Japanese intelligence in the Second World War: Operation Z

(To Francesco Sisto)
11/03/21

The attack on Pearl Harbor on December 7, 1941 can be considered, to all intents and purposes, one of the greatest intelligence operations that took place during the Second World War. This attack went down in history as Operation Z.

At Pearl Harbor the budget was very hard for the United States: the Pacific fleet - especially the battleships - was severely damaged and the air forces were, in fact, annihilated.

The battleships Arizona e Oklahoma, the minelayer Oglala and the target ship Utah sank. Other battleships such as the California, West Virginia , Nevada they were badly damaged and rested on the bottom. The Maryland, Tennessee e Pennsylvania they were seriously hit, “like the cruisers Helena, Raleigh e Honoluluof destroyers Cassini, Downes e Shaw and auxiliary vessels Vestal e Curtiss"1. In addition, the Japanese destroyed and damaged more than 300 US aircraft.

The human losses were enormous: almost 2.500 victims and about 2.000 injured. The attack on Pearl Harbor was a severe "blow" to the American nation.

On December 8, 1941, in Washington, United States President Roosevelt said in the hall of Congress: "Yesterday, December 7, 1941, a date that will remain engraved in infamy, the United States of America was suddenly and deliberately attacked by the air and naval forces of the Empire of Japan".

Thus on December 7, 1941, from that moment on, he obtained the historical definition of "Day of Infamy", and throughout the Second World War the Americans would "find the courage to fight hard in the motto: Remember Dec. 7th! "2.

The attack plan against Pearl Harbor was commissioned by Admiral Yamamoto Isoroku, commander in the field of the Japanese imperial naval forces.

In 1941 the chances of war between Japan and the United States were very high, and Admiral Yamamoto was convinced that the only possibility of prevailing against the American war-industrial power was to strike immediately and with all possible force the US Pacific fleet anchored in Pearl Harbor. According to the Japanese strategist, all this would have had the consequence of forcing the United States to negotiate with the Empire of the Rising Sun to reach a compromise between the two nations in the Pacific.

The preparations of theOperation Z and, finally, its extraordinary success was - in large part - due to the Japanese secret service, kempei, and to the intelligence services of the imperial navy, the Joho Kyoku; in addition to the information and support networks present on the ground: the Honolulu spies.

The tasks and objectives of the island's spies were numerous: to ensure the solidity of the coastal defenses and to advise the best point for attack; decide the day and time for the bombing; "Guide the attack itself with clandestine radios and accurately identify all the enemy's losses"3, in such a way that the Japanese imperial staff could regulate and organize itself in subsequent war moves.

It should be remembered that not only Japanese but also German agents took part in these delicate and risky tasks; In this way, a real team of spies was created. Among these was one who played a role of primary importance for the mission: the young twenty-eight year old Takeo Yoshikawa.

Yoshikawa was born on the island of Shikoku, attended the naval academy of Etajima and then left it in 1936. He later took leave of the navy for health reasons, and went to the Ministry of Foreign Affairs.

During his career he carried out undercover missions in Hong Kong and Shanghai, where he achieved excellent results. In Honolulu he demonstrated all his skills as a spy (not surprisingly he was considered one of the best agents of the naval intelligence service).

On March 20, 1941, Yoshikawa (photo) left Yokohama for Honolulu with the post of trainee vice consul officer (the cover name was Morimura Tadachi), and with the task of studying the legal situation of children born in Hawaii to Japanese parents. . Once disembarked, Vice Consul Morimura immediately reached the Japanese consulate and immediately set to work. It should be emphasized that the same consul general Kita Nagao was a secret agent of the Joho Kyoku.

During his "stay" on the island the young Yoshikawa made numerous reconnaissance in order to have a picture of the situation, and tried to locate all the US military defenses. In addition, the Japanese spy, to make his coverage even more solid, had a relationship with a local girl of Japanese origin, and at the same time began to collect all the tourist postcards available and send them with greetings to his "friends" in Japan. . These postcards proved to be very useful as they "allowed him to locate a considerable number of military targets"4 in extreme tranquility.

Interestingly, it was only after the end of the conflict that the Americans realized, with disbelief (to put it mildly), that one of the secret weapons of espionage used in Pearl Harbor was just plain tourist postcards. In fact, through the color images the cartographers of the Empire of the Rising Sun were able to reconstruct an accurate topography of the islands, and in doing so they gave the opportunity to the aviation squadrons to study, in detail, the points considered the best for the attack.

The port of Pearl Harbor, with the passage of time, became the control target of the spy Yoshikawa (who hired various coverages to investigate: fisherman, painter, simple tourist).

Meanwhile, the Japanese had decided: Pearl Harbor would be the main attack on the US Pacific fleet.

As previously reported, the Japanese intelligence services could also count on other agents present in Hawaii and among these there was an unsuspected German "little family": the Kuehns. The head of the family was Otto Kuehn, he moved with his family a few years earlier to Honolulu. Strong supporters of Nazism, they were on the payroll of the Japanese intelligence service in agreement with the German ones. Suffice it to say that since they moved to Hawaii they have received more than a hundred thousand dollars. To the locals, it was an ordinary European family; in 1939 they moved to Pearl Harbor, where they managed to rent a cottage above the harbor bay.

