Attack on Pearl Harbor

File:USSArizonaPearlHarbor.jpg

USS Arizona burned for two days after being hit by a Japanese bomb. Parts of the ship were salvaged, but the wreck remains at Pearl Harbor to this day.

On the morning of December 7, 1941, planes and 'mini-submarines' of the Imperial Japanese Navy carried out a surprise assault on the American Navy base at Pearl Harbor, and against the Army Air Corps and Marine air fields nearby on Oahu, Hawaii Territory, now Hawaii. This attack has been called the Bombing of Pearl Harbor and the Battle of Pearl Harbor but, most commonly, the Attack on Pearl Harbor or simply Pearl Harbor.

Overview

The Japanese fleet steamed towards Pearl Harbor undetected until the last moment.

On November 26 a fleet including six aircraft carriers commanded by Japanese Vice Admiral Chuichi Nagumo left Hitokappu Bay headed for Pearl Harbor under strict radio silence.

On the morning of December 7, 1941, that fleet's planes bombed all the US military air bases on the island (the biggest was the US Army air base at Hickam Field), and many of the ships anchored at Pearl, including "Battleship Row". Nearly every plane on the ground was destroyed; only a few fighters got airborne and offered any opposition. Twelve battleships and other ships either were sunk or damaged, 188 aircrafts were destroyed, 155 were damaged and 2,403 Americans lost their lives. The battleship USS Arizona exploded and sank with a loss of over 1,100 men, nearly half of the Americans dead. Its hull became, and remains, a memorial to those lost that day.

File:Pearl Harbor bombings.jpg

The two attack sorties flown by the Japanese approached from different directions. The US radar which detected them 200 miles away was at the top of this map.

The first shots fired and the first casualties in the Attack on Pearl Harbor actually occurred when the USS Ward attacked and sank a Japanese midget submarine. There were 5 Ko-hyoteki class midget submarines which planned to torpedo US ships after the bombing started. None of the subs made it back safely, and only four out of the five have since been found. Of the ten sailors aboard the five submarines, nine died and the only survivor, Kazuo Sakamaki, was captured; he became the first prisoner of war captured by the Americans in WWII.

Recent photographic analysis by the United States Naval Institute indicates a high likelihood that one midget submarine managed to enter the harbor, and successfully fired a torpedo into the USS West Virginia. The final disposition of this submarine is unknown. [1]

The Japanese aircraft carriers were: Akagi, Hiryu, Kaga, Shokaku, Soryu, Zuikaku. Together they had a total of 441 planes, including fighters, torpedo-bombers, dive-bombers, and fighter-bombers. Of these, 55 were lost during the battle. The planes attacked in two waves, and Admiral Nagumo decided to forego a third attack in favor of withdrawing.

Strategy

The purpose of the attack on Pearl Harbor was to neutralize American naval power in the Pacific, if only temporarily. 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 of 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 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 Short at Pearl 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).

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.

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 greivous 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.

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.

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.

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.

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.

Aftermath

Despite the perception of this battle as a devastating blow to America, only five ships were permanently lost to the Navy. These were the battleships USS Arizona, USS Oklahoma, the old battleship USS Utah (then used as a target ship), and the destroyers USS Cassin and USS Downes; nevertheless, much usable material was salvaged from them, including the two aft main turrets from the Arizona. Four ships sunk during the attack were later raised and returned to duty, including the battleships USS California, USS West Virginia and USS Nevada. Of the 22 Japanese ships that took part in the attack, only one survived the war.

