Pearl Harbor Betrayed

by Michael Gannon

  Lack of skilled manpower was one reason why work on JN-25B advanced as slowly as it did during 1941 in OP-20-G, where effort was also being expended on attempts to gain entry to the German naval Enigma cipher used by the Atlantic U-boats. Another was the Code and Signal Section’s decision to concentrate resources on mining Japan’s diplomatic (DIP) rather than naval ciphers. It is not recorded whether that decision to go the diplomatic route was taken under pressure from outside the Navy, e.g., from Roosevelt and/or Hull, but in retrospect one may wonder if JN-25B was not the better way to go, in view of its specific operational content. DIP gave advance disclosure only to Japan’s diplomatic schemes and deadlines, not to her military intentions, although it was the source of three highly charged last-minutes messages, to be shown below, that did augur military action. A case can be made for either cipher, though certainly none can be made for the impervious Flag Officers cipher on which the talent pool at Hypo was squandered. Absent that bureaucratic miscalculation, which has less charitably been characterized as “a major blunder,”22 the Navy likely would have had in hand both JN-25 and DIP prior to Pearl Harbor.

  Rochefort was delayed in getting started on JN-25B by Op-20-G’s decision to send him its list of code recoveries by surface mail aboard a transport that experienced foul-ups at both ends of its West Coast–Honolulu passage,23 but by the end of December Hypo was going after the naval cipher at four bells.24 Less than five months later, Rochefort’s team was solving JN-25B message text in sufficient measure to be able to predict the Japanese attack on Midway in June.

  Had Rochefort been tasked to work JN-25B five months before Pearl Harbor, and had he forced it to shed its veils at the same pace as that achieved after the attack, what operational clues to Japan’s Hawaii Operation might he have captured? We have a very good idea because during the period from September 1945 through May 1946, OP-20-G’s as yet not demobilized crypanalysts, with no more war traffic to monitor, were assigned to have a look at the JN-25B intercepts acquired, but never decrypted, from the three months preceding Pearl Harbor. Altogether, 26,581 naval messages were harvested, of which 2,413 were considered “of sufficient interest for translation.” And of that number 188 were discovered to contain clues to the Pearl Harbor attack plan. These were messages exchanged during the Striking Force’s training period as well as signals transmitted from shore to the force while it steamed toward Hawaii. Many of the clues uncovered would be obscure to a layman’s eyes, e.g., the first mentions in October of “Striking Force” and “Advance Expeditionary Force,” but a trained intelligence evaluator’s eyes might well have widened at mention later that same month of “Type 91 torpedoes equipped with stabilizers” and of sixty additional torpedo technicians requested by the 1st Air Fleet for Carrier Divisions 1, 2, and 5, where the “lack of personnel is causing grave delays.”25

  Even a layman would be unlikely to miss the import of three signals dating from 1, 3, and 4 November, which read in part, “Ambush and completely destroy the U.S. enemy,” “In 3rd Special Drill in ambushing, 54 shipboard bombers will carry out bombing and strafing attack in sight of the Saeki Base,” and “Pick up and take to Kagoshima the torpedoes (total of 4) which Cardivs 1 and 2 are to fire against anchored capital ships on the morning in question.”26 (In the imagination one can see Rochefort racing from the Dungeon to Kimmel’s office.) Other intercepts from November ordered: heavy containers for storing fuel on the decks of the carriers Akagi, Soryu, and Hiryu; additional fueling hoses; an additional tanker to be assigned to the 1st Air Fleet; and, after 26 November, radio silence aboard all ships of that Combined Fleet. In yet other decrypts historians and cryptanalysts have found clues to the direction to be taken by the attacking force—a 30 November advisory to Admiral Nagumo that he might encounter Russian westbound freighters “in the northern Pacific”—and to the date for the attack: the 1208 appended twice to the “Climb Mount Niitakayama” order of 2 December.27

  Though the 188 intercept translations were completed by May 1946, when they were placed in the hands of the then CNO, Admiral Nimitz, their contents were not shared with the members of the JCC, who remained in session until July of that year. That the Navy’s cryptanalysts had attempted to acquire message text from the naval operational cipher was barely mentioned in the hearings. The “five-numbered system” or “JN-25” appears fleetingly on just five pages of the hearing’s record of its own proceedings and of all previous commissions, board, courts, and investigations. In the most extensive mention, Lt. (later Comdr.) Rudolph J. Fabian, a veteran of Cast at Corregidor, stated during the Hewitt investigation that his unit “was working on the naval system known as JN-25.… We were exchanging values [with the British unit at Singapore], both code and cipher recoveries; but we had not developed either to the point where we could read enemy intercepts.” Fabian concluded this provocative moment by acknowledging that information on the location, and movements of Japanese warships was obtained from traffic analysis and not from decryption.28 It is a curiosity that no member of the JCC, either solon or counsel, having read the Hewitt record, ever raised this question in the hearings: Were those enemy intercepts ever decrypted at a later date?

