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The Spy Who Doomed Pearl Harbor

By Edward Savela 
Originally published by MHQ magazine. Published Online: November 08, 2011 
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Armed with intelligence supplied by spy Takeo Yoshikawa (left), Japanese pilots decimated the American fleet at Pearl Harbor in 1941. (Left: Library of Congress; Right: U.S. Navy/National Archives)
Armed with intelligence supplied by spy Takeo Yoshikawa (left), Japanese pilots decimated the American fleet at Pearl Harbor in 1941. (Left: Library of Congress; Right: U.S. Navy/National Archives)

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At 1:20 a.m. on December 7, 1941, on the darkened bridge of the Japanese aircraft carrier Akagi, Vice Admiral Chui­chi Nagumo was handed the following message: "Vessels moored in harbor: 9 battleships; 3 class B cruisers; 3 seaplane tenders, 17 destroyers. Entering harbor are 4 class B cruisers; 3 destroyers. All aircraft carriers and heavy cruisers have departed harbor….No indication of any changes in U.S. Fleet or anything unusual."

American officials could have easily found the Japanese spy who set the stage for the Pearl Harbor attack—if only they had looked

Nagumo was commanding a task force about to strike Pearl Harbor, crush the Pacific Fleet there, and open Japan's war with the United States. The message, the last of many sent from the code room at the Japanese consulate in Honolulu, was received only hours before the attack—now 70 years ago.

Astonishingly, such critical intelligence was not the work of a brilliant Japanese superspy who had worked his way into the heart of the fleet's installation. Rather, Takeo Yoshikawa, a naval officer attached to the consulate and known to the Americans, had simply watched the comings and goings of the fleet from afar, with no more access than a tourist. He made little effort to cloak his mission, and almost certainly would have been uncovered if American intelligence had been more on the ball, or if America's lawmakers had recognized the mortal threat Japan presented. Instead, he raised little suspicion, and his observations helped the Japanese piece together an extraordinarily detailed attack plan, ensuring its success.

On March 27, 1941, the following appeared in the Nippu Jiji, an English-and-Japanese-language newspaper in Honolulu: "Tadashi Morimura, newly appointed secretary of the local Japanese consulate general, arrived here this morning on the Nitta Maru from Japan. His appointment was made to expedite the work on expatriation applications and other matters." The announcement should have drawn the attention of American intelligence agents, as there was no Tadashi Morimura listed in the Japanese foreign registry. This suggested that he was new to the foreign service—or that he was something other than a diplomat.

Morimura was in fact Takeo Yoshikawa. A 1933 graduate of the Imperial Japanese Naval Academy, Yoshikawa served as a midshipman aboard the battleship Asama and the light cruiser Ura before training as a naval aviator. Promoted to ensign in July 1935, the young officer seemed well on his way to a promising career in the Imperial Navy.

About this time, however, Yoshikawa was stricken with a stomach ailment and sent home to recuperate. He felt his career was over. It's not clear whether he was ever formally discharged from active military service—an ambiguity not unusual for a military officer transitioning to spy work.

By Yoshikawa's own account, he was approached in 1936 to work as a civilian for Japan's naval intelligence service: "Since I had been studying English, I was assigned to the sections dealing with the British and American navies. I became the Japanese navy's expert on the American navy. I read everything; diplomatic reports from our attachés, secret reports from our agents around the world. I read military commentators like [New York Times military affairs editor] Hanson Baldwin. I read history too. Like the works of Mahan, the famous American admiral." Yoshikawa also studied Jane's Fighting Ships and memorized the silhouettes of all the American ships, something that would later prove critical.

In August 1940 Yoshikawa was tapped to go to Hawaii on an intelligence mission. He was ordered to keep the mission a secret, even from his peers at the Naval General Staff. Yosh­ikawa eagerly learned all he could about the Hawaiian Islands and grew his hair longer to fit in better with civilians.

