Naval Intelligence of the United States is the oldest of all American special services, which dates back to the Office of Naval Intelligence, formed in 1882. The headquarters of US Naval intelligence (this was the name of radio intelligence) was located in the north-eastern part of Washington.

The US Navy's Communications intelligence (COMINT) operations against the Japanese Navy began in 1924, when a special unit was created under the Naval Communications Directorate, called the Research Department for conspiracy purposes. The first task of the new service was to decipher Japanese diplomatic codes, which it already had at its disposal from previous years. At first, the Navy's communications intelligence service consisted of only five people. Lieutenant L. F. Safford led the service from its very beginning and then in various periods (1924-1926, 1929-1932, and from 1936 to early 1942).

The first attempts to intercept Japanese naval communications were made in October 1927, when a communications intelligence unit under the command of Lieutenant Commander E. M. Zaharis, then serving in the intelligence service of the US Asian Fleet, equipped with special radio equipment, tracked Japanese naval exercises from the American cruiser Marblehead. Subsequently, this group, equipped with experienced radio operators, was called the Radio Division of the Pacific Fleet (RPTF).

At about the same time, the Navy began to form and deploy ground-based radio interception stations. The first such station appeared in 1925 in Beijing. Over time, radio interception stations also appeared in Shanghai, in Hiya, on the east coast of the island. Oahu, Guam, the Philippines, Bar Harbor, Maine, and Washington.

In addition to the General communications intelligence headquarters in Washington (NEGAT Station), special units designed to study Japanese radio channels and decipher messages were also stationed at Olongapo (Philippines) in 1932 (KAST Station) and at Pearl Harbor on the island of. Oahu in 1936 (HIPO station). They were supposed to provide information to the commanders of the Asian and Pacific fleets, respectively. The radio intelligence station at Pearl Harbor was commanded by Captain D. Rochefort, 3rd rank. HIPO Station was also known as the Radio Division of the Pacific Fleet. In September 1941, the Olongapo radio interception and cryptanalysis station (chief-Captain of the 3rd rank R. J. Fabian) was transferred to Corregidor Island in Manila Bay, where it was located in a spacious underground bunker.

In December 1940, the intelligence department at the headquarters of the Commander of the Fleet in Pearl Harbor was headed by E. Layton (then a Lieutenant commander). In the same post, E. Layton remained under Admiral H. E. Kimmel (1941) and Admiral of the Fleet C. W. Nimitz (1942-1945).

Kiknadze Vladimir Georgievich-Candidate of Military Sciences, captain of the 3rd rank, senior editor of the editorial office of the Military Historical Journal.

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Radio interception and analysis watches were carried out by specially trained radio operators of the US Navy and Marine Corps, who completed three-month courses in Washington. Total since 1928 Before the start of the course, 176 radio intelligence officers were trained.

Naval communications intelligence was steadily expanding and growing, reinforced by a large number of reservists called up for active service in June 1941. By December 7, it already numbered 730 people, including 75 naval officers, 645 enlisted and non-commissioned personnel, as well as 10 civilian specialists. Most of them were stationed in Washington, 186 people-in Pearl Harbor, 78-Corregidor (another 26 people were caught by the war on the way to the Philippines, after which the route was changed and people were sent to Australia) ¹ .

Before the United States entered the war, a group of cryptologists from the Army's Signal Intelligence Service (SIS), led by W. F. Friedman, developed the Purple decryption machine, which was used to open Japanese codes. Work on the creation of the machine lasted a whole year and required the greatest effort. U. Friedman called his subordinates "magicians-magicians", from which, apparently, the code name " Magic "appeared, adopted for materials decrypted using the machine "Pearl" ². However, by December 1941, only eight Purple cars had been assembled in the United States. Two were used by the War Department's intelligence service; two more were used by the Navy Department's intelligence service in Washington; and one was used by the Navy's radio intelligence station in the Philippines. The other three were sent to the British decryption center in Bletchley Park. One of the three vehicles transferred to the UK was originally intended for the US Navy's intelligence headquarters in Pearl Harbor.

The decryption services of the Army and Navy worked closely with the materials of "Perpl". Army personnel decrypted messages on even days, Navy personnel on odd days, and the results of the work were shared (later the cycles were extended to even and odd months).

