National Hari Kari - The Japanese attack on Pearl Harbour

The Soviet Union did not ignore American nuclear armed missiles based in Turkey. The USA did not ignore Soviet nuclear armed missiles based in Cuba. Israel did not ignore the Osirak nuclear reactor in Iraq. President Reagan did not ignore a miliary build up on the island of Grenada. 1930s Britain did not ignore an Italian military build up in East Africa. 1967 Israel did not ignore a massive Egyptian military build up in the Sinai.

Nobody ignores a threatening military buildup on their doorstep. Unless you have historical Japanese documents to prove otherwise I don't believe Japan ignored U.S. heavy bombers and submarines based on Luzon after July 26, 1941.

The main focus of Japan's attention was the domination of Thailand and Malaya, and the neutralization of the "fortress" at Singapore as stepping-stones to assaulting the oil-rich Dutch East Indies. The Philippines threatened the left flank of the forces assigned to the Southern Advance. Rearmament in the Philippines was simply more evidence to Japan of a conspiracy against her. The IJA "hot heads" had been promoting the idea of attacking the West long before the rearmament began, so the arrival of additional forces merely provided stronger evidence (to the IJA leadership) of the need to strike sooner rather than later.

There is a difference between ignoring and being unconcerned. The japanese were of the opinion that they did not require the services of First Air fleet to deal with the military forces being built up in the PI and Malaya. they did not believe that they needed to utilize more than 10 divisions of their 50 division army to subdue the far east. More than half their air forces remained in China, Manchuria and the Home islands during the upcoming campaign. They undertook their southern thrust with just two battleships, six other battleships remained in home waters, mostly to conserve japans dwindling stocks of fuel

Whilst they could not, and did not, ignore the threats posed by the military buildup, they were more than confident that they could deal with the threat. And the record of historical events backs up their assessment.

Beyond that, its up to you to undertake your research and determine if they ignored the threat or went to war because of the threat. There is no evidence that i know of that saw japans decision to go to war as primarily or even partly driven by their fear of the military build ups in the PI and Malaya. What drove them to war were the US led embargoes on strategic materials, particularly oil.

November 16
Washington: MAGIC intercept a cable from Tokyo to Nomura advising him "fate of the Empire hangs by a sheer thread....please fight harder"

Four days later, nomura present Proposal "B" to Secretary Hull. Both sides know it is the "absolutely final offer". Through the MAGIC intercepts, hull is convinced it amounts to an utimatum. The president however instructs Hull to give the submission "sympathetic study".

On November 21, the British Joint Intelligence Committee transmitted to its Far Eastern Command its strategic assessment on future japanese reactions. The assessment is basically that if negotiations break down (by that stage assessed as "likely" by the British), the Japanese are not likley to attack Siberia (I believe they derived that from their reading of Soviet Intelligence, which by then was assimilating Sorges reports), or even Malya or the NEI. attacks against the burma road were considered unlikley. However the assessment considered an invasion of Siam as probable.

This assessment was intercepted by by the Us war department (the US was reading british traffic as well as Japanese) and circulated to various military officials

Richard Sorge the "Ramsay" Spy ringThe spy network built by Sorge was the one that supplied to Moscow some of themost valuable information on both German and japanese intentions. For most of the eight years Sorge spent in Tokyo, the Kremlin regarded Japan as the greatest threat to the Soviet Union. He was so able to cover himself that a japanese reporter described him as a "typical Nazi, arrogant and boastful temper and heavy drinker". But Sorge was an incredibly talented spymaster and was able penetrate the german diplomentic corps in tokyo, to obtain a great deal of information. His chief source of information was the German embassy and he even managed a little extra curricular activity by seducing the ambassador's wife.