His orders were to monitor the activities and movements of the American fleet in Pearl Harbor and report on the U.S. military on Oahu and the other Hawaiian Islands. But he was to be employed by the Foreign Office in Tokyo, and his connections to the navy were severed. To conceal his true identity, he was given the name Tadashi Morimura. (Throughout the 10-million word Hearings Before the Joint Committee on the Investigation of the Attack on Pearl Harbor (PHA), published in 1946, the name Takeo Yoshikawa is never mentioned, while Morimura abounds. Dr. Gordon W. Prange, who was General Douglas MacArthur's chief historian during the U.S. occupation of Japan, interviewed Yoshikawa as early as July 1950, when his identity was revealed to the Americans. But it was not until 1953, a year after the occupation ended, that Yoshikawa publicly revealed his role.)

In April 1941, Yoshikawa arrived in Hawaii and presented his credentials to Nagao Kita, Japan's consul general in Hawaii and his superior in the espionage operation. He also handed Kita six hundred-dollar bills, the cash to fund his espionage. Assigned living quarters within the consulate's compound, he assumed the title of Foreign Office chancellor. When Kita briefed Yoshikawa, "caution flowed through every sentence," according to Prange. Kita's advice, said Prange, was: "Don't make yourself conspicuous; maintain a normal, business-as-usual attitude, keep calm under all circumstances; avoid taking unnecessary risks; stay away from guarded and restricted areas and be aware of the FBI. In short, Kita reminded Yoshikawa of the Eleventh Commandment—Thou Shalt Not Get Caught."

Ever since the U.S. Pacific Fleet had permanently moved from San Diego to Pearl Harbor in May 1940, the consulate had supplied regular intelligence to Tokyo from what could be gleaned from Honolulu newspapers and casual observations. By the time Yoshikawa arrived in Hawaii, however, the plan for an attack upon the American fleet at Pearl Harbor was well under way. It was critical that the consulate increase its intelligence gathering without compromising its diplomatic cover. The inherent danger was real: Not long after Yoshikawa came to Hawaii, American authorities shut down German consulates in the United States and expelled the staffs for what they said were "activities…of an improper and unwarranted character."

Japan's spies provided precise locations of U.S. warships at Pearl Harbor, as evidenced by this diagram found on a captured Japanese midget sub after the attack. (U.S. Navy/National Archives)
Japan's spies provided precise locations of U.S. warships at Pearl Harbor, as evidenced by this diagram found on a captured Japanese midget sub after the attack. (U.S. Navy/National Archives)

Yoshikawa eagerly got to work, devoting most of each day to his clandestine mission. After carrying out the routine duties that provided his cover, he typically left the consulate around 10 a.m. and headed by bus or foot downtown. From there he hailed a taxi, and went to Aiea Heights, which had an excellent view of Pearl Harbor. Returning to the office after lunch, Yoshikawa reviewed the products of his scouting. At around 3 p.m. he changed his clothes, got another taxi, and returned to Aiea or the pier. He would then taxi up north to Wheeler Army Airfield or even farther north to the beach at Haleiwa.

Returning to the consulate, he wrote and dispatched a coded message to Tokyo, then adjourned to a teahouse for supper, relaxation, and the company of geishas. Even during this downtime, he remained vigilant. The teahouse overlooked Pearl Harbor, and he sometimes stayed all night. "I watched the searchlights from the ships in the harbor," he recalled later. "From those things I could guess what was happening out there. In the morning I could see how many ships were leaving and what direction they were taking. I watched them leave the narrow channel. How long did it take them to leave? How quickly could they leave? Then I would hurry back to the consulate and tell Tokyo."

Yoshikawa asserted he worked mostly alone. He apparently received little help from the Japanese community in Honolulu and did not break laws to obtain information. The "consulate was concerned only in 'legal' espionage" and did not attempt to enter restricted areas, the PHA concluded in 1946.

