On March 27, 1941, the Japanese liner Nitta Maru nuzzled against Pier 8 near Honolulu’s famous Aloha Tower on the Hawaiian island of Oahu. One of the disembarking passengers–a slim, 29-year-old man of medium height, his longish, black hair combed back–received a lei greeting from an official of the Japanese Consulate. Vice Con-sul Otojiro Okuda guided the young man, whose papers identified him as Tadashi Morimura, through customs and drove him to the two-story consulate on Nuuana Avenue.

There, Morimura chatted with Consul General Nagao Kita, was introduced to his co-workers and settled into a cottage in the consular compound. He was given the title of chancellor, which only Kita and Okuda knew would not be his real job.

In reality, the newcomer was Takeo Yoshikawa, a naval reserve ensign. Son of a policeman and a 1933 honor graduate of the Imperial Japanese Naval College, he briefly served aboard a battleship, then underwent submarine and pilot training. His promising career was truncated by a major stomach ailment. Retired after only two years, Yoshikawa was contemplating suicide when the navy offered him a job with its general staff’s intelligence division. For the next four years, the young man studied English and pored over everything available on the U.S. Navy and its Pacific Ocean bases. He was told late in 1940 that he was being posted to the American territory of Hawaii. There, posing as junior diplomat Morimura, he was to keep current on the status of the U.S. fleet and its anchorages, reporting his observations to Tokyo by coded telegraph messages. The assignment fit into a plan outlined in January 1941 by Combined Fleet Commander Isoroku Yamamoto. The plan called for an aerial assault on Hawaii as the opening move of a war that seemed inevitable as tensions rose between the United States and Japan. Yoshikawa was to become his country’s only military spy in the islands and Yamamoto’s most valuable source of current information on Oahu.

Yoshikawa began by familiarizing himself with the principal Hawaiian islands and their military installations, which were concentrated on Oahu. To explore the latter, he frequently relied on a hired cab driven by John Mikami, a Japanese-Hawaiian who often performed chores for the consulate. Other times, the spy used a 1937 Ford chauffeured by Richard Kotoshirodo, a nisei consular clerk. It did not take long for Yoshikawa to scout out the various U.S. Army and Navy bases on central, southern and eastern Oahu. Predictably, the focus of his attention was Pearl Harbor, the nearly landlocked U.S. Pacific Fleet anchorage on the south coast of the island.

When Consul General Kita introduced Yoshikawa to a Japanese-style teahouse in the mountainside Alewa Heights section, just north of downtown Honolulu, the affable intelligence officer knew it would be his favorite operational site. Not only was the teahouse strategically situated but it also fit his penchant for hard drinking and pursuing wo-men. The Shuncho ro (Spring Tide Restaurant) on Makanani Drive was run by a coopera-tive woman, a native of his own Shikoku Island, and was staffed by genial geishas. Its intelligence value lay in the view from the second floor. From the front windows, Yoshi-kawa could see Ford Island in the center of Pearl Harbor, only six miles to the west. Just to the left, adjacent to the naval installation, lay the army’s Hickam Field. The teahouse conveniently had a telescope or two that enhanced the view.

Yoshikawa wisely did not overuse any one observation post or method as he spied on activities in Pearl Harbor and Hickam airfield. Sometimes, dressed as a laborer, he took a minibus to the cane fields at Aiea to the north of the two bases. From other nearby slopes, he could look down at the submarine facilities in the harbor’s Southeast Loch. A pier at Pearl City to the northwest enabled the Japanese operative to view the far side of Ford Island and its airstrip. A close look at the harbor entrance, which might be guarded by anti-submarine nets, eluded him because both sides of the entrance were restricted areas. Without telling them what he was doing with their input, although they surely knew, he used one or more of the consulate’s personnel to complement his intelligence gathering.

In keeping with his cover, Yoshikawa avoided illegally entering military bases or stealing classified documents. He shunned cameras and notepads, relying instead on memory. Given American openness, he and his helpers got virtually all the information they needed by legal, though stealthy, means. He supplemented his observations with items of interest gleaned from daily newspapers. Furthermore, U.S. counterintelligence agencies were hampered by laws that prohibited them from probing deeply into the consulate’s communications. It was not surprising, therefore, that the Federal Bureau of Investigation and the military intelligence organizations followed leads that led elsewhere. For example, Captain Irving Mayfield, chief of the naval district intelligence offices, believed that the consulate, despite its presumed involvement in espionage, was not ‘an important part of the [Japanese spy] net. Telephone taps had provided little of value, since the consular staff assumed that the Americans were eavesdropping. Other factors that hamstrung counterintelligence operations were an American fear of alarming the population and ongoing efforts to secure the loyalty of local ethnic Japanese.