Sorge was able to predict the Japanese invasion of China in 1937 and the 1941 German invasion of the Soviet Union, providing to Moscow the exact date – June 22 – of the beginning of the Barbarossa invasion. Information came to him from high-ranking representatives: the german ambassador General Ott, his friend Scholl and an officer of the Reich Colonel Von Niedermayer. But his timely and accurate information was ignored in the paranoia driven Stalinist Russia. Stalin dismissed the informationas as dubious and dangerous. Not being able to get his hands on Sorge, he shot Berzin, the General Commander of Military Intelligence and head of communications service.

A month after the German armored divisions invaded the Soviet Union.

Sorge couldn't believe that; after eight years of risk, hard work and sacrifices, Moscow did not believe his information. As always, he didn't lose his nerve and on July the 2nd 1941 he sent a new message: the japanese army and navy had decided to move their forces in the south-east of Asia in preparation for possible confrontations with the western powers. this offered the opportunity for Soviet troops to concentrate on the Western Front, and led directly to the defeat of the Germans in the battle of Moscow.

In the context of the Pacific war, it is significant to note that a critical element in the Japanese decision to go to war, was that the germans would win against the Soviets. Until December 4 that appeared to be a likley outcome, and if the germans had defeated the Soviets, the outcome in the pacific may well have been different. But partly bewcause of the achievements of this one man, the Soviets were able to redeploy vast numbers of their far Eastern army, and defeat the final German thrusts to take Moscow. Even before the outbreak of war, one of the fundamental pre-requisites for Japans decision to go to war had been checked, and would eventually be defeated.

November 22
MAGIC intercepts reveal Tokyos message to Nomura that the deadline for negotiations had been extended by four days, to November 29. "after that things are automatically going to happen".

Pearl Harbour Strike Force: Waiting at Tankan Bay, Nagumo receives his operational order to sail on November 26 (this message was intercepted by OP-20-G, but could not be read).

First Air fleets preprations for the Attack

"In early 1941, Vice Admiral Isoroku Yamamoto was appointed Commander-in-Chief of Japan's Combined Fleet, and he immediately took issue with the cautious policy of the Japanese Naval General Staff. Yamamoto did not believe that the United States Pacific Fleet would remain idle at Pearl Harbor while Japan attacked and seized America's Philippines, and British and Dutch colonial possessions in South-East Asia. He believed that Japan must cripple the United States Pacific Fleet at the same time as it launched its attacks on countries of South-East Asia.

With this firm conviction, Admiral Yamamoto began to consider a surprise carrier-launched air attack on the United States Pacific Fleet at its Pearl Harbor base timed to coincide with Japan's military aggression in South-East Asia. Yamamoto instructed Rear Admiral Takijiro Onishi, Chief of Staff of the 11th Air Fleet, to assess the feasibility of an attack on Pearl Harbor by carrier-launched aircraft. Onishi enlisted the assistance of Commander Minoru Genda, a brilliant staff officer and tactician serving with Japan's 1st Air Fleet. Genda studied the problem and came to the conclusion that an attack on Pearl Harbor could succeed if (a) the attack took the Americans completely by surprise, (b) the attack occurred early on a Sunday morning when American defence preparedness would be at a low level, (c) all six of Japan's best aircraft carriers were used, and (d) highly skilled aircrews were used in the attack. To ensure complete surprise, Genda's plan precluded alerting the Americans to their danger by a prior declaration of war.

Admiral Yamamoto's plan for a surprise peacetime attack on the United States Pacific Fleet at Hawaii would involve a strike force which included Japan's six largest and most powerful aircraft carriers. His task was made much easier by President Roosevelt's decision to relocate the United States Pacific Fleet from California to Hawaii. As Yamamoto saw it, the destruction of the American Pacific Fleet would give Japan time to seize the Philippines, Malaya, British Borneo, Burma and the Netherlands East Indies (now Indonesia), and gain access to the oil, minerals, rubber and other resources that Japan needed to sustain its aggressive war machine. He was hopeful that, with its Pacific Fleet destroyed or crippled, the Americans would be willing to accept a peace settlement that allowed Japan to keep its new conquests in South-East Asia.