Thanks to Hawaii's large Japanese-American population, Yoshikawa easily blended in. And with its relatively open landscape, sloping elevations, and limited restrictions on movement, he readily compiled useful intelligence. His encyclopedic knowledge of U.S. ships and his methodical charting of their movements made his reports all the more valuable. Prange would conclude that his contribution to the Japanese effort was ultimately "an important one."

Ironically, the Americans could easily have uncovered this spy working in their midst. Before Yoshikawa's intelligence was sent to Tokyo, it was carefully encoded using the J-19 diplomatic code. But because there were no shortwave transmitters at the consulate, the messages were transmitted via two commercial companies, Mackay Radio and Telegraph and the Radio Corporation of America (RCA), that had offices in downtown Honolulu. The consulate's chauffeur delivered the messages to be sent.

Neither Yoshikawa nor Kita seemed concerned that outside parties were handling their sensitive information. What they did not know was that U.S. intelligence had broken the J-19 code in the summer of 1940. Sometime in 1941, an American intelligence officer sought to obtain copies of the consulate messages from Mackay and RCA. Both companies refused, citing U.S. laws that prohibited the interception of messages to and from foreign countries. Eventually, RCA yielded and agreed to surreptitiously share the communiqués.

Without the messages sent via Mackay, the Americans didn't have the whole picture. But even with the cables they did crack, authorities should have uncovered the Japanese espionage activities—and the plan to attack Pearl Harbor. On September 24, 1941, Tokyo wired the Honolulu consulate with what became known as the "bomb plot" message. It read:

#83 Strictly secret. Henceforth, we would like to have you make reports concerning vessels along the following lines insofar as possible:

1. The waters (of Pearl Harbor) are to be divided roughly into five sub-areas. (We have no objections to your abbreviating as much as you like.)
Area A. Waters between Ford Island and the Arsenal.
Area B. Waters adjacent to the Island south and west of Ford Island. (This area is on the opposite side of the Island from Area A.)
Area C. East Loch.
Area D. Middle Loch.
Area E. West Loch and the communicating water routes.

2. With regard to warships and aircraft carriers, we would like to have you report on those at anchor, (these are not so important) tied up at wharves, buoys and in docks. (Designate types and classes briefly. If possible we would like to have you make mention of the fact when there are two or more vessels along side the same wharf.)

Tokyo wanted in effect to place each American ship at Pearl Harbor in a grid. Perhaps most revealing was its final request: Why would the Japanese need to know when two or more vessels were docked side by side? This should have alerted American intelligence that Pearl Harbor might be a target, as such information would be critical in an attack; if two ships were at one wharf, dive-bombers would be needed to supplement submarine torpedoes, which likely would not be able to penetrate the outside ship's hull and still reach the ship anchored on the inside.

The Americans deciphered message 83 on October 9, two months before Pearl Harbor. But neither Rear Admiral Husband E. Kimmel, the naval commander at Pearl Harbor, nor Lieutenant General Walter C. Short, the army commander there, read it until after the attack. The U.S. War Department in Washington did not generally share intercepted messages with its field commanders, for fear that disseminating too much intelligence gleaned from Japanese cables could alert the Japanese that their code was broken. General Short later testified to Congress that he should have been informed of message 83. That dispatch "analyzed critically," he said, "is really a bombing plan for Pearl Harbor."

Admiral Kimmel agreed wholeheartedly: "No one had a greater right than I to know that Japan had carved up Pearl Harbor into sub-areas and was seeking and receiving reports as to the precise berthings in that harbor of the ships of the fleet."

As the attack drew near and Tokyo pressed him for ever more intelligence on the fleet, Yoshikawa expanded his reconnaissance, albeit through "legal" means that would not jeopardize his diplomatic status. On several occasions, playing the role of a tourist, he hired an airplane. Often accompanied by a woman, he flew near various military installations, sometimes taking photographs. He also took cruises on glass-bottom boats and evaluated alternate anchorages for ships.