There are many who say that the Japanese would have been wise to have attacked with a third strike to destroy the oil storage facilities, machine shops and dry docks at Pearl Harbor, including several senior officers on Nagumo's ships or flying in the strikes. Destruction of these facilities would have greatly increased the US Navy's difficulties as the nearest immediately usable Fleet facilities would have been several thousand miles east of Hawaii on the West Coast of the States. Admiral Chuichi Nagumo declined to order a third strike for several reasons.

losses during the second strike had been more significant than during the first, a third strike could have been expected to suffer still worse losses.
the first two strikes had essentially used all the previously prepped aircraft available, so a third strike would have taken some time to prepare, allowing the Americans time to, perhaps, find and attack Nagumo's force. The location of the American carriers was and remained unknown to Nagumo.
the Japanese pilots had not practiced attack against the Pearl Harbor shore facilities and organizing such an attack would have taken still more time, though several of the strike leaders urged a third strike anyway.
the fuel situation did not permit remaining on station north of Pearl Harbor much longer. The Japanese were acting at the limit of their logistical ability to support the strike on Pearl Harbor. To remain in those waters for much longer would have risked running unacceptably low on fuel.
the timing of a third strike would have been such that aircraft would probably have returned to their carriers after dark. Night operations from aircraft carriers were in their infancy in 1941, and neither the Japanese nor anyone else had developed reliable technique and doctrine.
the second strike had essentially completed the entire mission, neutralization of the American Pacific Fleet.
there was the simple danger of remaining near one place for too long. The Japanese were very fortunate to have escaped detection during their voyage from the Inland Sea to Hawaii. The longer they remained off Hawaii, the more danger they were in, e.g., from a lucky US Navy submarine, or from the absent American carriers.
the carriers were needed to support the main Japanese attack, toward the "Southern Resources Area", where they were intending to capture oil and other supplies. The Japanese government had been reluctant to allow the attack at all as it took air cover from the southern thrust, and Nagumo was under strict orders not to risk his command any more than necessary. As the war games during the planning of the attack had predicted that 2-4 carriers might be lost in the attack Nagumo must have been very happy to suffer no losses, and didn't want to push his luck.

Despite the debacle of unpreparedness including locked ammunition lockers, undispersed aircraft, etc, there were American military personnel who served with distinction in the incident. An ensign got his ship underway from a dead start during the attack. One ship got underway with only four officers onboard, all ensigns, none of which had more than a year's sea duty. That destroyer operated for four days at sea before her commanding officer caught up with her. Probably the most famous is Doris Miller, an African-American sailor who went beyond the call of duty during the attack when he took control of an unattended machine gun and used it in defense of the base. He was awarded the Navy Cross. Anti-aircraft performance during the second strike was much improved over that during the first. Two/thirds of the Japanese losses happened during the second wave.

The attack has been depicted numerous times, not usually very accurately, on film. Examples include:

The surprise attack on Pearl Harbor and the resulting state of war between Japan and the United States were factors in the later Japanese internment in the western United States. Another important factor were the racial views of General John DeWitt, commander of the West Coast Defense District. He claimed existence of evidence of sabotage and espionage intentions among the Japanese and Japanese descended in support of his recommendation to President Roosevelt that those of Japanese descent be interned. He had no such evidence.

In 1991, it was rumored that Japan was going to make an official apology to the United States for the attack. The apology did not come in the form many expected, however. The Japanese Foreign Ministry released a statement that said Japan had intended to make a formal declaration of war to the US at 1 P.M., twenty-five minutes before the attacks at Pearl Harbor were scheduled to begin. (It appears that the Japanese government was referring to the "14-part message, which did not even formally break off negotiations, let alone declare war.) However, due to various delays, the Japanese ambassador was unable to make the declaration until well after the attacks had begun. For this, the Japanese government apologized. The Japanese records admitted into evidence during the Congressional Hearing show that the Japanese had not ever written a declaration of war until after they heard of the successful attack on Pearl Harbor. It would be difficult for them to deliver a document that had not yet been written. The two-line declaration of war was delivered to Ambassador Grew about ten hours after the attack was over. He was allowed to tranmit it to the United States where it was received late Monday afternoon.

The only US ship still afloat today that participated in the attack is the USCGC Taney.

Advance-knowledge debate

There has been considerable debate ever since December 8, 1941, as to how and why the United States had been caught unaware, 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.