The Japanese Naval General Staff initially rejected Admiral Yamamoto's plan for an attack on Pearl Harbor as being too great a gamble. They doubted that surprise could be achieved when the strike force would be at sea for two weeks before the attack. Japan had eleven aircraft carriers, and the admirals felt that Yamamoto's plan could put at risk their six best carriers. They also felt that diverting Japan's six most powerful aircraft carriers to Hawaii would leave the southern attacks on the Philippines and British Malaya dangerously unprotected. In the end, Yamamoto only overcame their opposition by threatening to resign.

Although the admirals of the Naval General Staff were reluctantly persuaded by Yamamoto to abandon the policy of defensive naval war in favour of attack, the years of night warfare training and the highly accurate, long range torpedoes associated with the defensive policy would give the Japanese Imperial Navy a significant edge over Allied navies in night actions during the Pacific War.

Training for the Pearl Harbor Attack

Early in 1941, despite the fact that the Chief of the Naval General Staff, Admiral Osami Nagano, had not yet approved a surprise attack on Pearl Harbor, Admiral Yamamoto directed that intensive planning and training for such an attack was to be undertaken.

Japanese naval aircrews had already honed their war skills flying sorties against the poorly equipped and trained Chinese air force and army. However, Pearl Harbor offered special challenges to an enemy force proposing to use air-launched torpedoes. The harbor was comparatively shallow and a large area in the centre of the harbor was occupied by Ford Island. The American battleships were moored on the eastern side of Ford Island. The water area between the battleships and the eastern shore of the harbor was narrow. Japanese torpedoes would have to be redesigned for use in shallow harbor waters, and torpedo aircrews would have to learn to drop their torpedoes with great precision so that they would land in the narrow stretch of water between the eastern shore of the harbor and the battleships. The Japanese aircrews went about this training with great enthusiasm and dedication. By November 1941, they were ready for the attack".

November 24

MAGIC reveals that Tokyo is instructing Nomura that as a pre-condition to any agreementthe allies must cease aid to Chiang Kai Shek and lift the oil embargo immediately. Hull seeing this as a hardening of the Japanese position advises the President that the outlook was "critical, and virtually hopeless". the President informs his cabinet "we are likley to be attacked next Monday for the Japs are notorious for attacking without warning" . He cables Churchill "we must all prepre for real trouble, real soon in the Far East"

Significantly, the Allies are expecting an attack in the Far east, but appear oblivious to an attack on the fleet base in Pearl.

However, the Chief of Naval operations flashes a war warning to both the naval commands in Pearl and the PI " SURPRISE AND AGGRESSIVE MOVEMENTS BY JAPAN"

November 25

The presidents war council approves a three month Modus Vivendi despite the presidents concern about how to manouver Japan into firing the first shot

modus vi·ven·di (v-vnd, -d)
n. pl. modi vivendi
1. A manner of living; a way of life.
2. A temporary agreement between contending parties pending a final settlement.

Modus vivendi is a Latin phrase signifying an agreement between those whose opinions differ, such that they agree to disagree.

Modus means mode, way. Vivendi means of living. Together, way of living, implies an accommodation between disputing parties to allow life to go on. It usually describes informal and temporary arrangements in political affairs. For example, where two sides reach a modus vivendi regarding disputed territories, despite political, historical or cultural incompatibilities, an accommodation of their respective differences is established for the sake of contingency. This sense of the term has been used as a keystone in the political philosophy of John Gray.

Diplomatically, a modus vivendi is an instrument for establishing an international accord of a temporary or provisional nature, intended to be replaced by a more substantial and thorough agreement, such as a treaty. It is usually fashioned informally, and so never requires legislative ratification. Typically armistices and instruments of surrender are modi vivendi

November 26


At Dawn the Pearl Harbour Strike Force under the comand of Admiral Nagumo, puts to sea. The final instruction of Yamamoto being "In case negotiations with the US reach a successful conclusion, the task Force will immediately put about and return home".