Yoshikawa came into contact with Otto Kuehn (photo) in October 1941: the two men agreed on putting into operation a radio transmitter that would be back - very useful - to emit the signals that would then lead the Japanese planes to the moment of the operation against the port of Pearl Harbor.

Meanwhile, in Japan, Admiral Yamamoto put his closest and most trusted collaborators to work to study and prepare theOperation Z. Among them were Kanji Ogawa, head of the American section of the naval intelligence service, Vice Admiral Onishi Takejiro, chief of staff of the second naval team, and Lieutenant Commander Genda Minoru, skilled air force pilot of the Japanese Imperial Navy. . After the war, Genda was invited to various American military academies “to lecture on the technique of the successful Pearl Harbor ambush"5.

Thanks to Vice Admiral Onishi and Captain Genda it was possible to give shape to a plan of attack, subsequently the plan was approved by the top management of the Navy.

The requests to the Japanese spies in Hawaii, therefore, became more and more pressing and precise; it was essential to have as much information as possible. For example, Captain Genda, thanks to the communications that were provided to him, noticed that the way into the sky of Pearl Harbor could be the pass of Kolekole (a narrow access located between the high volcanic mountains). It was the aerial gateway to the port of Pearl Harbor less controlled by coastal defenses.

In November, two agents of the Joho Kyoku, Maejima Toshihide and Suzuki Takao, boarded the Japanese liner Taiyo-maru, arrived in Honolulu. For a long way the Japanese ship followed the route that would have been covered in radio silence by the fleet of Vice-Admiral Nagumo (who aboard the aircraft carrier Akagi would lead the expedition). The mission of the two agents was to deliver a 97-point questionnaire to Consul Kita and Yoshikawa, useful for the final preparation of the operation. Among the questions

of the questionnaire there was: "On which day of the week are the largest number of naval units in Pearl Harbor?". The answer was "Sunday", and so it was decided that the attack would take place on Sunday 7 December 1941.

When Taiyo-maru departed from Honolulu on November 5, Maejima and Suzuki had managed to set up a perfect and detailed report that would later form the operational platform of one of the most important intelligence operations of the Second World War.

November 25 aboard the aircraft carrier Akagi, the lieutenant captain Genda gave the vessel captain Fuchida Mitsuo and his airmen all possible information about the targets to be attacked and about the conformation of the island of Oahu. L'Operation Z it was ready.

On November 26, the fleet of Vice Admiral Nagumo set sail from the island of Etorofu (today Iturup) for Pearl Harbor.

On the evening of December 5, Tokyo received the last radio message (in code) from Yoshikawa; the message read: “The battleships Oklahoma and Texas entered the harbor after three days of cruising. The Lexington and five heavy cruisers left this morning. Total ships in port: 8 battleships, 3 heavy cruisers, 15 torpedo boats, 4 light cruisers and 5 fighters. Battleships have no torpedo nets. No area observations around Hawaii. The Enterprise will sail tonight. Utah and a seaplane rescue ship entered the harbor. There are therefore nine battleships. Quiet atmosphere. All the lights on. Normal sentinels. Ground crew ". At the time of the attack the aircraft carriers would have missed the call.

On the evening of December 6, Vice Admiral Nagumo, who arrived with the aircraft carriers at the level of the island of Oahu, gave the order to raise the flagpole of theAkagi the Z flag, exactly the same that Admiral Togo Heihachiro had used in the battle of Tsushima against the Russian imperial navy in 1905. Pearl Harbor, the next morning, would have a rude awakening: theOperation Z.

At dawn on December 7, 1941, US coastal defense listening devices began to signal a squadron of planes coming from the sea. When the US military intercepted signals coming from the Kolehole Gorge, where planes generally did not pass, they felt that the receiving machines were not working at their best. In fact, they did not immediately give the alarm but they were wrong. It was almost 8,00 in the morning when the bombing of the port of Pearl Harbor began; the attack ended almost two hours later: around 9,45am.

At that time, both the Kuehn and Yoshikawa families were discovered by the FBI.

The Americans were completely taken aback. From the Empire of the Rising Sun there were shouts of joy for the brilliantly accomplished operation. According to Japanese strategists, the United States could hardly have recovered from such a military defeat.

The person who was most cautious after the Pearl Harbor attack was the one who came up with the plan: Admiral Yamamoto. The Japanese admiral, in fact, pointed out that the American aircraft carriers were not destroyed, and above all he knew very well of the war-industrial superiority that the American nation had at its disposal.

The success of theOperation Z; shortly thereafter, the spy network (which no one had noticed) that caused the Pearl Harbor catastrophe began to come to light.

1 B. Millot, The Pacific War 1941-1945. The greatest air-naval conflict in history, BUR, Milan, 2018, p. 62.

2 B. Palmiro Boschesi, The great secret battles of World War II, Mondadori, Milan, 1973, p. 88.

3 G. Fattori, Operation Tora, in Illustrated History, n. 144, 1969, p. 133.

4 B. Palmiro Boschesi, op. cit., p. 89.

5 G. Factors, op. cit., p. 132.

Photo: United States National Archives / web / USNI / FBI / US Navy