For instance, one position — prominently discussed in Stinnet's recent book — suggests that a memorandum prepared by Office of Naval Intelligence Lieutenant Commander Arthur McCollum for its Director, and passed to Captains Walter Anderson and Dudley Knox, two of Roosevelt's military advisors on October 7, 1940 was central to US Government policy in the immediate pre-war period. The memo suggests that only a direct attack on US interests would sway the American public to favor direct involvement in the European war, specifically in support of the British. Anderson and Knox offered eight specific plans to aggrieve the Japanese Empire, writing: "If by these means Japan could be led to commit an overt act of war, so much the better." There is no evidence available to suggest that Roosevelt ever saw the memo. And, of the eight "plans" offered in the memo, only one was ever implemented in any fashion, and there is considerable doubt that the memo was the source of the inspiration for that implementation. The text of the memo is available here.

Examination of information released since the War has revealed that there was considerable intelligence information available to US, and other, officials. It was the failure to process and use this information effectively that has led some to invoke conspiracy theories rather than a less interesting mix of mistake and incompetence. The US government had nine official enquiries into the attack – the inquiry by Secretary of the Navy Knox (1941), the Roberts Commission (1941–42), the Hart Inquiry (1944), the Army Pearl Harbor Board (1944), the Naval Court of Inquiry (1944), the Hewitt investigation, the Clarke investigation, the Congressional Inquiry (1945–46) and the top-secret inquiry by Secretary Stimson authorized by Congress and carried out by Henry Clausen (the Clausen Inquiry (1945)).

One factor making an attack against Pearl Harbor 'unthinkable' was the shallow anchorage at Pearl Harbor. Such depths were generally considered to make effective torpedo attack impossible; at the time, torpedoes dropped from planes went deep before attaining running depth and in too shallow water (like Pearl Harbor) would hit the bottom, exploding prematurely, or just digging into the mud. But the British had proved that modified torpedoes could manage in shallow water during their attack on the Italian Navy at Taranto on November 11, 1940. The US Navy discussed this new development (documents to be linked soon), but as Taranto was about 75 feet deep and Pearl was generally less than 40, it was not considered that the British attack method could be used in Hawaii. The RN had used Swordfish torpedo planes, and their slow speed was part of the reason the Taranto attack succeeded. The IJN had no torpedo planes that could fly that slowly and stay in the air. The Japanese had independently developed shallow water torpedo modifications during the planning and training for the raid in 1941. Daniel Martinez published drawings of the wooden fins attached to the torpedoes in the Dec. 1991 issue of Naval History Magazine. The fins kept the torpedo level in the air and broke off when they hit the water. The level flight of the torpedoes helped keep them from "porposing" and sticking their nose in the mud. This very simple modification of the Japanese torpedoes was completely unexpected by the USN, who had the most abyssmal torpedoes in the war.

US signals intelligence in 1941 was both impressively advanced and uneven. The US MI8 cryptographic operation in New York City had been shut-down by Henry Stimson (Hoover's newly appointed Secretary of State), which provoked its now ex-director, Herbert Yardley, to write a book (The American Black Chamber) about its successes in breaking other nations' crypto traffic. Most responded promptly by changing (and generally improving) their cyphers and codes, forcing other nations to start over in reading their signals. The Japanese were no exception. Nevertheless, US cryptanalytic work continued after Stimson's action in two separate efforts by the Army's Signal Intelligence Service (SIS) and the Office of Naval Intelligence's (ONI) crypto group, OP-20-G. The US was able, in the period just before December 1941, to read several Japanese codes and ciphers. By late 1941, those groups had broken several Japanese cyphers (mostly diplomatic ones, eg 'PA-K2' and the 'Purple Code') and had made some progress against some naval codes/cyphers (eg, the pre-December version of JN-25), but very little against Japanese Army traffic. In fact, the break of the Purple cypher was a considerable cryptographic triumph and proved quite useful later in the War. It was the highest security Japanese Foreign Office cypher, but prior to Pearl Harbor carried little information about future events planned by the Japanese; the military, who were essentially determining policy for Japan, didn't trust the Foreign Office and left it, 'out of the loop'. Unfortunately, the two US groups generally competed rather than cooperated, and distribution of intelligence from the military to US civilian policy-level officials was poorly done (capriciously chosen and distributed), and furthermore done in a way that prevented any of its recipients from developing a 'larger sense' of the meaning of the decrypts.

