2 Strategy

300px Battleship Row presented an attractive concentration of targets.

The purpose of the attack on Pearl Harbor was to neutralize American naval power in the Pacific, if only temporarily. Admiral Yamamoto Isoroku himself suggested that even a successful attack would gain only a year or so of freedom of action. Japan had been embroiled in a war with China for some years (starting in 1931) and had seized Manchuria some years before. Planning began for a Pearl Harbor attack in support of further military advances in January 1941, and training for the mission was underway by mid-year when the project was finally judged worthwhile after some Imperial Navy infighting.

Part of the Japanese plans for the attack included breaking off negotiations with the US prior (and only just prior) to the attack. Diplomats from the Japanese Embassy in Washington, including special representative Saburu Kurusu , had been conducting extended talks with the State Department regarding the US reactions to the Japanese move into Indochina in the summer. Just before the attack, a long message was sent to the Embassy from the Foreign Office in Tokyo (encyphered with the Purple machine), with instructions to deliver it to Secretary Hull just before the attack was scheduled to begin (i.e., 1 PM Washington time). Because of decryption and typing delays, the Embassy personnel could not manage to do so; the long message breaking off negotiations was delivered well after the intended time, and well after the attack had actually begun. The late delivery of the note contributed to US outrage about the attack, and is a major reason for

Roosevelt's famous characterization of that day as "... a date which will live in infamy". Yamamoto seems to have agreed; he was unhappy about the botched timing. He is commonly thought to have said, "I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve", but this seems to be a quote made for the movie, Tora! Tora! Tora!. See Isoroku Yamamoto's sleeping giant quote for more information. Even though the quote may not have been said by Yamamoto, it did seem to capture his feelings about the attack.

Both parts of the final message had been decrypted by the US well before the Japanese Embassy had managed to finish, and it was the decrypt of the second part which prompted General George Marshall to send his famous warning to Hawaii that morning — the one that was actually delivered, by a young Japanese-American cycle messenger, to General Walter Short at Pearl Harbor several hours after the attack had ended (there had been difficulties with the Army's communications, and transmission delays by commercial cable, and it had somehow lost its "urgent" marking during its travels).

2.1 Background

The Japanese move into southern Indochina, beginning in mid-1941, provoked the major Powers in the area into action, more than the diplomatic protest notes which had been the usual for nearly a decade: the United States, with Britain and the Dutch colonial government, imposed an embargo on strategic materials, in particular oil and steel, to Japan in July. This threat to the Japanese economy (and to the military's supplies) was intended to force a reconsideration of the move into Indochina and perhaps even to the negotiating table. Roosevelt's decision to leave the Fleet in Pearl (closer to Japan than the US West coast, and so an increase in threat) is said to have been part of this response. Roosevelt regarded it as sufficiently important to relieve Admiral Kimmel's predecessor, Admiral Richardson , when he protested the decision. The US, and other Powers', reactions seem instead to have increased the Japanese military's commitment to a conquer and exploit approach against areas holding the resources endangered by the new embargo. With very limited oil production and minimal refined fuel reserves, Japan faced a real, and serious, problem. The Japanese leadership took the embargo as the stimulus to activate plans to seize supplies of strategic material in Asia, particularly southeast Asia. They could not expect the United States to remain passive when those plans were activated; it was this which had already led Admiral Isoroku Yamamoto to consider ways to preemptively neutralize American power in the Pacific.

His idea of an attack on the naval base at Pearl Harbor was a tactic intended to help achieve this strategic goal. Japanese sources indicate that Yamamoto began to think about a possible strike at Pearl very early in 1941, and that, after some preliminary studies, had managed to get approval to start preliminary operational planning for it some months later. There was substantial opposition to any such operation within the Japanese Navy, and at one point Yamamoto threatened to resign if the operational planning were stopped. Permission to actually set up the operation was given in late summer at an Imperial Conference attended by the Emperor, and permission to actually stage the force into the Pacific in preparation for the attack was given at another Imperial Conference, also attended by the Emperor, in November. The November decision included recall of Nagumo's force only if the US agreed with essentially all of Japan's demands.