Thanks to coordinated and hard work, the Americans managed to decrypt about 7 thousand Japanese diplomatic messages in the six months leading up to the attack on Pearl Harbor (i.e., about 300 documents per week). The most important of these were delivered by communications officers to a small group of high-ranking government and military figures in Washington, which included: President F. D. Roosevelt, the Secretary of State, the Secretary of War and the Secretary of the Navy, the Chief of Staff of the Army, the Chief of Naval Operations, and several other senior officers from the Army and Navy intelligence services. Each document was printed in 14 copies (12 for distribution among the above-mentioned circle of persons with an obligatory return for subsequent destruction and 2 for the archives of the army and Navy). Data from the radio intercept carried out by the Kast station was sent to the Navy codebreakers in Washington, and was also handed over to the commanders of the US forces in the Philippines, General D. MacArthur and Admiral T. C. Hart. ³

It is established that radio intelligence provided valuable intelligence about the diplomatic and intelligence activities of the Japanese, but did not reveal the plan of the Japanese attack on Pearl Harbor. So, on September 24, 1941, a radio message was intercepted in which the Japanese Foreign Minister, in response to a request from the 3rd (intelligence) office of the Japanese naval staff, asked the consulate in Honolulu to send reports of ships to Pearl Harbor using the square system. In the message, the water area of Pearl Harbor was divided into five sections. The radio message also included a request to denounce-

^{Parker F.} 1 Pearl Harbor Revisited US Navy Communication Intelligence 1924 - 1941. Washington, 1994, p. 23 - 36.

^{Richelson J. T.} 2 A century of spies. Intelligence in the twentieth century, 1995, p. 124.

^{Richelson J. T.} 3 Op. cit., p. 84 - 91.

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ti about warships and aircraft carriers at anchor, at shipyards, in the roadstead and in docks. In particular, the office wanted to know about two or more ships moored at the pier.

In early November, the Japanese introduced new call signs for active fleet formations. As a result, radio intelligence intercepted a series of emergency messages transmitted from the main Yokosuka naval base to the fleet commanders. On November 3, radio intelligence summed up its observations as follows: "Radio telegrams continue to arrive from Tokyo. Such a flood of telegrams is unprecedented. Their meaning is unclear. A simple change in call signs cannot trigger this type of activity. It is suspected that these telegrams are periodic reports of a certain nature to the high command of the Navy. " ⁴

In November 1941, special Japanese representatives K. Nomura and S. Kurusu arrived in Washington to settle strained US-Japanese relations. Thanks to radio intelligence data, the American leadership had the opportunity to get acquainted with the secret messages that K. Nomura and S. Kurusu received from Tokyo during the negotiations.

A radio message dated November 15 to the Consulate in Honolulu read: "As relations between Japan and the United States have reached a critical level, transmit your' harbor ship reports ' on an irregular basis, but at least twice a week." This is obviously the only case where the consular reports were linked to the state of relations between Japan and the United States. The message also indicated interest in current information about ships in Pearl Harbor ⁵ .

The radio message intercepted on November 19 stipulated means of notification in case Japanese relations with a number of potential adversaries reached a tipping point. The dispatch, soon decoded by American cryptanalysts, said that if Japanese-American relations were threatened, the message "Higashi no kaze ame", i.e. "East wind, rain", would be transmitted. "North wind, cloudy" will mean that Japanese-Soviet relations are under threat, "west wind, clear" - a signal of trouble in Japanese-British relations. Upon receiving this message, the recipients were required to destroy all classified materials6 .

On November 20, Japan made one last attempt to resolve the crisis in relations with the United States, offering to withdraw from Southern Indochina if the United States unfreezed Japanese assets, ensured the supply of oil and other strategic materials, and refrained from helping the Chinese who resisted Japan. Six days later, the US responded with a counter-offer: if Japan withdrew its troops from Indochina and China and joined a multilateral non-aggression pact covering East Asia, the US would unlock Japanese assets and resume trade.

On November 22, an intercepted radio message from the Ministry of Foreign Affairs, in response to requests from Nomura and Kurusu, said that the deadline for completing negotiations was extended to November 29. The message read: "No more concessions this time... it is absolutely impossible to change the deadline. After that, everything will play out automatically. " ⁷

A radio message from November 28, intercepted and translated on the same day, indicated that the negotiations were doomed to failure. In a message to Japanese representatives, it was reported that the negotiations were over. But they were instructed not to " give the impression that negotiations were interrupted." "Just say you're waiting for instructions." The dispatch of December 1 read: "To avoid creating unnecessary suspicion in the United States, we inform the press and others that while there are broad differences between Japan and the United States, negotiations are ongoing."⁸

^{Parker F.} 4 Op. cit., p. 35.

^{Drea E.} 5 MacArthurs ULTRA. Kansas, 1992, p. 53.