Following a time-consuming process, Yoshikawa gradually recorded the island’s patterns of military activity. Since the battleships were moored in double rows along Ford Island’s southeast side, torpedoes could be used only against the outboard ones. Most vessels were in port every weekend. Air patrols neglected the northern side of Oahu. These and other observations were written up, encoded and transmitted to Tokyo using, in turn, all the cable companies in Honolulu.

By mid-1941, although his information was not always accurate, Yoshikawa had given the Japanese navy invaluable information for its upcoming surprise attack. He knew the individual American warships by name and whether or not they were in port on a specific day. He also eliminated other sites as potential targets, enabling Yamamoto’s planners to focus on Pearl Harbor. Your concern over the old whaling port of Lahaina as a possible U.S. anchorage is groundless, the spy reported after a trip to Maui Island, to the southeast. After a glass-bottomed tourist-boat outing with two women co-workers, he described Kaneohe Bay on the windward side of Oahu’s Koolau Mountains as too shallow for major fleet units.

American reaction to the growing Axis threat began to give the Honolulu consulate anxious moments, as U.S. authorities clamped down on spies both on the mainland and in Hawaii. Local papers announced that the Honolulu police had established an espionage bureau at the request of the FBI. Less constrained than its military counterparts, the FBI also was intensifying its own look at the consulate’s 234 employees. President Franklin Roosevelt froze Japanese assets in the United States, closed American ports to Japanese ships and embargoed the sale of petroleum products to Japan. When German and Italian consulates were closed, there was concern that Japanese consulates might be next. That would have dealt a major blow to Yamamoto’s Pearl Harbor planning.

By September, Japan’s intelligence gatherers had a largely complete general picture of their Oahu targets. What they now needed were constantly updated data pinpointing warship locations, aircraft strength and the like. On September 24, Tokyo’s strictly secret message No. 83 was received at the Honolulu consulate. It requested ship locations keyed to the five geographical zones into which Japanese naval intelligence had divided the waters of Pearl Harbor. Washington codebreakers had this revealing request, known as the bomb plot message, translated within 15 days of its interception.The message was deemed noncritical by the U.S. powers-that-be, however, and was therefore not relayed to military commanders in Hawaii. Yoshikawa and his colleagues, on the other hand, now could have little doubt that their work was feeding plans to attack Pearl Harbor. The consulate’s response to the bomb plot message offered suggestions that would refine Tokyo’s request and more precisely locate individual targets. This message, too, was intercepted by the Americans–and shrugged off. By this time, Washington was downplaying Japanese subversion in the interests of ongoing diplomatic talks with Tokyo.

Yoshikawa pursued his mission with unrelenting vigor. He used numerous cover ploys to scout places that soon would gain international attention–Pearl Harbor, Hickam, Wheeler, Bellows, Kaneohe and Ewa airfields, Schofield Barracks and Fort Shafter. In October, he met the man To-kyo had selected to be his successor once the outbreak of war shuttered the consulate. Bernard Julius Otto Kuehn was a Nazi who had moved with his family to Hawaii in 1936 under contract to the Japanese. He was a sleeper, a long-term agent to be activated when needed. Kuehn was anything but an effective agent–in fact, U.S. counterintelligence already had him on its suspect list–but he was the only one available to fill in at a time when Asian faces might be unwelcome in Hawaii. The letter and package Yoshikawa gave Kuehn contained, respectively, an operational message and $14,000 in working funds. Kuehn’s vacation at Axis expense was over in more ways than one; he was arrested shortly after the Japanese attack.

