Takeo Yoshikawa in Honolulu

On 27 March 1941 the Japanese liner Nitta Maru entered the harbour of Honolulu on the island of Oʻahu. Among her passengers was a 29-year-old man carrying a diplomatic passport in the name of Tadashi Morimura, a new clerk at the Japanese consulate general. His real name was Takeo Yoshikawa, and he was a reserve ensign of the Imperial Japanese Navy who had been working in its intelligence service for several years. He had been sent to Honolulu with a single task: to watch, day after day, the American fleet lying a dozen or so kilometres from the city at the Pearl Harbor (PL) base, and to report to Tokyo which ships were in port, where they were moored and when they put to sea.

Yoshikawa was neither the first nor the only source of Japanese knowledge about Hawaii, but over the next eight months he became the most important. His reports, sent under the consul general’s name, reached the Naval General Staff at a time when Admiral Isoroku Yamamoto was preparing a plan to strike at that very fleet.

Who was “Tadashi Morimura”

Takeo Yoshikawa was born in 1912 in Matsuyama on the island of Shikoku, the son of a policeman. In 1933 he graduated from the Naval Academy at Etajima, served briefly in cruisers and began a specialist course, but a serious stomach illness cut his career short: in the mid-1930s he was taken off active duty, and in 1938 he was transferred to the reserve. That same year he was taken on as a civilian employee in the intelligence division of the Naval General Staff. His subject was the American navy. For nearly three years he read everything that was published about it, and he knew the silhouettes and names of American warships by heart.

Sending him to Hawaii required a cover. In 1940 Yoshikawa passed an English-language examination at the Foreign Ministry and was formally given a post as a clerk in the consular service. He was persuaded – or rather assigned – to go to Honolulu by the head of the American section of naval intelligence, Captain Bunjirō Yamaguchi. On the consulate’s staff list he appeared as a secretary; some sources, American ones in particular, call him a vice-consul. The only person at the consulate who knew his true role was the consul general, Nagao Kita, an experienced diplomat who took up the Honolulu post in the spring of 1941.

The fleet in Hawaii

Yoshikawa had come to a place that for less than a year had been the most important point on Japan’s map of the Pacific. In May 1940 President Franklin Delano Roosevelt had kept the main body of the American fleet at Pearl Harbor in order to deter Japan from an expedition southwards against the European colonies in South-East Asia. Japan was not deterred: in September it moved into northern Indochina and signed the Tripartite Pact with Germany and Italy, aimed above all at the United States. On 1 February 1941 Admiral Husband Kimmel took command of the fleet in Hawaii, which was renamed the Pacific Fleet.

At the same time a plan was taking shape in Japan of which Yoshikawa knew nothing. In January 1941 Yamamoto, commander of the Combined Fleet, presented the Navy Minister with a first outline of a carrier strike on the American fleet in its base, and in February and March his staff officers worked out the details. Such a plan required precise and up-to-date information: how many ships lay in port, on which days, at which berths, what the anti-aircraft defences and air reconnaissance around the islands looked like. Naval intelligence had been gathering this for years from the American press, from radio broadcasts, from the crews and passengers of Japanese ships calling at Honolulu, and from radio interception. What it lacked was an observer on the spot who knew about ships.

The observer in the teahouse

Yoshikawa got down to work in his first days on the island. Soon after his arrival Consul Kita took him to dinner at the Shunchō-rō, a Japanese restaurant and teahouse in the Alewa Heights above Honolulu. From the upstairs room there was a view over the whole of the Pearl Harbor lagoon, over Ford Island with its naval air station, and over the nearby Hickam army airfield. The Shunchō-rō became his favourite observation post: he went there in the evenings as a guest, in the company of geishas, and according to the recollections of the owners’ family he made use of a telescope set up in an upstairs room.

He did not stop there. He travelled round the island by taxi and in the consulate car, driven among others by Richard Kotoshirodo, a Hawaiian-born consulate clerk, and the taxi driver John Mikami. He walked the hills above the harbour, went disguised as a labourer to the sugar-cane fields at ʻAiea, from which the navy yard and the battleship moorings could be seen, and watched the harbour from the pier at Pearl City. Several times he booked a sightseeing flight over the island from John Rodgers Airport in order to view the navy and army airfields from the air. He read the local press, which printed information about ship movements. Later legends – of him diving in the harbour breathing through a reed instead of a snorkel, for example – have no basis in reliable sources.

Some 160,000 people of Japanese descent lived in Hawaii at the time, more than a third of the islands’ population. It was they whom the American military authorities feared, and the commanders on Oʻahu were preparing above all against sabotage. Yoshikawa maintained, however, that he made no use of that community. Apart from a few consulate employees and drivers, most of whom did not know the purpose of his outings, he recruited no one, and he considered the local Japanese too attached to America to be trusted. Everything he did was essentially legal: he observed what any tourist could see – only daily, methodically and with an expert’s eye.