^{Benson R. L.} 6 A Priceless Advantage: US Navy Communication. Washington, 1997, p. 36 - 39.

^{Layton E. T.} 7 And I Was There. New York, 1985, p. 63.

⁸ Ibid., p. 65.

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Another radio message was sent on November 28 to the Consulate agent T. Yoshikawa, Hawaii. He was instructed to "report on the arrival and departure of large vessels, as well as the time they were at anchor, from the moment they entered the port until they left."⁹ T. Yoshikawa was instructed to send reports at regular intervals, even if there were no changes - apparently to make sure that none of his reports were missed. Two of these reports were decrypted on December 5.

An intercepted radio message dated December 1 indicated that Japanese attaches in London, Hong Kong, Singapore, and Manila had been ordered to stop using the encryption machines and destroy them. Another message notified the Japanese attache in Washington of the steps to be taken "when you are faced with the need to destroy the ciphers." On December 1, radio intelligence reported that the Japanese were apparently preparing some major operation. It was clearly established that the Japanese strike force was on the move. "Summing up all the information," radio intelligence reported, "we believe that a large fleet force consisting of formations of the 2nd, 3rd, and 1st fleets has left Imperial waters." ¹⁰

On December 2, 1941, a radio message from the Japanese government to its embassy in Washington was intercepted and decrypted with the following message: "867. Top secret. 1. Burn all telegraph codes available at your embassy, except for the machine codes and one copy of the "O" code and the "L" abbreviation code. 2. Immediately destroy one code machine. 3. Report on the implementation of instructions in one word "Harun". 4. Destroy all incoming and outgoing documents by any means necessary and burn all the codes that the Hosaka telegraph agency gave us. " ¹¹ The contents of this telegram were reported to the Government and the military leadership. But this did not dramatically affect the actions of the American political leadership and military command.

Nevertheless, the US Navy's radio intelligence Service took steps to strengthen the interception of Japanese communications. A round-the-clock watch was established at the radio intelligence posts.

Finally, on December 4, 1941, US Navy radio intelligence intercepted a radio message with the code "winds". The radio message indicated: "east wind, rain" and "west wind, clear" (Japan directed its aggression against the United States and England).

The former head of the covert communications department of the US Navy Intelligence Agency, Captain 2nd Rank L. Safford, described this radio message in his testimony after the war: "It was precisely to intercept this telegram that all our capabilities were mobilized. We have achieved outstanding success. This information made it possible to protect the American Pacific Fleet from a surprise attack at Pearl Harbor, that is, from such an attack as the Russians were subjected to in their time at Port Arthur. " ¹²

However, the US leadership did not respond properly to the intercepted radio message with the code "winds". No effective measures were taken to increase the combat readiness of the US armed forces in the Pacific.

While planning the attack, Japan also tried to observe international legal etiquette. To this end, the Japanese Foreign Ministry sent its Ambassador in Washington an extensive memorandum on severing diplomatic relations and declaring war on the United States-a 14-part response to Secretary Hall's counter-proposals of November 26. 13 sections of this memorandum were sent from Tokyo on December 6, 1941, and the last section was sent on December 7 at 7 a.m. with orders to the ambassador to deliver it

^{Williams J., Diskerson Y.} 9 The Invisible Criptologist. Washington, 2001, p. 72.

¹⁰ Ibid., p. 73 - 77.

¹¹ What happened at Pearl Harbor. Documents on the Japanese attack on Pearl Harbor on December 7, 1941, Moscow, 1961, p. 57.

¹² Ibid., p. 60.

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to Secretary of State C. Hall at 1 p.m., i.e. 7: 30 p.m. Hawaii time, when attacking Japanese aircraft will be on the approaches to Pearl Harbor.

The Naval radio intercept station on Bainbridge Island, Washington, intercepted every part of the Japanese memorandum as it was transmitted. From Bainbridge, it was turned over to Naval cryptanalysts in Washington. By 20: 45, the first 13 pieces had been intercepted and decrypted by the U.S. Navy's Communications Intelligence Directorate. F. D. Roosevelt understood its significance even before receiving the last piece. As soon as the first 13 pieces were delivered to the White House after 21.00, F. D. Roosevelt told the assistant Hopkins that in fact " this means war." But he still did not foresee that the likely target of a Japanese attack would be Pearl Harbor.

The fourteenth part was intercepted only after midnight on the 6th. Codebreakers in Washington soon deciphered the text of the dispatch, including its conclusion, which stated that "due to the approach of the American government, it is impossible to reach an agreement through further negotiations."