2.2 Immediate outcome

The forward magazines of the USS Arizona exploded after she was hit by a bomb dropped by Tadashi Kusumi.

In terms of its strategic objectives the attack on Pearl Harbor was, in the short to medium term, a spectacular success which eclipsed the wildest dreams of its planners and has few parallels in the military history of any era. Due to its grievous losses at Pearl Harbor and in the subsequent Japanese invasion of the Philippines, for the next six months, the United States Navy was unable to play any significant role in the Pacific War. With the US Pacific Fleet essentially out of the picture, Japan was free of worries about the other major Pacific naval power. It went on to conquer southeast Asia, the entire southwest Pacific and to extend its reach far into the Indian Ocean.

2.3 Longer-term effects

In the longer term, however, the Pearl Harbor attack was an unmitigated strategic disaster for Japan. Indeed Admiral Yamamoto, whose idea the Pearl Harbor attack was, had predicted that even a successful attack on the US Fleet would not and could not win a war with the US, as American productive capacity was too large. One of the main Japanese objectives was the three American aircraft carriers stationed in the Pacific, but these were not present - Enterprise was returning, Lexington had sortied a few days prior, and Saratoga was in San Diego following a refit at Puget Sound Naval Shipyard. Putting most of the US battleships out of commission, was widely regarded—in both Navies and by most observers worldwide—as a tremendous success for the Japanese. The elimination of the battleships left the US Navy with no choice but to put its faith in aircraft carriers and submarines, these being most of what was left—and these were the tools with which the US Navy halted and then reversed the Japanese advance. The loss of the battleships turned out to be less important than almost everyone thought before (in Japan) and just after (in Japan and the US) the attack.

President Franklin D. Roosevelt signed the Declaration of War against Japan on the day following the attack.

Probably most significantly, the Pearl Harbor attack immediately galvanized a divided nation into action as little else could have done. Overnight, it united the US with the goal of fighting and winning the war with Japan, and it probably made possible the unconditional surrender position taken by the Allied Powers. Some historians believe that Japan was doomed to defeat by the attack on Pearl Harbor itself, regardless of whether the fuel depots and machine shops were destroyed or if the carriers had been in port and sunk.

2.4 US response

On December 8, 1941, the US Congress declared war on Japan with Jeannette Rankin being the only one dissenting vote. Franklin D. Roosevelt signed the declaration of war shortly afterward, calling the previous day "a date which will live in infamy." The US Government continued and intensified its military mobilization, and started to convert to a war economy.

A related question is why Nazi Germany declared war on the United States December 11, 1941 immediately following the Japanese attack. Hitler was under no obligation to do so under the terms of the Axis Pact, but did so anyhow. This doubly outraged the American public and allowed the United States to greatly step up its support of the United Kingdom, which delayed for some time a full US response to the setback in the Pacific.

3 Historical significance

This battle, like the Battle of Lexington and Concord, had history-altering consequences. It only had a small military impact due to the failure of the Japanese Navy to sink US aircraft carriers, but even if the air carriers had been sunk it would not have helped Japan in the long term. The attack firmly drew the United States and its massive industrial and service economy into World War II, leading to the defeat of the Axis powers worldwide. The Allied victory in this war and US emergence as a dominant world power has shaped international politics ever since.

In terms of military history, the attack on Pearl Harbor foreshadowed the emergence of the aircraft carrier as the center of naval power, replacing the battleship as the keystone of the fleet. However, it was not until later battles in the war, such as the battles of the Coral Sea and Midway, that this breakthrough became apparent to the world's naval powers.

