Edited by Gerald Boerner



JerryPhoto_thumb2_thumbAs we continue our exploration of the events leading up to the December 7, 1941 attack, by air, of Pearl Harbor and shore facilities by the Japanese Navy flyers. This attack arose as a result of Japan’s need for raw resources, especially oil, and the sanctions placed upon Japan for its invasion of the China Mainland and the Indochina peninsula. Not only were preparation made on the diplomatic front, but plans were in place to simultaneously attack the United State’s military facilities on Hawaii along with the British and French holdings throughout East Asia.


During the months leading up to these coordinated attacks in December, the Japanese military had their observers gathering information about the naval movements in Pearl Harbor and aircraft resources across the Hawaiian Islands. Concurrently, a major naval task force was assembled in the Japanese home islands. This included aircraft carriers, battleships, cruisers, destroyers, and associated support vessels. This task force would launch the fighter planes, torpedo planes, and dive bombers that would rain destruction upon our naval forces anchored in the bay at Pearl Harbor. Fortunately, our aircraft carriers were on maneuvers outside of Pearl on that fateful morning.

But, I’m getting ahead of myself. This task force set sail from Japan in the latter part of November and were in position for the attack on that fateful Sunday morning. We will deal with those events in the coming days.

Now, we need to proceed with our exploration of the Japanese preparations and major players that planned this effective attack on our forces in Hawaii on December 7th… GLB

These Introductory Comments are copyrighted:
Copyright©2011 — Gerald Boerner — All Rights Reserved

[ 4207 Words ]


Quotations Related to Pearl Harbor:


“Gentlemen, we have just kicked a rabid dog.”
— Isoroku Yamamoto

“I can run wild for six months … after that, I have no expectation of success…”
— Isoroku Yamamoto

“The fate of the Empire rests on this enterprise every man must devote himself totally to the task in hand.”
— Isoroku Yamamoto

“Japanese naval officers in dress whites are frequent guests at [Pearl Harbor‘s] officers’ mess [and] are very polite. They always were. Except, of course, for that little interval there between 1941 and 1945.”
— William Manchester

“In the Pearl harbor crisis, there was a wholly American, selfless response, down to how the nurses dealt with the attack, using their stockings to dress wounds, their lipstick to mark who would live or die. Imagine that. That is what hooked me.”
— Michael Bay

“A gigantic fleet… has massed in Pearl Harbor. This fleet will be utterly crushed with one blow at the very beginning of hostilities…Heaven will bear witness to the righteousness of our struggle.”
— Rear Admiral Ito

“Anytime you look at the history of Japanese Americans and you look at all the things that have impacted our lives, there is nothing that comes anywhere close to the bombing of Pearl Harbor. That’s the watermark of our whole existence.”
— John Tateishi, president of the Japanese American Citizens League

“A military man can scarcely pride himself on having ‘smitten a sleeping enemy’; it is more a matter of shame, simply, for the one smitten. I would rather you made your appraisal after seeing what the enemy does, since it is certain that, angered and outraged, he will soon launch a determined counterattack.”
— Isoroku Yamamoto


Pearl Harbor: The Japanese Preparation for War…


Attack_on_Pearl_Harbor_Japanese_planes_viewA 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 all out war between the two 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 to estimate that 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 that Japan envisioned in the Pacific.

The Philippine islands, at that time an American territory, were also a Japanese target. The Japanese military concluded that an invasion of the Philippines would provoke an American military response. Rather than seize and fortify the islands, and wait for the inevitable US counterattack, Japan’s military leaders instead decided on the pre-emptive Pearl Harbor attack, which they assumed would negate the American forces needed for the liberation and reconquest of the islands.

Planning for the attack 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.


Pearl Harbour – the Preparation…




Hirohito, Shōwa Emperor

Hirohito_wartimeHirohito, posthumously in Japan officially called Emperor Shōwa or the Shōwa Emperor, (April 29, 1901 – January 7, 1989) was the 124th Emperor of Japan according to the traditional order, reigning from December 25, 1926, until his death in 1989. Although better known outside of Japan by his personal name Hirohito, in Japan he is now referred to exclusively by his posthumous name Emperor Shōwa. The word Shōwa is the name of the era that corresponded with the Emperor’s reign, and was made the Emperor’s own name upon his death.