The next morning, Captain T. S. Wilkinson read the fourteenth part of the dispatch and became alarmed, believing that the consequences were "very serious" and that the message contained "warlike speeches." At about 8: 30 that morning, the head of the Far Eastern Section of Army Intelligence, R. Bratton, read this message in his office when he was handed another radio intercept material. A new radio message ordered Ambassador Nomura to transmit "our response to the United States at 1 p.m. on the seventh, your time." ¹⁴

At 9 a.m. on December 7, radio interception and decryption data were reported to the Secretary of State, the Secretary of War and the Secretary of the Navy, and at 10 a.m. to the President of the United States. However, the slowness of the leadership led to the fact that a warning telegram was sent to army headquarters, including to the Hawaiian Islands, by the War Department, which reached the Chief of Staff of the Army in Hawaii through commercial communication channels a few hours after the Japanese air raid on Pearl Harbor.

It is interesting that when the Japanese Ambassador and his adviser delivered the memorandum of their Government to the Secretary of State late at 1: 05 p.m., i.e. at 2: 05 p.m., the full text of this note, intercepted by American radio intelligence, was already on Hall's desk ^.15

Thus, despite the ability of the Americans to break the most secret diplomatic ciphers of the Japanese, the US intelligence agencies were not able to warn the leadership in a timely manner. None of the radio messages read before December 7 clearly stated that Pearl Harbor was the most likely target of an attack.

Japanese disinformation and secrecy measures also prevented US intelligence from warning of an impending attack. An aircraft Carrier Strike Force (AUS) consisting of 6 aircraft carriers (with 424 aircraft on board), 2 battleships, 2 heavy and one light cruisers, 11 destroyers, 3 submarines and 8 tankers was secretly concentrated in Hittokashgoo Bay off the island of. Etorufu, among the far northern islands, where they could not be noticed by Japanese civilians.

Through complex manipulations, the Japanese disguised the fact of purchasing warm clothing and equipment. Sailors were even banned from throwing out garbage in the waters of the Kuril Islands ¹⁶ .

Since November 10, radio communication between the ships of the AUS was prohibited, so that they would not be detected by the US Navy's radio intelligence. At the same time, disinformation radio messages were launched to give the enemy the impression that the enemy was being held responsible for the attack.

¹³ What happened at Pearl Harbor, p. 61.

^{Parker F.} 14 Op. cit, p. 36 - 38.

^{Benson R. L.} 15 A History of US Communication Intelligence during WWII. Washington, 1997, p. 78 - 81.

^{Richehon J. T.} 16 Foreign Intelligence Organizations, 1988, p. 92.

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AUS is on a training exercise off Kyushu. The radio operators of the ships, who were well known "by handwriting" by American radio intelligence, were left on the shore, at the permanent parking lots of their ships, and they conducted a false exchange of radio messages. To enhance the experience, furloughs were granted to a large number of sailors from the Yokosuka Naval District in Tokyo and Yokohama.

At midnight on December 1, the Japanese Navy changed its 20 thousand radio calls in order to further strengthen security measures. In addition, fresh intelligence reports and commands from the General Staff of the Navy to the carrier strike force were transmitted on a special frequency and were encrypted with a code that the US cryptographic services could not unravel. It was only after the war was over that it was discovered that these messages indicated plans for a surprise attack by the AUS forces and that such a unit was on its way to Hawaii at full speed. The Japanese side's intentions were also indicated by the instruction of December 2 "to ascend Mount Niitaka on December 8, I repeat, on December 8." ¹⁷ December 8 in Japan corresponded to December 7 in Hawaii. Niitaka is the highest mountain in Japan, and climbing it was then considered the height of valor in Japan. So, in an allegorical form, Admiral Yamamoto gave an order to his squadron to start a major combat operation.

The totality of intelligence data obtained on the eve of the Pearl Harbor tragedy clearly indicated that Japan was preparing an aggression against the United States. This information was supposed to encourage the transfer of the armed forces to the highest level of combat readiness. The naval base at Pearl Harbor, of course, also had to be put on alert, even if there were no concrete plans to attack it. The facts show that at least five times US intelligence data, including four times US Navy radio intelligence data, indicated increased Japanese interest in the US naval base at Pearl Harbor.

Summing up, it can be argued that US intelligence, and especially communications intelligence and US Navy codebreakers, performed their task as expected. The main reason for the tragedy that took place on December 7, 1941, was the failure of the political and military leadership of the United States to take timely measures to ensure the security of the state.

^{Williams J., Diskerson Y.} 17 Op. cit., p. 78.

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