In the years after World War II, innumerable books and articles have focused on the question of how the Japanese were able to pull off their sneak attack on Pearl Harbor. Recently, a resurgence of popular revisionist books have been gobbled up by old Roosevelt haters, some supporters of the Pearl Harbor commanders, Husband E. Kimmel and Walter S. Short, groups of the younger generation who have a great distrust in their government since Watergate, and even present-day Japanese apologists. In addition, the conservative Internet chat boards are full of such Pearl Harbor conspiracy devotees.
Common sense always has argued against the notion that such a conspiracy ever could have been organized, much less covered up, for more than a half-century. Hundreds of people would have had to be involved and kept silent. If President Roosevelt’s goal had been to shock the nation into the fight against Adolf Hitler, it was far from inevitable that war with Japan would mean war with Germany. In any case, there was hardly a need to sacrifice thousands of lives. As historian David Kahn has noted, it was the timing and the perfidy of the attack that roused the United States to action, not the loss of life. Finally, the U.S. Navy officers involved in Comint at the time have maintained there was no conspiracy, no cover-up, and no undisclosed warning of an attack on Pearl Harbor.
Most of these men are now dead and unable to defend themselves. That, and the recent opening of U.S. naval Comint records from the old Crane (Indiana) Depository, apparently have given revisionist conspiracy theorists and other revisionists a new lease on life. Comint is a highly technical field, and it is easy for the uninitiated to be misled by instant experts who have mined these new documents for scraps of data that, through misinterpretation, faulty speculation, and ignorance, might seem to support the revisionist agenda. Claims that U.S. Comint was breaking Japanese naval codes in the months leading to the Pearl Harbor attack have been debunked roundly by traditional historians using both old and new records.'
Both revisionist conspiracy theorists and just plain revisionists also have tried a new tack. They insist the U.S. Navy intercepted and obtained high frequency direction finder (HFDF) bearings (and nonexistent fixes) on radio transmissions by the Pearl Harbor strike force (Kido Butai) during its transit to Hitokappu Bay in the Kuriles and its subsequent track across the North Pacific Ocean and thus provided a forewarning of the attack. The amount of emphasis placed on the concealment of this foreknowledge seems to be the dividing line between the revisionist conspiracy theorists and just plain revisionists.
These authors have committed many technical errors based on just as many misunderstandings. Personal knowledge and several years of extensive research of U.S. Navy Comint records at the National Archives make it absolutely clear that the official reports of HFDF single line bearings cited by such authors were not bona fide radio signals from the Kido Butai. Instead, they were part of a clever Japanese program of radio deception. In fact, the records show that far from proving a plausible advance warning of the Japanese attack, these transmissions, together with a strict observance of radio silence, succeeded in misleading U.S. naval intelligence officials into believing the Japanese carriers were still in home waters.
Research by Japanese historians, fully supported by memoirs and testimony of Japanese naval officers who participated in the strike force, repeatedly has supported this conclusion.2 Admiral Isoroku Yamamoto ordered strict radio silence for all units of the Kido Butai. It was not broken until patrol aircraft from the cruisers Chikuma and Tone transmitted reconnaissance reports over Pearl Harbor and the Lahaina anchorage just prior to the actual attack.3
Numerous reports also confirm the practice of radio deception. Susumu Ishiguru, intelligence and communications officer for Carrier Division Two, stated, “Every day false communications emanated from Kyushu at the same time and on the same wavelength [probably 4963 kHz.] as during the training period. This would give eavesdroppers such as [Commander Joseph] Rochefort’s Combat Intelligence Unit [the idea] that the First Air Fleet remained in that area for routine training.4 Behind them [the Kido Butai] the ships left their regular wireless operators to carry on an apparent routine radio traffic in their own ‘fists’ or sending touch, which is distinctive as handwriting.”5
Captain Sadatoshi Tomioka said, “The Main Force in the Inland Sea and land-based air units carried out deceptive communications to indicate the carriers were training in the Kyushu area.”6 The main Japanese naval bases at Yokosuka, Kure, and Sasebo reportedly were engaged in considerable radio deception practices.7