At the start of his reign, Japan was already one of the great powers – the ninth largest economy in the world after Italy, the third largest naval country, and one of the five permanent members of the council of the League of Nations. He was the head of state under the limitation of the Constitution of the Empire of Japan during Japan’s imperial expansion, militarization, and involvement in World War II. After the war, he was not prosecuted for war crimes as others were. During the postwar period, he became the symbol of the new state.

Prior to World War II, Japan invaded Manchuria in 1931 and the rest of China in 1937 (the Second Sino-Japanese War). Primary sources reveal that Hirohito never really had any objection to the invasion of China in 1937, which was recommended to him by his chiefs of staff and prime minister Fumimaro Konoe. His main concern seems to have been the possibility of an attack by the Soviet Union in the north. His questions to his chief of staff, Prince Kan’in, and minister of the army, Hajime Sugiyama, were mostly about the time it could take to crush the Chinese resistance.

During World War II, ostensibly under Hirohito’s leadership, Japan formed alliances with Nazi Germany and Fascist Italy, forming the Axis Powers. In July 1939, the Emperor quarreled with one of his brothers, Prince Chichibu, who was visiting him three times a week to support the treaty, and reprimanded the army minister Seishirō Itagaki. However, after the success of the Wehrmacht in Europe, the Emperor consented to the alliance.

On September 4, 1941, the Japanese Cabinet met to consider war plans prepared by Imperial General Headquarters, and decided that:

Our Empire, for the purpose of self-defense and self-preservation, will complete preparations for war … [and is] … resolved to go to war with the United States, Great Britain, and the French if necessary. Our Empire will concurrently take all possible diplomatic measures vis-à-vis the United States and Great Britain, and thereby endeavor to obtain our objectives … In the event that there is no prospect of our demands being met by the first ten days of October through the diplomatic negotiations mentioned above, we will immediately decide to commence hostilities against the United States, Britain and the French.

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Isoroku Yamamoto, Commander-in-Chief

Isoroku_YamamotoIsoroku Yamamoto (4 April 1884 – 18 April 1943) was a Japanese Naval Marshal General and the commander-in-chief of the Combined Fleet during World War II, a graduate of the Imperial Japanese Naval Academy and a student of Harvard University (1919–1921).

Yamamoto held several important posts in the Imperial Japanese Navy, and undertook many of its changes and reorganizations, especially its development of naval aviation. He was the commander-in-chief during the decisive early years of the Pacific War and so was responsible for major battles such as Pearl Harbor and Midway. He died during an inspection tour of forward positions in the Solomon Islands when his aircraft (a Mitsubishi G4M "Betty" bomber) was shot down during an ambush by American P-38 Lightning fighter planes. His death was a major blow to Japanese military morale during World War II.

Yamamoto was promoted to Naval General (Admiral) on 15 November 1940. This in spite of the fact that when Hideki Tōjō was appointed Prime Minister on 18 October 1941, many political observers thought that Yamamoto’s career was essentially over. Tōjō had been Yamamoto’s old opponent from the time when the latter served as Japan’s deputy navy minister and Tōjō was the prime mover behind Japan’s takeover of Manchuria. It was believed that Yamamoto would be appointed to command the Yokosuka Naval Base, "a nice safe demotion with a big house and no power at all.” After the new Japanese cabinet was announced, however, Yamamoto found himself left alone in his position despite his open conflicts with Tōjō and other members of the army’s oligarchy who favored war with the European powers and America. Two of the main reasons for Yamamoto’s political survival were his immense popularity within the fleet, where he commanded the respect of his men and officers, and his close relations with the imperial family. He also had the acceptance by Japan’s naval hierarchy:

"there was no officer more competent to lead the Combined Fleet to victory than Admiral Yamamoto. His daring plan for the Pearl Harbor attack had passed through the crucible of the Japanese naval establishment, and after many expressed misgivings, his fellow admirals had realized that Yamamoto spoke no more than the truth when he said that Japan’s hope for victory in this [upcoming] war was limited by time and oil. Every sensible officer of the navy was well aware of the perennial oil problems. Also, it had to be recognized that if the enemy could seriously disturb Japanese merchant shipping, then the fleet would be endangered even more.”

Consequently, Yamamoto stayed in his post. With Tōjō now in charge of Japan’s highest political office, it became clear the army would lead the navy into a war about which Yamamoto had serious reservations. He wrote to an ultranationalist:

Should hostilities once break out between Japan and the United States, it would not be enough that we take Guam and the Philippines, nor even Hawaii and San Francisco. To make victory certain, we would have to march into Washington and dictate the terms of peace in the White House. I wonder if our politicians (who speak so lightly of a Japanese-American war) have confidence as to the final outcome and are prepared to make the necessary sacrifices.