In Washington, SigInt reports (unspecified) suggest troop convoys had been sighted south of formosa steaming for IndoChina. These reports were taken by the president as "evidence of bad faith on the part of the Japanese". Stark urges that the b-17s in the PI be used to undertake pre-enptive strikes against the transports (another fascinating what if), but he is overruled. There can be little doubt that the the Allies knew in advance of the attacks in the far east, but equally, theee is little to support any assetrions that they knew in advance of the strike heading for Pearl Harbour. American intell is by this stage routinely either misidentifying the location of the Japanese Fleet Carriers, or returning 'location uncertain" reports.

Roosevelts new evidence indicates a secret leak from Japans War Plans Division. As a result of this intelligence, Hull was instructed to drop the State Departments counterproposal for a "Modus Vivendi" to resume oil supplies "on a monthly basis for civilian needs".

That afternoon, Hull advises of the US rejection of Proposal "B". Hull issues a strongly worded document tying any relaxation of the oil embargo to japans acceptance ten specific conditions. These were a reiteration of of the open door policy which in turn required as a prerequisite the 'withdrawal of all military , naval, air and police forces from China and IndoChina".

(One cannot but help to speculate if either proposal "B" or a reduced "Open Door Policy" that involved a temporary ceasefire in China and a withdrawal from Indo China had been suggested)


In Tokyo, Tojo advised his cabinet "This is an Ultimatum", having assumed the ten conditions were indicating that the US was "unyielding and unbending". He saw"no glimmer of hope". Japans embassies and consulates worldwide were warned to destroy codes immediately following the issue of the "war imminent" signal. Such a signal would be hiden in a weather report "NIGASHI NO KESAME", meaning "East Wind Rain". This would indicate hostilities with the west.

November 27

The secretary of state receives Hornbecks assessment "the Japanese Government does not desire or intend or expect to have forthwith armed conflict with the United States. Hornbeck suggests "odds of 5:1 that the US will not be at war on or before December 15". However, Hull knew otherwise. telling the secretary of War he had "washed his hands of itall" and that it was now "in the hands of you and Knox - the army and navy". but in an unprecedented move, Marshall and Stark jointly submit a memorandum to the president, "if the current negotations end without agreement, Japan may attack the Burma Road, Thailand, malaya the NEI the PI, the Russian maritime provinces......the most essential thing now, from the United States viewpoint is to gain time. Considerable reinforcements have been rushed to the PI, but a desirable strength has not yet been reached".

This had to come as a shock to the president....his big stick in the PI was now being appraised by his own people as inadequate. I can only guess what went through his mind when told ther was inadequate strength deployed to prevent the outbreak of general warfare in the Far East.

MAGIC monitorung of the weather warning code prompted an alert radioed to all commands "NEGOTIATIONS WITH THE JAPANESE APPEAR TERMINATED .....JAPANESE FUTURE ACTIONS UNPREDICTABLEBUT HOSTILE ACTION POSSIBLE AT ANY MOMENT. IF HOSTILIES CANNOT, REPEAT, CANNOT BE AVOIDED THE UNITED STATES DESIRES THAT JAPAN COMMITS THE FIRST ACT."

Garrison commander in Hawaii Gen Short receives the alert with the additional instructions "MEASURES SHOULD BE CARRIED OUT SO AS NOT TO ALARM CIVIL POPULATION OR DISCLOSE INTENT". this additional message is interpreted as a sabotage warning . Fleet commander Kimmel also receives another specific alert "THIS DESPATCH IS TO BE CONSIDERED A WAR WARNING,. AGGRESSIVE ACTION EXPECTED BY JAPAN IN THE NEXT FEW DAYS'. Kimmels interpretation of his message is that Hawaii is under no immediate threat because the appended intell summary suggests that the targets of japanese agreesion will hit the "PI, THAILAND PENINSULA KRA ISTHMUS OR BORNEO".

In Manila, appended to Macs orders are the following instructions: "SHOULD HOSTILITIES OCCURYOU WILL CARRY OUT THE TASKS ASSIGNED IN REVISED RAINBOW 5'. Specifically this requir3ed him to conduct early air strikes and installations within tactical operating radius of the PI bases....." Mac fails ultimately to obey this order, and in fact preparation by the air forces in the PI are fitful and incomplete.