Robert B. Stinnett’s book, Day of Deceit, greatly enlarged prior revisionist conspiracy theorist claims and, among other serious but faulty speculative charges, claimed the Japanese broke radio silence 129 times between 15 November and 6 December 1941. In fact, Admiral Yamamoto’s complete radio silence edict for the Kido Butai went into effect on 17 November.8 A subsequent book by Timothy Wilford noted many of Stinnett’s technical Comint claims and alleged that “[d]irection finding alone revealed Japanese actions in the Pacific.” He also concluded that present understanding of U.S. Navy intelligence reporting “best supports the revisionist position: careful design prevented foreknowledge from becoming forewarning.”9
Stinnett even made the absurd claim that messages sent by Imperial Naval Headquarters, Admiral Yamamoto, and shore-based commands seen only on the Tokyo Fleet broadcast or shore station transmissions were violations of “radio silence.”10 These messages were broadcast several times on multiple high and low frequencies, which was an established practice by Allied and Axis navies alike. They were meant to hide the locations of ships and commands at sea and never were considered a violation of the doctrine of radio silence. Stinnett also erroneously stated that the use of a new frequency, 16620 kHz., for the Tokyo Fleet broadcast on 5 December was employed to reach the Kido Butai carriers and “showed that Japan’s navy was refueling warships at sea.”11
On the contrary, the fact that this frequency had been used continuously on the Tokyo Fleet broadcast from at least 6 September destroys his argument.12 Stinnett does not tell his readers that the Tokyo Fleet broadcast also supported the southern and other invasion forces. He also claims the appearance of an “overload” broadcast on 32 and 12330 kHz. on 6 December was intended to support the carriers and submarines of the strike force.13 For the most part, however, this new “overload” broadcast on 32 kHz. (the transmitter actually was located near Sasebo) and 12330 kHz. serviced the southern invasion task force by repeating old messages while it was approaching its southern goals and gave no specific indication of any separate North Pacific Ocean operation.14
Stinnett makes other claims that the Japanese broke radio silence by referring to certain messages that originated in units or commands of the Kido Butai or associated forces and were relayed over the Tokyo Fleet broadcast in November 1941 while the ships were in port in Sasebo, Saeki Bay, Kure, Yokosuka, or Hitokappu Bay. But no record exists of any interception of these radio messages coming directly from these ships or the commands themselves. It is well known that while in port, Japanese naval ships (as was common with other navies) routinely filed messages with naval bases via messenger, cable, land- line, or blinker, and such filings were not a violation of radio silence.15 These messages were encrypted and were not decrypted and translated until 1945-47 using all the experience gained since the first decrypt of JN-25B in January 1942.16 Thus, their contents could not be read by U.S. intelligence at the time. And since these messages were being broadcast from fixed shore transmitters, no information could be obtained about the ships’ true locations.
Only three messages likely were filed at sea and thus by radio. One was from the tanker Shiriya (which was not a part of the Kido Butai and was scheduled only to refuel the separate Midway Neutralization Unit after the Kido Butai’s main assault on Pearl Harbor). And two transmissions came from far advanced Sixth Fleet scouting submarines reporting U.S. ship dispositions (or the lack thereof) in the Samoan and Hawaiian areas. These raw undecrypted messages seen only on fleet broadcasts gave no clue to U.S. naval intelligence personnel about the location of any of the Kido Butai units.17
Stinnett claims incorrectly that the U.S. Navy recognized all Japanese attempts at radio deception for what they were. Wilford recognizes that certain alleged transmissions by Kido Butai units apparently were radio deception, but he surmises that “these USN intercepts could not all have represented Japanese radio deception.”18
Combined, Stinnett’s and Wilford’s tabulations cite only four cases where U.S. Navy direction finder stations reported HFDF bearings on transmissions using old call signs of Kido Butai units after their departure from Hitokappu Bay on 26 November. Tokyo times were used and all bearings were from Station C on Corregidor, probably on 4963 kHz.19 Transmissions listed on the old “tactical frequency” (4963 kHz.) with no bearings were from Station H, Heeia, Oahu. By analyzing all the claimed transmissions by Kido Butai units from 13 November through 4 December 1941, however, it is clear that the bearings remained essentially the same, even though the Pearl Harbor attack force first transited from Saeki Bay, Kyushu, to Hitokappu Bay in the Kuriles and then across the North Pacific Ocean to Hawaii.