  At the Navy Department the 1945–46 translations were deep-sixed on arrival. Comdr. Baecher, whose Liaison Office was responsible for supplying the still-sitting committee with all pertinent Pearl Harbor evidence in the hands of the department, either was not apprised of the existence of the translations, or he participated in their burial. It is hard to think ill of Admiral Nimitz in this or in any other connection, but someone in his department made the decision to keep the translations away from the eyes of the committee. The cover-up prevented the JCC and the general public from knowing that, prior to Pearl Harbor, the Navy was in possession of intercepts that, if decrypted, would likely have warned the country of Japan’s impending attack. Since from 1946 until at least 1995, when the department conceded for the first time that the responsibility for Pearl Harbor “should not fall solely on the shoulders of Admiral Kimmel and General Short; it should be broadly shared [see epilogue note 50],” the department consistently deflected blame onto the shoulders of its designated scapegoats, it may well be that the forty-five-year concealment of the JN-25B translations was part of that general policy. On 20 July 1946 the department accepted without objection the JCC’s finding that Kimmel had committed “errors of judgment.” Princely self-esteem and institutional sclerosis prevented it from acknowledging misjudgments of its own.

  * * *

  On 3 December, Kido Butai rendezvoused as planned at 42 degrees north, 170 degrees west and undertook refueling of all warships, despite their rolling and pitching in heavy seas. Replenishment completed, the 2nd Supply Train, consisting of tankers Toho Maru, Toei Maru, and Nihon Maru, together with an escort destroyer, Arare, broke away from the fleet to await its return leg a short distance to the south. Toho Maru hoisted flags wishing the attackers success. Admiral Nagumo let his force know that the attack was still set for the eighth (seventh Hawaii time), that war might break out in the Far East before that date, and that so far there were no indications that their approach had been detected by the Americans.29 On that same date, to what must have been his great relief, Nagumo also had in hand intelligence that had originated at the Honolulu consulate: “So far no indications of sea patrol flights being conducted.”30 From the rendezvous position, Point C on Akagi’s chart, which was about 1,000 miles north-northwest of Oahu, the fleet hauled around onto a course that would take them southeast to the next rendezvous point, D, which was 575 nautical miles directly north of Oahu.

  On 5 December, the Striking Force sighted a passing westbound freighter “of a third nation.” That encounter, denied to have taken place by Fuchida during his postwar interrogation in October 1945, also went unmentioned in the official Japanese history of the attack, Hawai sakusen, published in 1967, although that history does recount that an alert was sent to Kido Butai that it might encounter a Soviet merchant vessel along the rec
iprocal of its route. The Japanese government later acknowledged the sighting, without identifying the vessel. It is believed to have seen either the Uzbekistan or the Azerbaidjan, which departed San Francisco for Vladivostok on 12 and 14 November, respectively.31 Yamamoto’s biographer wrote in 1979 that the task force observed the vessel “with an extraordinary degree of tension,” and stated that, had it made a radio transmission, “it would probably have found itself at the bottom of the sea within a few minutes.”32 In his account of the Pearl Harbor attack, Layton suggests that there was some prior collusion between Tokyo and Moscow on this midocean meeting, leading to the absence of any customary sighting signal in Morse from the freighter. It would have been in Moscow’s interest, he argues, for the Japanese to be consumed by a war with the United States; the force requirements of such a conflict would compel Japan to withdraw divisions from the Siberian border.33 The existence of such collusion has never been proved, however.

  * * *

  After bucketing through riled-up seas and thick weather, the Striking Force found calmer conditions as, in the early-morning hours of the sixth, it reached its next rendezvous position D, at 31 degrees north, 157 degrees west. It was a noteworthy feat of seamanship that the fleet navigator, prevented by the leaden overcast from taking sun and star sights, hit his mark by dead reckoning. There at 1130, the attack force began a final refueling before action. When completed, the 1st Supply Train, consisting of oilers Kyokuto Maru, Kenyo Maru, Kokuyo Maru, and Shinkoku Maru, together with the escort destroyer Kasumi, was dispatched from the main body to sail for home waters.34 Admiral Nagumo ordered up twenty-four knots, course due south on 180 degrees, for Kido Butai’s daring daylight dash (until twilight at 0508) over the remaining distance to Point E, 230 nautical miles north of Oahu, where the first wave of aircraft would be launched into flight. The Akagi broke out a “DG” signal flag on the masthead to signify the same message to ships that Admiral Togo Heihachiro had signaled from the flagship Mikasa thirty-six years earlier at the Battle of Tsushima Strait: THE FATE OF OUR NATION DEPENDS ON THIS BATTLE—ALL HANDS WILL EXERT THEMSELVES TO THEIR UTMOST.35 Cheering resounded on every deck. Then the crews prepared themselves for battle by prayer and by bathing for the first time since departing Tankan Bay; that is, all but the crews aboard Soryu and Hiryu, where on each carrier 550 tons of fuel oil were deck-loaded in 200-liter drums and bucket brigades were kept busy emptying their contents into the main fuel bunkers.