A link to the US RAINBOW 5 warplan

http://www.ibiblio.org/pha/pha/misc/rainbow5.html

November 28

PoW docks at Colombo enroute to Singapore. The Admiralty briefly considers attaching the old Light Carrier Hermes to acompany her, but rejects this on the grounds of Hermes lack of speed and endurance.

USS Enterprise departs Hawaii for Wake, carrying Marine Corps F4fs for Wake.

In Washington the President attempts to prolong the negotiations by telling Nomura "the US will continue to be patient". Meanwhile, a crisis meeting in Washington was briefed on the latest Intell. Estimates are that Japanese invasion fleets are ready to sail from Shanghai, Formosa, and Hainan, and that other Groups are already at sea. The meeting is advised "a terrific blow to all three western powers in the region is ready to fall. The President accepts the situation, and advises his staff "if either the British or the NEI are attacked by Japanese we will join them. Messages to that effect are sent at least to the British.

It is agreed to make a last ditch personal plea to the emperor.

November 29

MAGIC reveals a report from Ambassador Oshima that the germans gave gurantees to the Japanese "Should Japan become engaged in a war against the US, Germany of course would jointhe war immediately"

Curiously, Foreign Minister Togo does not seek any public announcement of this gurantee from the Germans.

In Tokyo Tojo advises his cabinet that there is now no alternative but war or "we'll lose the chance to fight"

Emperor Hirohito requests a meeting of the Jushin Council and Tojos cabinet to discuss Roosevelts offer. The Jushin Council is an advisory body of elder statesman in Japan with no legally binding weight but considerable weight just the same.


The Council includes quite a few moderates, including Prince Konoye, the Maquis Kido and Barons Okada and Wakatsuki . The Maquis had wanted the meeting with the Emperor present, so that hirohito could see the various opinions, but Tojo would not allow this, on the grounds that the Jushin had no legal status in the Japanese Government. A compromise was reached wherein after the meeting the elder stateman and Tojo would lunch with the Emperor and express their opinions. These final manouverings were important, because if the Emperor had expressed opposition to the move to war, Tojo would have been forced to back down. If the Emperor supported hm would be the best for tojo. if the Emperor was silent, Tojo could legally exercise his executive power.

The meeting began at 9:30 and and continued throughout the day. Ther was a break for the lunch with the emperor, and the meeting continued right through for the rest of the day into the evening

At the luncheon with the emperor, all but two of the Jushin Counci expressed opposition or doubt about the wisdom of going to war. The following is a summary of the main members various comments:

Wakatsuki : "the people have a strong spiritual strength"...." but we must carefully study whether we have the resources at our disposal to succeed in this task....this morning we have listed to the Government explanations, but i am still concerned"

Okada:"I too am not convinced"

Prince Konoye "I wonder if it is necessary to resort immediately to war even if the negotiations have failed to this point. I feel we can find a solution and still keep the status quo. In other words remain in the condition of gashin-shotan (to endure bitter hardship in the short term in the intersts of long term success)

Admiral Yonai: "I am not able to express a concrete opinion, since I dont have the background. But if you will forgive the slang I think that by trying to avoid the jiri-hin(slow poverty), we will succumb to the doka-hin(fast poverty, or fast death)

Two Jushin Generals, Abe and Hayashi were in favour of war.

Tojo tried to stop Wakatake from further comment, but could not. Wakatake asked the Council memebers and the emperor to think it over carefully and only support war if national survival was at stake. He did not think going to war for the sake of a concept....the greater east asia Co-properity sphere, wa worth risking the nation over.

Tojo was given the final right of reply. He stubbornly reiterated the matter had been discussed in detail at many liason conferences. He strongly advocated that there was no alternative to war at this stage. His hand picked cabinet collegues supported him, except Admiral Nagano who remained silent. Eventually and reluctantly, Nagano spoke....."The zero hour for out attack is December 8". Nagao revealed the surprise attack on Pearl at that point. This was news even to Tojo who had only been briefed to that point about the attacks and prepration in east Asia.