Meanwhile, U.S.-Japanese relations were deteriorating. Yoshikawa was never told when Pearl Harbor would be attacked, but he felt sure his country would move in either late 1941 or early 1942.

One day in late October, Kita gave Yoshikawa a torn piece of paper and an envelope stuffed with some $14,000 in cash and instructed him to meet someone at a beach house on the eastern side of Oahu. When Yoshikawa arrived at the house, a man offered a torn piece of paper whose edges matched his own—about as close as Yoshikawa got to classic cloak-and-dagger espionage.

The man was Bernard Julius Otto Kuehn, a German national who in 1935 had been sent to Hawaii as a spy by German propaganda minister Joseph Goebbels. The Japanese intended for Kuehn to continue espionage on Oahu after the Pearl Harbor attack, when presumably Yoshikawa would have been arrested, deported, or worse. A few days after receiving Yoshikawa's payment, Kuehn gave Kita a plan that would provide intelligence after the attack to Japanese ships and submarines by signaling them with lights, fires, radio—even clothes on a line. (The message describing this plan was decrypted by American intelligence but too late; Kuehn was arrested on December 8 and later tried and convicted of espionage.)

In mid-November 1941, the Japanese liner the Taiyo Maru arrived in Honolulu carrying 340 passengers, including the youngest lieutenant commander in the Japanese Imperial Navy, Suguru Suzuki. His secret mission was to confirm information about the Pearl Harbor defenses and obtain more intelligence from Japan's sources in Honolulu.

Suzuki passed a list of 97 questions to Yoshikawa through Consul General Kita on a "tiny ball of crumpled rice paper," according to the spy. He was given 24 hours to respond. Years later, in a 1960 article, Yoshikawa recalled some of Suzuki's questions and his answers:

This is the most important question: On what day of the week would the most ships be in Pearl Harbor on normal occasions?
A: Sunday.

How many large seaplanes patrol from Pearl at dawn and sunset?
A: About 10, both times.

Where are the airports?
A: For this question, I was able to provide a map with every detail, plus aerial photos which I had taken…as late as October 21, and considerable structural detail on the hangars at Hickham and Wheeler Fields.

Are the ships fully provided with supplies and ready for sea?
A: They are not ready for combat; [they are] loaded with normal supplies and provisions only

Yoshikawa also handed over maps, sketches, and photographs for the attack. Clearly this was a goldmine for Japan. "We knew then that things were building to a climax and that my work was almost done," Yoshikawa said.

Yoshikawa's messages were sent to Tokyo, then relayed to Admiral Nagumo's Pearl Harbor task force as it steamed through the icy waters of the northern Pacific. On the evening of December 6, Yoshikawa encoded that last message detailing the U.S. fleet's numbers in Honolulu. Pearl Harbor had a very relaxed air, he said, with no barrage balloons or aircraft carriers in sight—critical information for the raid to follow.

The first bombs fell the next morning at 7:55 a.m., while Yoshikawa was having breakfast. America's Pacific fleet, completely surprised, erupted in flame. Kita and Yoshikawa rushed to the consulate and, tuning in to Radio Tokyo, heard a weather forecast that included the phrase "East wind, rain"—a prearranged signal that war against the United States was imminent. The two locked the consulate doors and began burning all their codebooks and classified material. "Smoke was pouring out of the chimney," recalled Yoshikawa.

Kita and the consulate staff were arrested at about 9:30 a.m. on December 7. It appears that the staff was confined to the consulate for about 10 days, then shipped to San Diego and on to Phoenix, where Yoshikawa was interrogated. "In the Triangle Lunch Hotel in Phoenix [Yoshikawa] was grilled every day for a week," Prange wrote, "but he assures me he did not spill the beans. He merely stated that he took excursion trips around Oahu and that was all." The United States did not have any idea of the extent of his espionage until years later.