In late October, the liner Taiyo Maru left Yokohama for Honolulu in a limited relaxation of the shipping freeze. Aboard were three Japanese naval officers ordered to make observations along the route laid out for the attack force, verify the consulate’s information, and obtain new data. Although other personnel maintained a brisk traffic between the consulate and the trio on the docked liner during a five-day period, Yoshikawa kept away for security reasons. Nevertheless, the brunt of the new information requirements fell on his shoulders. He worked nearly around the clock to prepare responses, which included maps covering various aspects of Oahu’s military dispositions. Despite close U.S. surveillance measures that kept them aboard ship, the visiting officers returned home satisfied that they had successfully completed their mission.

The intelligence-collecting pace paralleled the increased tension that came with a November 5 Tokyo imperial conference decision to prepare a surprise attack on Pearl Harbor for Sunday, December 7, Oahu time. Throughout the month, requests for updated information and replies flashed between Japan and Hawaii. While Yoshikawa and his helpers raced around Oahu, the Kido Butai, Japan’s attack force, assembled and steamed eastward into the North Pacific. Soon, Yoshikawa was sending biweekly ships in harbor reports to Japan for relay to the approaching task force. Late in the month, the consulate was ordered to destroy its high-level codes and all accumulated secret papers. On December 1, with Emperor Hirohito present, the Japanese Privy Council officially authorized the Pearl Harbor action. The next day, Tokyo flashed a green light to the Kido Butai to proceed with the attack.

On December 5, Yoshikawa asked cabbie Mikami to drive him west along a road that has since been replaced by the Moanalua Freeway to a point north of Pearl Harbor. From there, he watched the last of the Pacific Fleet’s three aircraft carriers put to sea with her escort of cruisers and destroyers. While the departure of USS Lexington came too late to affect Japan’s war plans, the absence of the carriers on December 7 was to have a decisive effect on America’s ability to eventually wrest the offensive from Japan. Yoshikawa was asked if the moored U.S. ships were protected by anti-aircraft balloons and anti-torpedo nets. His negative report on these contained a direct reference to a surprise attack, a slip that was caught by American codebreakers, but not translated until the day after the air raid.

At midafternoon on December 6, Yoshikawa climbed into Mikami’s taxi for what turned out to be his final reconnaissance of Pearl Harbor from the Pearl City pier. Back at the consulate, he coordinated his report with Kita, then saw that the encoded message went to the RCA communications office for transmittal to Tokyo. The Japanese foreign ministry received it shortly afterward and passed it to the navy general staff for forwarding to the attack force. According to Yoshikawa’s reporting, supplemented by coded transpacific telephone conversations with at least one other operative, everything seemed favorable for Sunday’s mission. Late that Saturday, Oahu time, the latest target information was in the hands of the Kido Butai, now churning due south toward Oahu.

The Japanese consular personnel, not having been forewarned by Tokyo, nervously gathered together as the noise of the surprise raid reached them that fateful Sunday, December 7. Kita and Okuda were dressed for a golfing date. Yoshikawa had been in his cottage. An enterprising Honolulu journalist visiting the consulate for comments provided the first confirmation of what was happening. At midday, local policemen drove past posted guards into the driveway at the rear of the consulate and took over the building. They interrupted a last-minute burning of documents. Shortly afterward, Mikami pulled up in his taxi and asked a policeman to inform the consul general and vice consul that he had arrived to drive them to the golf course. Mikami was told that his fares would not be coming out to play that day.

Yoshikawa and his colleagues remained inside their workplace for more than a week. Driven to a Coast Guard vessel, they were then transported to San Diego. In March 1942, they were placed in an Arizona camp holding numerous interned nisei. Yoshikawa later described this experience as a cruel joke. You see, I couldn’t trust them [Japanese-Americans] in Hawaii to help us. They were loyal to the United States. The spy and his companions ultimately were exchanged for American diplomats being held in Japan. During his internment, no outsider learned Yoshikawa’s true identity.

Back in his homeland, Yoshikawa married and continued working for naval intelligence until the end of the war. Fearful of arrest when U.S. troops occupied Japan in 1945, he fled into the countryside and posed as a Buddhist monk. He returned to his wife and two children after the occupation, not telling his story to an American audience until 1960. He was a bitter man, unable to earn a living and forced to rely on his wife’s insurance sales for subsistence. His government gave him neither honors nor pension. The aging Pearl Harbor spy was left to ask, Why has history cheated me?

This article was written by Wil Deac and originally appeared in the May 1997 issue of World War II magazine. For more great articles subscribe to World War II magazine today!