13 November, call sign 8YUNA CV Akagi bearing 026°
22 November, call sign 8YUNA Akagi bearing 028°*
22 November, call sign SAS02 CinC 1st Air Fleet bearing 040°*
23 November, call sign 1K1RA CV Zuikaku bearing 030°
24 November, call sign 8YUNA Akagi bearing 028°
26 November tactical frequency 4963 kHz., “carriers” no bearing obtained
27 November, call signs 8YUNA Akagi and 9RUSI CV Hiryu both bearing 030°
30 November “tactical frequency” 4963 kHz., Akagi [8YUNA] no bearing obtained**
30 November, call sign 8YUNA Akagi bearing 027°**
4 December, call sign 8YUNA Akagi bearing 030°***
When the above bearings are plotted (corrected by the standard mean error [SE] from Station H records), it is clear they were radio deception transmissions from the main Japanese naval bases at Sasebo (027°), Kure (030°), and Yokosuka (039°). They were not bona fide signals from Kido Butai units or commands. (See the DF Tracking Chart, pages 28-29.) For example, even Stinnett recognized that the 22 November transmissions (marked by single asterisks) from the Akagi and the commander-in-chief of the 1st Air Fleet should have had the same bearing instead of the 12° discrepancy noted if Vice Admiral Chuichi Nagumo as Commander-in-Chief 1st Fleet had been in the Akagi. In trying to overcome this obstacle to his theory, Stinnett surmised that Nagumo transited to Hitokappu Bay in the Kaga, and that it was passing Cape Inumbo at that time.20 The Kaga, however, was at Hitokappu Bay on 22 November, far westward from where the 040° bearing would indicate if it had been a valid transmission from that carrier.
Furthermore, some basic research would have revealed that Nagumo was in the Akagi—not the Kaga—during that transit, further confirming that the subject transmissions were actually radio deception signals emanating from the Sasebo and Yokosuka naval bases.21 The 27 and 30 November and the 4 December transmissions would have resulted in bearings of about 041°, 046°, and 054°, respectively, instead of 027° or 030° if they were actually from the Akagi or the Hiryu. Both Corregidor’s bearing of 027° on 8YUNA (Akagi) and the Station H, Heeia, intercept of the Akagi on 30 November (double asterisks) ties Corregidor’s radio deception bearing pointing to Sasebo to the “tactical frequency” 4963 kHz. observed by Station H and confirms the transmissions on this frequency also were radio deception activity.22
More confirmation of radio deception is noted (triple asterisks) with the continued use of the old call 8YUNA for the Akagi on 4 December after the 1 December complete call sign change. In fact, Station Cast’s report that the Akagi was located off Okinawa on 8 December after the Pearl Harbor attack was surely owing to more radio deception, this time emanating from Kure.23
Radio deception had convinced U.S. naval intelligence officials to report the Japanese carriers in “home waters,” Kure, or exercising off Kyushu.24 It also tended to keep such officials from seriously considering the possibility of such a spectacular action eastward in addition to the obvious and very large southern force moving toward Southeast Asia. The latter had been determined readily from sightings and communication patterns. The relatively small U.S. naval intelligence organizations at that time were cleverly misled and were not able to predict the almost unbelievable attack, in spite of their best efforts. The revelations advanced here put to rest revisionist charges that U.S. cryptologists tracked the Kido Butai by way of radar direction finder bearings, and they confirm there never was any advance knowledge of the Japanese plans to attack Pearl Harbor.
1. Stephen Budiansky, “Too Late for Pearl Harbor,” U.S. Naval Institute Proceedings, December 1999, pp. 47-51; John Prados, Combined Fleet Decoded (New York: Random House, 1995), pp. 158, 170, 175, 215; Peter Elphinck, Far Eastern File (London: Hodder & Stoughton, paperback 1998), p. 288; Frederick Parker, Pearl Harbor Revisited: United States Navy Communications Intelligence, 1924-1941 (Fort Meade, MD: Center for Cryptologic History, National Security Agency), p. 42.
2. Cordon Prange, Pearl Harbor: The Verdict of History (New York: Penguin Books, paperback, 1991), pp. 53-54 (Rear Admiral Ryunosuke Kusaka, Mitsuo Fuchida and [Susumo] Ishiguro); Edwin T. Layton et al., And I Was There (New York: Morrow & Co., 1985), note 15, p. 547 (Commander Genda, Lieutenant Commander Chuchi Yoshioka); Layton et al., And I Was There, p. 184 (radio silence generally); Michael Slackman, Target Pearl Harbor (Honolulu: University of Hawaii Press, 1990), p. 70, 321 note 5 (Heijiro Abe, Iyozo Fujita, Junich Goto, Hideo Maki, and Heita Matsumoto); Donald M. Goldstein and Katherine V. Dillon, The Pearl Harbor Papers: Inside the Japanese Plans (Washington: Brassy’s, 1993), pp. 186, 207 (Sadao Chigusa); Goldstein and Dillon, pp. 281-82 (study of the Pearl Harbor operations, lessons, communications).