He condensed his observations into short reports, which the consulate sent to the Foreign Ministry in Tokyo through ordinary telegraph channels as Consul Kita’s dispatches. The ministry passed them on to the Naval General Staff. The dispatches were enciphered in lower-grade consular codes (the Americans called them J-19 and PA-K2), not on the cipher machine the Americans called Purple, which was used at the most important diplomatic posts.

The dispatch of 24 September

American cryptanalysts could read these codes as well, but the Honolulu consulate’s dispatches, among hundreds of routine messages on trade and visa matters, were deciphered with a delay and given little importance. This applied too to the message that, in hindsight, proved the most telling. On 24 September 1941 Tokyo sent Honolulu dispatch No. 83, instructing that from then on reports on warships were to be divided according to five zones of Pearl Harbor: the waters between Ford Island and the Navy Yard, the waters south and west of the island, East Loch, Middle Loch, and West Loch with its channels. Warships and aircraft carriers were to be reported at anchor, at the wharves, at buoys and in dock, and it was to be noted when two or more ships were moored at the same wharf. The Americans translated this dispatch on 9 October. The officer who prepared summaries for his superiors marked it merely as “interesting”, and its contents never reached the command in Hawaii. After the war it became known as the “bomb plot message”. Admiral Kimmel testified before a congressional committee in 1946 that such information could have had no other use than planning an attack on the ships in harbour.

From mid-November Tokyo demanded reports on the ships in port twice a week, and at the end of the month even when nothing was happening. On 1 November the passenger ship Taiyō Maru arrived in Honolulu carrying naval officers disguised as members of her crew, among them Lieutenant Commander Suguru Suzuki. They brought a list of detailed questions. The answers, maps and sketches, prepared in large part by Yoshikawa, were handed over to them on board by Consul Kita before the ship sailed on 5 November. On 2 December Tokyo asked whether there were barrage balloons over Pearl Harbor and whether the ships had anti-torpedo nets. On the evening of 6 December Yoshikawa sent his last report: battleships were in port, but there were no aircraft carriers, no barrage balloons could be seen, and the battleships, in his opinion, had no anti-torpedo nets. According to Japanese sources the dispatch reached Tokyo a few hours before the attack and was passed on to Vice Admiral Chūichi Nagumo’s carrier force, which was by then approaching Hawaii.

After the attack

On the morning of 7 December Yoshikawa was having breakfast when he heard the explosions. He had not known of the attack plan to the very end; he had rather guessed at it from the questions he was being sent. Together with the consul he burned the codes and documents before police and FBI agents entered the building. The consulate staff were interned, first on the spot and later in camps on the mainland. Because no evidence was found, the Americans did not know that “Morimura” had been the chief Japanese agent in Hawaii. In August 1942 he returned to Japan in an exchange of interned diplomats. In Honolulu, by contrast, Bernard Kuehn, a German who was alleged to have passed on light signals about fleet movements for Japanese money, was convicted. His role proved marginal, and Yoshikawa maintained that he had never met him.

The congressional committee that investigated the circumstances of the attack in 1945–1946 concluded, on the basis of interrogations in Japan, that apart from the consul and his staff no agents had played any part in the attack, and that the Japanese had relied mainly on open sources. In this way, without knowing his name, it confirmed that it was precisely the work done in the consulate that had provided the most important information. Yoshikawa revealed the truth about “Morimura” himself: first in conversations with historians, then in 1960 in an article in the US Naval Institute’s journal Proceedings, and in 1963 in memoirs published in Japan.

Its place in the war

Yoshikawa’s arrival was a minor episode at a time when America was looking above all at Europe: sixteen days earlier Roosevelt had signed the Lend-Lease Act, and on 17 March the army had set up defence commands for the continental United States. Japan was simultaneously conducting talks with Washington and preparing for war. Yoshikawa was part of the latter. His work did not determine the attack on Pearl Harbor, since Yamamoto’s plan had been drawn up without him and intelligence had gathered most of the information on the fleet’s habits earlier. What it did supply was what could not be gleaned from the newspapers: a current picture of the harbour, with the disposition of the battleships, the absence of the carriers and the lack of nets in the final hours before the strike.

His reports also became one of the main threads in the post-war dispute over responsibility for the disaster of 7 December 1941: the dispatches from Honolulu had been lying translated in Washington weeks before the attack, and no one had pieced them together. For Kimmel’s defenders this was proof that he had been denied information that should have warned him; for others, an example of how hard it is, amid a flood of messages, to tell signal from noise.