Japanese intelligence efforts against Pearl Harbor included at least two German Abwehr agents, one of them, Otto Kuhn, a sleeper agent living in Hawaii with his family; he and they were essentially incompetent. The other, Dusko Popov a Yugoslavian businessman, was thought quite effective by the Abwehr, but was actually a double agent whose loyalty was to the British. He worked for the XX Committee of MI5. In August 1941 he was tasked by the Abwehr with specific questions about Pearl (see John Masterman's book on the Double Cross operation for the text of the questionnaire), but the FBI seems to have evaluated the effort as of negligible importance. There has been no report that its existence, or even Popov's availability as a double agent, was passed on to US military intelligence or to civilian policy officials. J. Edgar Hoover dismissed Popov's importance noting that his British codename, Tricycle, was connected with his sexual tastes. In any case, he was not allowed to continue on to Hawaii and to develop more intelligence for the UK and US.

Throughout 1941, the US, Britain, and Holland collected a considerable range of evidence suggesting that Japan was heading for war against someone new. But the Japanese attack on the US in December was essentially a side operation to the main Japanese thrust south against Malaya and the Philippines — many more resources, especially Imperial Army resources, were devoted to these attacks as compared to Pearl. Many in the Japanese military (both Army and Navy) had disagreed with Yamamoto's idea of attacking the US Fleet at Pearl Harbor when it was first proposed in early 1941, and remained reluctant through the Imperial Conferences in September and November which first approved it as policy, and then authorized the attack. The Japanese focus on South-East Asia was quite accurately reflected in US intelligence assessments; there were warnings of attacks against Thailand (the Kra Peninsula), against Malaya, against French Indochina, against the Dutch East Indies, even one against Russia. There are reports of concern at the Pentagon and in the White House about Japanese plans for the SE Asian region. There had even been a specific claim of a plan for an attack on Pearl Harbor from the Peruvian Ambassador to Japan in early 1941. (The source for this bit of intelligence has been traced to the Ambassador's Chinese cook. How he could have gotten that information in not known.) Since not even Yamamoto had yet then decided to even argue for an attack on Pearl Harbor, discounting US Ambassador Grew's report to Washington about it, in early 1941, was quite sensible. Later reports from a Korean organization also seem to have been regarded as unlikely. There has been no report of a serious conviction by anyone in US or UK military intelligence or among US civilian policy officials, prior to the attack, that Pearl Harbor or the US West Coast would be attacked. The so-called "Winds Code" announcing the direction of new hostilities remains a curious and confused episode, demonstrating the uncertainty of meaning inherent in most intelligence information, and in this case, even uncertainty about the existence of some intelligence information, especially some years after the event. It is known, however, that the Winds system was to be implemented only if the communications between Japan and Washington were cut, and they were never out of touch with their embassy prior to the attack. Given this any talk of intercepted "Winds" messages would appear to be specious.

Nevertheless, in late November, both the US Navy and Army sent clear and explicit war warnings to all Pacific commands. Uniquely among those Pacific commands, the local Hawaii commanders, Admiral Kimmel and General Short did little to prepare for war, including an attack on their forces, in their command areas. Inter-service rivalries between Kimmel and Short did not improve the situation.

As Nagumo's attacking force neared Hawaii, there is claimed to have been a flurry of later warnings to US intelligence and, even, directly to the White House or to White House connections. For instance, the SS Lurline, heading from San Francisco to Hawaii on its regular route, is said to have heard and plotted unusual radio traffic. That traffic is further said to have been from the approaching Japanese fleet. There are problems with this. All surviving officers from Nagumo's ships claim that there was no radio traffic to have been overheard by anyone; their radio operators had been left in Japan to fake traffic for the benefit of listeners (ie, military intelligence traffic analysts in other countries), and all radios aboard Nagumo's ships were claimed to have been physically locked to prevent inadvertent use and thus remote tracking of the attack force. Unfortunately, neither the Lurline's log (seized by either Navy or Coast Guard officers in San Francisco on its return), nor the original reports to the Navy in Hawaii, have been found, so contemporaneous written evidence of what was recorded about what was heard aboard the Lurline is not now available. ONI is further said to have been aware of the eastwards movement of Japanese carriers from other sources (eg, the Dutch), but nothing in the way of credible, compelling evidence on this point has yet turned up. Each of these points remains controversial. No Japanese officer would disobey orders lightly, and to disobey the radio silence orders would mean that the entire attack force would have been jeopardized. So when some authors claim that the Japanese force suddenly and for no good reason just decided to start chatting up the airwaves you can be sure that their facts are seriously wrong.