Yoshikawa had never expected to return to Japan alive. But in August 1942, he was repatriated to Japan via the much-celebrated diplomatic prisoner exchanges of the SS Gripsholm. (The Gripsholm and another Swedish ship made 33 prisoner exchange voyages between Japan, the United States, Britain, Germany, and Italy during the war.) After arriving back in Japan, he returned to work for the intelligence division of the Naval General Staff. Then Takeo Yoshikawa faded into obscurity, his death in 1993 unremarked, his critical role in ensuring the success of the most deadly attack on American soil earning him few accolades in his defeated homeland.

 


Churchill Recruits America for His Harem

Just days after the work of Japanese spy Takeo Yoshikawa came to fruition at Pearl Harbor, Winston Churchill happily accepted an invitation to Washington to meet with President Franklin D. Roosevelt. MHQ contributor Stanley Weintraub describes the British lead-up to this war council (called the Acadia Conference) in his new book, Pearl Harbor Christmas: A World at War, 1941.

The worldwide disasters of the weekend of Pearl Harbor made it urgent for the prime minister as well as the president to pool global strategies. "As soon as I awoke," the morning after, Churchill claimed, "I decided to go over at once to see Roosevelt." He feared that the immediate impact of Pearl Harbor would be a retreat into an "America-comes-first" attitude in Washington, withholding aid to Britain and Russia while concentrating resources to strike back at Japan. In solidarity with Japan, Adolf Hitler would make that "Europe last" likelihood moot by declaring war on the United States, but isolationists who had inveighed against involvement in European wars were still influential in Congress, and the attacks on the United States had come in the Pacific. Roosevelt's cordial invitation to the White House put a new slant on everything.

Before the PM embarked on December 12, he engaged in strategy sessions with his advisers, who recommended continuing the careful language they had employed with America before the new dimension to the war.

Sir Alan Brooke, the new chief of the Imperial General Staff, recalled that Churchill turned to one in the cautious circle "with a wicked leer in his eye" and said, "Oh! That is the way we talked to her while we were wooing her; now that she is in the harem we talk to her quite differently!"

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8 Responses to “The Spy Who Doomed Pearl Harbor”


  1. 1
    Joseph Davis says:

    To Edward Savela,
    Thank you for the excellent article on Yoshikawa. I would like to point out an important omission as to the post-war activities of Yoshikawa. On December 3, 1961 Walter Cronkite aired a 25 minute clip on the CBS network, with Yoshikawa and details of his spy activities leading up to Pearl Harbor, as the featured subject. I saw this clip in that time frame, I was in High School then. If my memory is correct, and you can view the video at,
    http://www.atvaudio.com/ata_search_qs.php?current_page=2&month=&day=&year=&keywords=walter+cronkite.
    Yoshikawa, was telling the story partly in English and partly Japanese. That’s what I remember anyway.

  2. 2

    [...] operated as spies themselves. Naval Ensign Takeo Yoshikawa arrived in Hawaii in early 1941. Operating undercover, he spent his time studying and reporting on [...]

  3. 3
    Jim Finch says:

    Picture caption: "decimated". I'm not sure but I would tend to believe that 18 ships, including 8 battleships, would constitute more than "decimated".

  4. 4
    Josh says:

    If only america would have realized or took into consideration the spys that japan could have sent over, this could have turned out differently.

  5. 5

    [...] MHQ has the story of the most effective Japanese spy who reported on the comings and goings of US Navy ships at Pearl Harbour: At 1:20 a.m. on December [...]

  6. 6

    [...] The Spy Who Doomed Pearl Harbor [...]

  7. 7

    [...] on border. 1941   The Japanese fleet departs from the Kuril Islands en route to its attack on Pearl Harbor. 1947   France expels 19 Soviet citizens, charging them with intervention in internal affairs. [...]

  8. 8

    [...] planes raid Pearl Harbor, Hawaii, in a surprise attack, bringing the US into [...]



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