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A series of events led to the attack on Pearl Harbor. War between Japan and the United States had been a possibility that each nation's military forces planned for since the 1920s, though real tension did not begin until the 1931 invasion of Manchuria by Japan. Over the next decade, Japan expanded slowly into China, leading to the Second Sino-Japanese war in 1937. In 1940 Japan invaded French Indochina in an effort to embargo all imports into China, including war supplies purchased from the U.S. This move prompted the United States to embargo all oil exports, leading the Imperial Japanese Navy (IJN) to estimate it had less than two years of bunker oil remaining and to support the existing plans to seize oil resources in the Dutch East Indies. Planning had been underway for some time on an attack on the "Southern Resource Area" to add it to the Greater East Asia Co-Prosperity Sphere Japan envisioned in the Pacific. The Philippine islands, at that time an American territory, were also a Japanese target. The Japanese military concluded an invasion of the Philippines would provoke an American military response. Rather than seize and fortify the islands, and wait for the inevitable U.S. counterattack, Japan's military leaders instead decided on the preventive Pearl Harbor attack, which they assumed would negate the American forces needed for the liberation and reconquest of the islands. Planning for the attack on Pearl Harbor had begun in very early 1941, by Admiral Isoroku Yamamoto. He finally won assent from the Naval High Command by, among other things, threatening to resign. The attack was approved in the summer at an Imperial Conference and again at a second Conference in the fall. Simultaneously over the year, pilots were trained, and ships prepared for its execution. Authority for the attack was granted at the second Imperial Conference if a diplomatic result satisfactory to Japan was not reached. After final approval by Emperor Hirohito the order to attack was issued at the beginning of December. ==Background to conflict== Tensions between Japan and the prominent Western countries (the United States, France, Britain and the Netherlands) increased significantly during the increasingly militaristic early rule of Emperor Hirohito. Japanese nationalists and military leaders increasingly influenced government policy, promoting a Greater East Asia Co-Prosperity Sphere as part of Japan's alleged "divine right" to unify Asia under Hirohito's rule.〔The effort to establish the Imperial Way (''kōdō'') had begun with the Second Sino-Japanese War (called ''seisen'', or "holy war", by Japan). Bix, Herbert, ''Hirohito and the Making of Modern Japan'', 2001, p.326-327.〕 During the 1930s, Japan's increasingly expansionist policies brought it into renewed conflict with its neighbors, Russia and China (Japan had fought the First Sino-Japanese War with China in 1894-95 and the Russo-Japanese War with Russia in 1904-05; Japan's imperialist ambitions had a hand in precipitating both conflicts). In March 1933, Japan withdrew from the League of Nations in response to international condemnation of its conquest of Manchuria and subsequent establishment of the Manchukuo puppet government.〔(【引用サイトリンク】url=http://www.ibiblio.org/pha/policy/pre-war/330327a.html )〕 On January 15, 1936, Japan withdrew from the Second London Naval Disarmament Conference because the United States and Great Britain refused to grant the Japanese Navy parity with theirs.〔Lester H. Brune and Richard Dean Burns, ''Chronological History of U.S. Foreign Relations: 1932-1988'', 2003, p. 504.〕 A second war between Japan and China began with the Marco Polo Bridge Incident in July 1937. Japan's 1937 attack on China was condemned by the U.S. and several members of the League of Nations including Britain, France, Australia and the Netherlands. Japanese atrocities during the conflict, such as the notorious Nanking Massacre that December, served to further complicate relations with the rest of the world. The U.S., Britain, France and the Netherlands each possessed colonies in East and Southeast Asia. Japan's new military power and willingness to use it threatened these Western economic and territorial interests in Asia. Beginning in 1938, the U.S. adopted a succession of increasingly restrictive trade restrictions with Japan. This included terminating its 1911 commercial treaty with Japan in 1939, further tightened by the Export Control Act of 1940. These efforts failed to deter Japan from continuing its war in China, or from signing the Tripartite Pact in 1940 with Nazi Germany and Fascist Italy, officially forming the Axis Powers. Japan would take advantage of Hitler's war in Europe to advance its own ambitions in the Far East. The Tripartite Pact guaranteed assistance if a signatory was attacked by any country not already involved in conflict with the signatory; this implicitly meant the U.S. By joining the pact, Japan gained geopolitical power and sent the unmistakable message that any U.S. military intervention risked war on both of her shores—with Germany and Italy on the Atlantic, and with Japan on the Pacific. The Roosevelt administration would not be dissuaded; believing the American way of life would be endangered if Europe and the Far East fell under military dictatorship, it committed to help the British and Chinese through loans of money and materiel, and pledged sufficient continuing aid to ensure their survival. Thus, the United States slowly moved from being a neutral power to one preparing for war.