because the United States was about to enter the European theater. Nagano’s judgment was grossly affected by mid-career naval staff officers who were mostly pro-German and anti-American. Chief of the Second Section of the Naval Affairs Bureau of the Navy Ministry Shingo Ishikawa said, “Even against the United States, we will be invincible.” He was considered a leader of such officers. Ishikawa drafted a written opinion to urge Nagano and others to resolutely advance into southern French Indochina. Ishikawa also erred in his assessment of the national strength of the United States. He under-estimated the United States in terms of material national strength, an important factor for judging whether Japan could go to war with the United States. As a result, he also under-estimated the possible damage the U.S. military could cause to Japanese cargo and oil carriers.

 The Tripartite Alliance was led by a Matsuoka group while the advancement to and stationing in southern French Indochina was mainly led by Nagano and others. Nevertheless, it was Prime Minister Konoe who made the final decisions to implement these strategies as national policies and led Japan to war with the United States.