3. Paragraph Four, Appendix to Combined Fleet Secret Order Number One, NARA RG38 CNSG Library Box 94 5750/37 at National Archives II, College Park, MD; Gordon Prange, At Dawn We Slept (New York: Penguin Books, paperback, 1982) pp. 501-2.
4. Prange, At Dawn We Slept, pp. 166-67, 338.
5. David Kahn, The Codebreakers: The Story of Secret Writing (New York: MacMillan Co., 1996) pp. 32-33.
6. Robert B. Stinnett, Day of Deceit: The Truth about FDR and Pearl Harbor (New York: The Free Press, 2000), pp. 201, 185;
7. Ladislaw Farago, The Broken Seal (New York: Random House, 1967) pp. 267-68.
8. Stinnett, Day of Deceit, pp. 162, 199, 208-9, 212; NARA RG457 SRN-11866 Archives II; See “A Cryptologic Veteran’s Analysis of ‘Day of Deceit’” by the author, Cryptologia (West Point, NY, April 2000).
9. Timothy Wilford, Pearl Harbor Redefined: USN Radio Intelligence in 1941 (Lan- ham, MD: University Press of America, 2001), pp. 48, 50-52. 71-72, 116.
10. Stinnett, Day of Deceit, pp. 199, 208-9.
11. Stinnett, Day of Deceit, pp. 183-84, 217; Wilford, Pearl Harbor Redefined, p. 52.
12. See NARA RG457 SRNs-115869, 115753, 115731, 1115435 and 115430, Archives II.
13. Stinnett, Day of Deceit, pp. 184, 217.
14. See NARA RG457 SRNs-115614, 115561, 115385, and 115377, Archives II; The Tokyo Fleet broadcast also supported the Philippines and Central Pacific invasion forces.
15. Stinnett, Day of Deceit, pp. 162-65, 208-9. See Mitsuo Fuchida and Masatake Okumiya, Midway: The Battle that Doomed Japan (London: Hutchinson, 1957), p. 104, which describes messages sent to Tokyo and Kure by the cable that linked Yamamoto’s flagship to the shore.
16. Stephen Budiansky, Battle of Wits (New York: The Free Press, 2000), pp. 8-9.
17. NARA RG457 SRN-115398 (Shiriya); SRN-115367 (1-72), both Archives II; Prange, At Dawn We Slept, p. 431 (I-/0); Stinnett, Day of Deceit, pp. 211-12, gives a slightly erroneous account of the MO’s message. Reports of messages seen on fleet broadcasts originated by RUSI8 (Akagi!), Hiei, and WAHI8 (Kido Butai submarine?) were all misidentifications. See Wilford, Pearl Harbor Redefined, pp. 72-73.
18. Stinnett, Day of Deceit, p. 202; Wilford, Pearl Harbor Redefined, pp. 69, 72-73.
19. Stinnett, Day of Deceit, pp. 154-55, 185, 195, 211-12, 216-17; Wilford, Pearl Harbor Redefined, pp. 52-53, 72-73. New call signs and a new tactical frequency were assigned to the Kido Butai. VAdm. Susumu Ishiguro, Kaigunsakusen Tsu-ushinshi (Tokyo: Supplemental Police Force, 1953), part 3, ch. 2, 2(a)(4). The old frequency, 4963 kHz., obviously was reassigned to radio deception operations.
20. Stinnett, Day of Deceit, pp. 154-55.
21. Prange, At Dawn We Slept, pp. 345-46, 350, 365.
22. Neither Stinnett nor Wilford mentions this relationship. Wilford alleges that the 30 November intercept revealed the Akagi was calling “tankers” and therefore such a transmission could not be radio deception activity. The Corregidor bearing, however, shows that the transmission probably emanated from Sasebo. Furthermore, 8YUNA was only observed calling “marus” and not “tankers” specifically. Regardless, Imperial Japanese Navy officials said the purpose of this radio deception was to mimic prior exercise activity, which included refueling exercises, to lead the U.S. Navy to believe the carriers still were exercising in home waters. Wilford, Pearl Harbor Redefined, p. 73; notes 6-9 above, NARA RG457 SRNs 115709 and 116588 Archives II; Layton et al., And 1 Was There, p. 227; and Goldstein and Dillon, The Pearl Harbor Papers, pp. 145, 209.
24. Prados, Combined Fleet Decoded, p. 190.
24. Prange, At Dawn We Slept, p. 441, note 18; Joseph Rochefort’s Comint Summaries for 1 November-6December 1941, NARA RG 38 CNSG Library Box 164, 5830/54 Archives II; Layton et al., And I Was There, pp. 186, 227-30.