Closer to the moment of the attack, the attacking planes were detected and tracked as they approached by an Army radar installation being used for a training exercise. The Opana Point radar station, operated by two enlisted men (Pvts. Lockard and Elliot) ploted the approaching force and then their relief team plotted them returning to their carriers. These radar returns were thought, by the junior officer in charge at the barely operational information center at Pearl Harbor, to be incoming bombers from the mainland, and in fact the bombers did arrive – in the middle of the attack. Additionally, mini-subs were sighted and attacked outside Pearl Harbor and at least one was sunk — all before the planes came within bombing range. If the Army had thought to give the radar plots to the Navy Halsey would taken his carrier north instead of south (the presumed route of the attackers). If he had gone north USS Enterprise would have run into six Japanese carriers looking for the US flattops! Curious fate and dumb luck avoided the loss of 1/3 of the US carriers in the Pacific that day.

Japanese consular officials in Hawaii, including spy and Naval officer Takeo Yoshikawa, had been sending information to Tokyo about conditions in Hawaii, and in Pearl Harbor, for some months. Some of this information was hand delivered to intelligence officers aboard Japanese vessels calling at Hawaii, but some was transmitted back to Tokyo. Many of the messages in this last group were overheard and decrypted; most were evaluated as the sort of intelligence gathering all nations routinely do about potential opponents and not as evidence of an attack plan. None of those currently known, including those decrypted later in the War when there was time to return to those remaining undecrypted, explicitly stated anything about an attack on Pearl; the only exception was a message sent from the Hawaiian Consulate on 6 December, which was not decrypted until after the 7th and which thus became moot. No cable traffic (the usual communication method to/from Tokyo) was intercepted in Hawaii until after David Sarnoff of RCA agreed to assist during a visit to Hawaii immediately before the 7th; such interception was illegal under US law, though it had been going on in New York for some time.

The Japanese had, during the days prior to the attack, asked Yoshikawa to divide the waters of Pearl Harbor into sections to save time and telegraph bills. He could say "six DDs section AA" instead of "six destroyers in the area northwest of Ford Island". Some people have referred to this as the "bomb plot" message. However, the Japanese Navy did not use the "bomb plot", the exact locations of the ships in Pearl were not forwarded to them prior to the attack. If you look at an aerial photo of Pearl Harbor you'll see that a pilot could easily see what ships were where without having someone point them out in a telegram. This photo, from the Naval Historical Center, is a perfect example. Pearl Harbor from the air It also shows how weird is the claim that Japanese residents of Hawaii were chopping 100 foot long arrows in the sugar cane to point the way to Pearl. The ships next to Ford Island are over 400 feet long! A 100 foot arrow would have been invisible.

Locally, Naval Intelligence in Hawaii had been tapping telephones at the Japanese Consulate before the 7th, and overheard a most peculiar discussion of flowers in a call to Tokyo (the significance of which is still publicly opaque and which was discounted in Hawaii at the time), but the Navy's tap was discovered and was disconnected by the Navy in the first week of December. They didn't tell the local FBI about either the tap or its removal; the local FBI agent in charge later claimed he would have had installed one of his own if he'd known the Navy's had been disconnected.

Attack on Pearl Harbor

Overview

Strategy

Background

Immediate outcome

Longer-term effects

US response

Historical significance

Aftermath

Advance-knowledge debate

Further reading

Further reading — alternative theories

See also

Further reading — some reminiscences

External links

Alternative theories