4 Advance-knowledge debate

Main article: Pearl Harbor advance-knowledge debate

There has been considerable debate ever since December 8, 1941, as to how and why the United States had been caught unawares at Pearl Harbor, and how much and when American officials knew of Japanese plans and related topics. Some have argued that various parties (in some theories Roosevelt and/or other American officials, or Churchill and the British, in others all of the above, or additional players) knew of the attack in advance and may even have let it happen, or encouraged it, in order to force America into war.

5 See also

• USS Arizona Memorial

6 Further reading

• The monumental trilogy by Gordon W. Prange and his collaborators Donald M. Goldstein and Katherine V. Dillon, At Dawn We Slept (McGraw-Hill, 1981), Pearl Harbor: The Verdict of History (McGraw-Hill, 1986), and December 7, 1941: The Day the Japanese Attacked Pearl Harbor (McGraw-Hill, 1988), is considered the standard work.
• Walter Lord, Day of Infamy (Henry Holt, 1957) is a very readable, and entirely anecdotal, re-telling of the day's events.
• W. J. Holmes, Double-Edged Secrets: US Naval Intelligence Operations in the Pacific During World War II (Naval Institute, 1979) contains some important material, such as Holmes' point that had the US Navy been warned of the attack and put to sea, it would have likely resulted in an even greater disaster, as all the ships sunk would have been lost completely in deep water anchorages, along with a higher loss of life. At the time of Pearl Harbor, Holmes was an intelligence officer who worked closely with the cryptographers stationed in Hawaii.
• Michael V. Gannon, Pearl Harbor Betrayed (Henry Holt, 2001) is a recent examination of the issues surrounding the surprise of the attack.
• Frederick D. Parker, Pearl Harbor Revisited: United States Navy Communications Intelligence 1924-1941 (Center for Cryptologic History, 1994) contains a quite detailed description of what the Navy knew from intercepted and decrypted Japanese communications prior to Pearl.
• Henry C. Clausen and Bruce Lee, Pearl Harbor: Final Judgement, (HarperCollins, 2001), is an account by Henry Clausen himself of the secret 'Clausen Inquiry' undertaken late in the War by order of Congress to Secretary of War Stimson. Clausen's effort was extraordinary, if only because of the exploding vest he wore as he traveled, and the astonishing letter of authority Stimson gave him. His account supports the 'bumbling around in Washington' and the 'bumbling around in Hawaii' theories, but not the 'Roosevelt/Marshall knew and invited the Japanese in' variant. He also thinks that Kimmel and Short both failed in their duty to be as prepared as they could with the resources they had, after they were ordered to do so in late November. He also faults General Marshall for committing perjury(!). Clausen admired MacArthur despite the losses in MacArthur's area of responsibility (the Philippines) several hours after the raid at Pearl; in part, it seems, because they were both committed Masons. Of course, Clausen's investigative brief from Stimson didn't include being caught by surprise in the Philippines. It's worth reading.

6.1 Further reading — reminiscences

• Robert A. Theobald, Final Secret of Pearl Harbor (Devin-Adair Pub, 1954) BooksEnthsiast.com BooksEnthsiast.com Foreword by Fleet Admiral William Frederick Halsey, Jr.
• Albert C. Wedemeyer, Wedemeyer Reports! (Henry Holt Co, 1958) BooksEnthsiast.com BooksEnthsiast.com
• Hamilton Fish, Tragic Deception: FDR and America's Involvement in World War II (Devin-Adair Pub, 1983) BooksEnthsiast.com

7 External links

• "Pearl Harbor Attacked" Message Board — A wonderful site with lots of personal recollections, etc – see particularly the two "Intelligence" boards, which have a host of useful articles posted
• Naval Institute Special Collections: Pearl Harbor — Articles, books, and pictures
• - Pearl Harbor Mother of all Conspiracies — Extensive research including documents and links.
• - Pearl Harbor Attack Hearings Documentation that refutes the wild theories surrounding the attack. 7,000 pages of original documents.
• Order of battle

U.S. military history 1900-1999 Pearl Harbor

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