〔Parkes, Henry Bamford. ''Recent America, A History Of The United States Since 1900'' (Thomas Y. Crowell Company, 1946)Page. 635-645〕 On October 8, 1940, Admiral James O. Richardson, Commander in Chief, Pacific Fleet, provoked a confrontation with Roosevelt by repeating his earlier arguments to Chief of Naval Operations Admiral Harold R. Stark and Secretary of the Navy Frank Knox that Pearl Harbor was the wrong place for his ships. Roosevelt believed relocating the fleet to Hawaii would exert a "restraining influence" on Japan. Richardson asked the President if the United States was going to war. Roosevelt's view was:
Japan's 1940 move into Vichy-controlled Indochina further raised tensions. When combined with its war with China, withdrawal from the League of Nations, alliance with Germany and Italy and increasing militarization, the move provoked an attempt to restrain Japan economically. The United States embargoed scrap metal shipments to Japan and closed the Panama Canal to Japanese shipping.〔Hsu Long-hsuen and Chang Ming-kai, translated by Wen Ha-hsiung. ''History of The Sino-Japanese War (1937-1945)'', 2nd ed. (Taipei, Republic of China: Chung Wu Publishing, 1971), p.317, "Invasion of French Indochina".〕 This particularly hit Japan's economy hard because 74.1% of Japan's scrap iron came from the United States in 1938. Also, 93% of Japan's copper in 1939 came from the United States. In early 1941, Japan moved into southern Indochina,〔Bix, Herbert, ''Hirohito and the Making of Modern Japan'', 2001, p.395〕 thereby threatening British Malaya, North Borneo and Brunei. Japan and the U.S. engaged in negotiations during the course of 1941 in an effort to improve relations. During these negotiations, Japan considered withdrawal from most of China and Indochina after drawing up peace terms with the Chinese. Japan would also adopt an independent interpretation of the Tripartite Pact, and would not discriminate in trade, provided all other countries reciprocated. However, these compromises in China were rejected by General Tojo, then War Minister.〔(Chapter V: The Decision for War ) Morton, Louis. Strategy and Command: The First Two Years〕 Responding to continuing aggression in China, the U.S. froze Japanese assets on July 26, 1941, and on August 1 established an embargo on oil and gasoline exports to Japan.〔Bix, p. 401; Worth, Roland H., Jr., ''No Choice But War: the United States Embargo Against Japan and the Eruption of War in the Pacific'' (Jefferson, North Carolina: McFarland, 1995). ISBN 0-7864-0141-9〕 The oil embargo was an especially strong response because oil was Japan's most crucial import, and more than 80% of Japan's oil at the time came from the United States.〔Yuichi Arima, (The Way to Pearl Harbor: U.S. vs Japan ), ICE Case Studies Number 118, December, 2003 (accessed April 10, 2006).〕 Japanese war planners had long looked south, especially to Brunei for oil and Malaya for rubber and tin. The Navy was (mistakenly) certain any attempt to seize this region would bring the U.S. into the war,〔Peattie, Mark R. & Evans, David C. ''Kaigun: Strategy, Tactics, and Technology in the Imperial Japanese Navy'' (Annapolis: Naval Institute Press, 1997).〕 but the complete U.S. oil embargo removed any hesitancy. Moreover, any southern operation would be vulnerable to attack from the Philippines, then a U.S. commonwealth, so war with the U.S. seemed necessary in any case. In the autumn of 1940, Japan requested 3.15 million barrels of oil from the Dutch East Indies, but received a counteroffer of only 1.35 million. Therefore, the Japanese were interested in expansion to the East Indies, but Malaya and the Philippines had to have been cleared in order for the Japanese to secure the area. This meant inevitable U.S. intervention. After the embargoes and the asset freezes, the Japanese ambassador to Washington, Kichisaburō Nomura, and U.S. Secretary of State Cordell Hull held multiple meetings in order to resolve Japanese-American relations. No solution could be agreed upon for three key reasons: # Japan honored its alliance to Germany and Italy through the Tripartite Pact. # Japan wanted economic control and responsibility for southeast Asia. # Japan refused to leave mainland China (without Manchoukuo).〔La Feber, Walter. Polenberg, Richard ''The American Century, A History Of The United States Since the 1890s'' (John Wiley & Sons, Inc.), pp. 243-247〕 The U.S. embargoes gave Japan a sense of urgency. It would either have to agree to Washington's demands or use force to gain access to the resources it needed. In their final proposal on November 20, Japan offered to withdraw its forces from southern Indochina and not to launch any attacks in southeast Asia provided that the U.S., Britain, and the Netherlands ceased aiding China and lifted their sanctions against Japan.〔 The American counterproposal of November 26 (the Hull note) required Japan to evacuate all of China, without conditions, and to conclude non-aggression pacts with Pacific powers. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Events leading to the attack on Pearl Harbor」の詳細全文を読む スポンサード リンク
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