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Prelude to Battle

Intelligence Gathering

On February 3, 1940, Yamamoto briefed Captain Kanji Ogawa of Naval Intelligence on the potential attack plan, asking him to start intelligence gathering on Pearl Harbor. Ogawa already had spies in Hawaii, including Japanese Consular officials with an intelligence remit, and he arranged for help from a German already living in Hawaii who was an Abwehr agent. None had been providing much militarily useful information. He planned to add 29-year-old Ensign Takeo Yoshikawa. By the spring of 1941, Yamamoto officially requested additional Hawaiian intelligence, and Yoshikawa boarded the liner Nitta-maru at Yokohama. He had grown his hair longer than military length, and assumed the cover name Tadashi Morimura.

YoshikawaEnsign Takeo Yoshikawa, a spy in Pearl
Harbor for Imperial Japan.

Yoshikawa began gathering intelligence in earnest by taking auto trips around the main islands, and toured Oahu in a small plane, posing as a tourist. He visited Pearl Harbor frequently, sketching the harbor and location of ships from the crest of a hill. Once, he gained access to Hickam Field in a taxi, memorizing the number of visible planes, pilots, hangars, barracks and soldiers. He was also able to discover that Sunday was the day of the week on which the largest number of ships were likely to be in harbor, that PBY patrol planes went out every morning and evening, and that there was an antisubmarine net in the mouth of the harbor. Information was returned to Japan in coded form in Consular communications, and by direct delivery to intelligence officers aboard Japanese ships calling at Hawaii by consulate staff.

In June 1941, German and Italian consulates were closed, and there were suggestions Japan’s should be closed, as well. They were not, because they continued to provide valuable information (via MAGIC) and neither President Roosevelt nor Secretary Hull wanted trouble in the Pacific. Had they been closed, however, it is possible Naval General Staff, which had opposed the attack from the outset, would have called it off, since up-to-date information on the location of the Pacific Fleet, on which Yamamoto’s plan depended, would no longer have been available.


Expecting war, and seeing an opportunity in the forward basing of the US Pacific Fleet at Hawaii, the Japanese began planning in early 1941 for an attack on Pearl Harbor. For the next several months, planning, and organizing a simultaneous attack on Pearl Harbor and invasion of British and Dutch colonies to the South occupied much of the Japanese Navy’s time and attention. The Pearl Harbor attack planning arose out of the Japanese expectation the U.S. would be inevitably drawn into the war after a Japanese attack against Malaya and Singapore.

Isoroku_YamamotoCommander-in-Chief of the Combined Fleet Fleet
Admiral Isoroku Yamamoto

The intent of a preemptive strike on Pearl Harbor was to neutralize American naval power in the Pacific, thus removing it from influencing operations against American, British, and Dutch colonies to the south. Successful attacks on colonies were judged to depend on successfully dealing with the American Pacific Fleet. Planning had long anticipated that a battle between the two Fleets would happen in Japanese home waters after the US Fleet traveled across the Pacific, under attack by submarines and other forces all the way. The US Fleet would be defeated in a climactic battle, just as had the Russian Fleet in 1905. A surprise attack posed a twofold difficulty compared to long standing expectations. First, the US Pacific Fleet was a formidable force, and would not be easy to defeat or to surprise. Second, for aerial attack, Pearl Harbor’s shallow waters made using conventional air-dropped torpedoes ineffective. On the other hand, Hawaii’s isolation meant a successful surprise attack could not be blocked or quickly countered by forces from the continental U.S.

Several Japanese naval officers had been impressed by the British Operation Judgement, in which 21 obsolete Fairey Swordfish disabled half the Regia Marina. Admiral Yamamoto even dispatched a delegation to Italy, which concluded a larger and better-supported version of Cunningham’s strike could force the U.S. Pacific Fleet to retreat to bases in California, thus giving Japan the time necessary to establish a "barrier" defense to protect Japanese control of the Dutch East Indies. The delegation returned to Japan with information about the shallow-running torpedoes Cunningham’s engineers had devised.

Japanese strategists were undoubtedly influenced by Admiral Togo’s surprise attack on the Russian Pacific Fleet at Port Arthur in 1905, and may have been influenced by U.S. Admiral Harry Yarnell’s performance in the 1932 joint Army-Navy exercises, which simulated an invasion of Hawaii. Yarnell, as commander of the attacking force, placed his carriers northwest of Oahu and simulated an air attack. The exercise’s umpires noted Yarnell’s aircraft were able to inflict serious "damage" on the defenders, who for 24 hours after the attack were unable to locate his force.