There followed an intense round of questions, Nagano finally revealed....grudgungly....that the attack was planned as a surprise attack. This evoked opposition from even the Government men, particularly Togo. Restrained at first, he eventually exploded, saying " the Navy plan was entirely unnacceptable, being contrary to all accepted norms and conventions. It was unthinkable for Japan to commit irresponsible acts that were hurtful to the national honour and prestige. One of the Jushin remarked that the Navy entire Japanese nation would be viewed as a bunch of drunk men on their way home from a late night drinking session.....

The meeting and the luncheon adjourned with the Emperor remaining totally silent.

November 30

In the North Pacific, the Pearl Harbour Task Force, skirting the regular shipping lanes, and folowing a benbeficially conceling weather front, proceeds to its refuelling dstination. The six carriers are arranged in three ccolumns, and are flanked by their escort. More than 200 miles ahead, their advance scouts (the three submarines of the force) press on to give warning orf any enemy or neutral vessels. There are none reported. Yamamoto had ordered the operation abandoned if the Task Group had been sighted before December 6.

Churchill cabled Roosevelt urging that the only chance of averting war was for an unequivocal American declaration "that any further agression by Japan will lead to immediate and grave consequences."

Decdember 1

The Admiralty orders the battlecruiser Repulse on passage with PoW to singaporee to divert to Darwin "to disconcert the Japanese and at the same time increase security" The Admiralty still has misgivings over the forward deployment of the two battleships with inadequate aircover.


Tokyo: Adm Nagano and his Chief of Staff Sugiyama visit the emperor. They formally advise him of the official time and date for "Xday". His majesty, without hesitation grants his approval. He knows that his previous days silence in the Jushin Council amounts to approval for the commencement of hostilities. "in for a penny, in for a pound" his assent to the navy timetable is merely maximising the chances of success for the Japanese.

However it is significant in the post war context. After the Tokyo war crimes trials, US chief prosecutor Joseph Keenan met the emperor, who told him he didnt know Pearl harbour was going to be bombed. From the avilable evidence, however (according to both John Toland and John Costello, he did knowand approve of Operation Z.

It is also well documented that he issued explicit directives to give the US due notice prior to the attack going in. Evidently he also met and discussed this with Togo that same day. I believe this is what saved him from dismissal and/or the gallows.

At 2 O'clock Sugiyama flashes a signal to Count Terauchi, the commander of the Southern Army Gp, of just two words HINODA YAMAGATA. The signal is intercepted, but not understood. It is the code word for "The date for commencing operations (HINODA) is December 8."

3.5 hours later Yamamoto sends a slightly longer communication in the new version of JN-25 to the Pearl Striking Force. It says NITAKA-YAMANOBORI - "Climb Mt Nitaka" . It means "attack as planned on December 8.

An aircraft carrying IJA Major Tsutomo crashes 50km North of Canton crashes in KMT controlled territory. It is carrying the full Operational orders and OOB for the impending attack. It sends the IJA into a panic, but in the end, nothing comes from this security lapse.


Washington: Roosevelt summons the british ambassador and informs him that US intelligence anticipates an imminent attack on Malaya and Siam. Roosevelt officially assures Halifax that in such an eventuality on any british or Dutch colonial possessions" we should all be in this together". A Poland style blank cheque of assurance to the british and the Dutch, in other words.

LCdr WJ Holmes, whose job it was in the OP-20-G unit to plot ja[ ship movements reports that the positions of the six IJN Fleet Carriers are somewhere "in Home Waters". The next day (December 2) he admits that in fact he has lost track of them. From then on, until the day of the attack, the daily situation reports are that there is "no information on the wherabouts of the carriers' positions

Pearl Harbour Strike Force With the weather finally clearing, Nagumo order the force to close up and douse all lights.