Yamamoto’s emphasis on destroying the American battleships was in keeping with the Mahanian doctrine shared by all major navies during this period, including the U.S. Navy and Royal Navy.

Minoru_GendaPlanner Commander Minoru Genda stressed
surprise would be critical.

In a letter dated January 7, 1941 Yamamoto finally delivered a rough outline of his plan to Koshiro Oikawa, then Navy Minister, from whom he also requested to be made Commander in Chief of the air fleet to attack Pearl Harbor.

A few weeks later, in yet another letter, this time directed at Takijiro Onishi—chief of staff of the Eleventh Air Fleet—Yamamoto requested Onishi study the technical feasibility of an attack against the American base.

After consulting first with Kosei Maeda, an expert on aerial torpedo warfare, and being told the harbor’s shallow waters rendered such an attack almost impossible, Onsihi summoned Commander Minoru Genda. After studying the original proposal put forth by Yamamoto, Genda agreed: "the plan is difficult but not impossible". During the following weeks, Genda expanded Yamamoto’s original plan, highlighting the importance of it being carried out early in the morning and in total secrecy, employing an aircraft carrier force and several different types of bombing.

Although attacking the US Pacific Fleet while it was at anchor in Pearl Harbor would achieve surprise, it also carried two distinct disadvantages: The targeted ships would be sunk or damaged in very shallow water, meaning that it would be quite likely that they could be salvaged and possibly returned to duty (as six of the eight battleships eventually were); and most of the crews would survive the attack, since many would be on shore leave or would be rescued from the harbor afterward. Despite these concerns, Yamamoto and Genda pressed ahead.

By April 1941, the Pearl Harbor plan became known as Operation Z, after the famous Z signal given by Admiral Tōgō at Tsushima. Over the summer, pilots trained in earnest near Kagoshima City on the Japanese island of Kyūshū. Genda had chosen it because its geography and infrastructure presented most of the same problems bombers would face at Pearl Harbor. In training, each crew flew over the 5000-foot (1500 m) mountain behind Kagoshima, dove down into the city, dodging buildings and smokestacks before dropping to an altitude of 25 feet (7 m) at the piers. Bombardiers released torpedoes at a breakwater some 300 yards (270 m) away.

Yet even skimming the water did not solve the problem of torpedoes bottoming in the shallow waters of Pearl Harbor. Japanese weapons engineers created and tested modifications allowing successful shallow water drops. The effort resulted in a heavily modified version of the Type 91 torpedo which inflicted most of the ship damage during the attack. Japanese weapons technicians also produced special armor-piercing bombs by fitting fins and release shackles to 14 and 16 inch (356 and 406 mm) naval shells. These were able to penetrate the lightly armored decks of the old battleships.

Concept of a Japanese Invasion of Hawaii

At several stages during 1941, Japan’s military leaders, including Yamamoto and Genda, gave some thought to trying to launch an invasion to seize control of the Hawaiian Islands; this would provide Japan with a strategic base to shield its new empire, deny the Americans any bases beyond the west coast of North America, further isolate Australia and New Zealand, and possibly serve as a base to facilitate attacks on the American West Coast.

Although this proposal gained some support, it was ultimately dismissed for several reasons:

  • Japan’s ground forces, logistics and resources were already fully committed, not only to the Second Sino-Japanese War but also for offensives in Southeast Asia that were planned to occur immediately almost simultaneously with the Pearl Harbor attack.
  • The Imperial Japanese Army (IJA), which insisted that it needed to focus on operations in China and the Southeast Asia, refused to supply any troops.
  • Most of the Combined Fleet’s senior officers, in particular Fleet Admiral Osami Nagano, believed that an invasion of Hawaii was too risky.

With an invasion ruled out, it was agreed that a massive carrier-based airstrike against Pearl Harbor to cripple the American Pacific Fleet would be sufficient. Japanese planners knew that Hawaii, with its strategic location in the Central Pacific, would serve as a critical base from which the United States could extend its military power against Japan; However, as before, the confidence of Japanese leaders that the conflict would be over quickly and that the United States would choose to negotiate a compromise rather than fight a long, bloody war overrode this concern.


The Strike Force


On November 26, 1941, the day the Hull note was received from United States Secretary of State Cordell Hull, which the Japanese leaders saw as an unproductive and same old proposal, the carrier battle group under the command of then Vice Admiral Chuichi Nagumo, already assembled in Hitokappu Wan in the Kurile Islands, sortied for Hawaii under strict radio silence.

ChuichiNagumoPDJapanAdmiral Chuichi Nagumo

The Kido Butai, the Combined Fleet’s main carrier force of six aircraft carriers carriers (at the time, the most powerful carrier force with the greatest concentration of air power in the history of naval warfare), embarked 359 airplanes, organized as the First Air Fleet. The carriers Akagi (flag), Kaga, Sōryū, Hiryū, and the newest, Shōkaku and Zuikaku, had 135 Mitsubishi A6M Type 0 fighters (Allied codename "Zeke", commonly called "Zero"), 171 Nakajima B5N Type 97 torpedo bombers (Allied codename "Kate"), and 108 Aichi D3A Type 99 dive bombers (Allied codename "Val") aboard. Two fast battleships, two heavy cruisers, one light cruiser, nine destroyers, and three fleet submarines provided escort and screening. In addition, the Advanced Expeditionary Force included 20 fleet and five two-man Ko-hyoteki-class midget submarines, which were to gather intelligence and sink U.S. vessels attempting to flee Pearl Harbor during or soon after the attack. It also had eight oilers for underway fueling.

The Execute Order

On December 1, 1941, after the striking force was en route, Chief of Staff Nagano gave a verbal directive to commander of the Combined Fleet Admiral Isoroku Yamamoto, informing him:

Japan has decided to open hostilities against the United States, United Kingdom, and the Netherlands early in December…Should it appear certain that Japanese-American negotiations will reach an amicable settlement prior to the commencement of hostilities, it is understood that all elements of the Combined Fleet are to be assembled and returned to their bases in accordance with separate orders. [The Kido Butai will] proceed to the Hawaiian Area with utmost secrecy and, at the outbreak of the war, will launch a resolute surprise attack on and deal a fatal blow to the enemy fleet in the Hawaiian Area. The initial air attack is scheduled at 0330 hours, X Day.

Osami_NaganoFleet Admiral Osami Nagano

Upon completion, the force was to return to Japan, re-equip, and re-deploy for "Second Phase Operations".

Finally, Order number 9, issued on 1 December 1941 by Nagano, instructed Yamamoto to crush hostile naval and air forces in Asia, the Pacific and Hawaii, promptly seize the main U.S., British, and Dutch bases in East Asia and "capture and secure the key areas of the southern regions".

On the home leg, the force was ordered to be alert for tracking and counterattacked by the Americans, and to return to the friendly base in the Marshall Islands, rather than the Home Islands.

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Pearl Harbor Was An INSIDE JOB: FDR Knew…



Please take time to further explore more about Pearl Harbor, Pearl Harbor Day of Remembrance, Events Leading to Pearl Harbor Attack, Hirohito, Shōwa Emperor, Isoroku Yamamoto, Attack on Pearl Harbor, Imperial Japanese Navy (IJN), Dutch East Indies, and the Invasion of French Indochina by accessing the Wikipedia articles referenced below. In most cases, the text in the body of this post has been selectively excerpted from the articles; footnotes and hyperlinks have been removed for readability…





Dates and events based on:

William J. Bennett and John Cribb, (2008) The American Patriot’s Almanac Daily Readings on America. (Kindle Edition)


Background information is from Wikipedia articles on:

Wikipedia: Pearl Harbor…

Wikipedia: Pearl Harbor Day of Remembrance

Wikipedia: Events Leading to Pearl Harbor Attack

Wikipedia: Hirohito, Shōwa Emperor…

Wikipedia: Isoroku Yamamoto…

Wikipedia: Attack on Pearl Harbor…

Wikipedia: Imperial Japanese Navy (IJN)…

Wikipedia: Dutch East Indies…

Wikipedia: Invasion of French Indochina…

Brainy Quote: Pearl Harbor Quotes…


Other Posts on related Topics:

Prof. Boerner’s Explorations: Revisiting the Archives — Pearl Harbor…

Prof. Boerner’s Explorations: Pearl Harbor: Background of the Surprise Attack…

Prof. Boerner’s Explorations: Pearl Harbor: Background of the Conflict…

Prof. Boerner’s Exploration: Pearl Harbor: Part 1, Background of the Conflict…

Prof. Boerner’s Exploration: Pearl Harbor: The Japanese Preparation for War…