  Chief ordnance officer Chigusa aboard the destroyer Akigumo observed in his diary that the dash south was favored by fair winds: “The wind fortunately changed from the northwest to the north. It was now just a fair breeze of about 10 m [twenty knots]. I should feel that even God was now with us. But strong swells still remain on the surface.”36 Three submarines scouted 100 nautical miles ahead. And Akagi’s communications officer reported that normal programming on Honolulu commercial radio stations KGMB and KGU indicated that there was no sign of alarm or tension on Oahu. American patrol planes were flying, but radio bearings taken on their chatter showed that they were south of Oahu.37 From Combined Fleet intelligence came a mix of good and bad news:

  Vessels now at anchor in Pearl Harbor consist of eight battleships and two heavy cruisers.38

  … No balloons, no torpedo-defense nets deployed around battleships. No indications observed from enemy radio activity that ocean patrol flights are being made in Hawaiian area. Lexington left harbor yesterday and recovered planes. Enterprise is also thought to be operating at sea with her planes on board.39

  The Honolulu consulate agent missed picking up on the PBY dawn patrol flown each day out of Kaneohe over the operating areas to the south, as well as the 400-miles-out PBY flights to the north and northwestward of Oahu on the first, second, third, and fourth. But it was true that no patrols were being flown this Saturday over Kido Butai’s line of advance. The bad news was that neither of the Pacific Fleet’s carriers was in harbor. “It is most regrettable,” commented air operations officer Genda, “that no carriers are in.”40 Other bad news came from submarine I-72: “American Fleet is not in Lahaina Anchorage.”41 In the planning for this attack it had always been a distant hope that the Pacific Fleet would not be in Pearl Harbor, after all, but in the deep, open anchorage off Maui, where twenty-nine fathoms of water ensured that vessels sunk there would never be refloated. The near hope was realized, however: the battleships were in Pearl. As Nagumo’s chief of staff Kusaka concluded, “We may take it for granted that all eight battleships will be in the harbor tomorrow. We can’t do anything about carriers that are not there. I think we should attack Pearl Harbor tomorrow.”42 That became Nagumo’s decision.

  * * *

  Saturday the sixth was a hectic day for cryptanalists and translators at the War and Navy Departments. Traffic volume was heavy and all circuits were overloaded. At 0720 the Navy station on Bainbridge Island in Puget Sound intercepted a message from the Japanese Foreign Ministry to its Washington negotiators Nomura and Kurusu. Translated by the Army, it announced the coming, at last, of Japan’s formal answer to Secretary Hull’s uncompromising Ten-Point note of 26 November. The text, later to become known in Pearl Harbor lore as the “pilot message,” called attention to the forthcoming transmission of another “very long” memorandum, in fourteen parts:

  The situation is extremely delicate, and when you receive it I want you to please keep it secret for the time being.

  Concerning the time of presenting this memorandum to the United States, I will wire you in a separate message. However, I want you in the meantime to put it in nicely drafted form and make every preparation to present it to the Americans just as soon as you receive instructions.43

  During that day the first thirteen parts of message No. 902 came tapping over the teletype from Puget Sound in nonsequential order: parts 4, 1, 2, and 3 by 1149, parts 9 and 10, 5, 6, 7, 8, 11, 12, 13 by 1451. After decryption they required no translation since the text was in English. The content of all thirteen parts was familiar to Commander Kramer, who assembled the decrypts, since it was no more than a rehearsal of previously stated Japanese positions. Much of the language was an attempt at justifying “the China Affair.”44 What was different about it was a harsh tone in which the United States was both blamed for the failure of negotiations and imputed to have base motives. Part fourteen had not yet arrived when Kramer, with Wilkinson’s permission, personally undertook the Magic distribution. Stopping first at the White House at about 2130, he left the locked pouch with assistant naval aide Lt. Lester R. Schulz, who, accompanied by an usher, immediately carried it to President Roosevelt, who was in his second floor study with adviser and confidant Harry Hopkins.

  Just before dinner that evening, the President had dictated a radiogram to his secretary, Grace Tully. Addressed to Emperor Hirohito, one head of state to another, the message read in part: “I am confidant that both of us, for the sake of the peoples not only of our own great countries but for the sake of humanity in neighboring territories, have a sacred duty to restore traditional amity and prevent further death and destruction in the world.” As a practical matter Roosevelt offered to discuss the neutralization of Indo-China. He sent it by way of his ambassador, who had the right of audience. “Shoot this to Grew. I think can go in gray code—saves time—I don’t mind if it gets picked up.” It reached the hands of the Emperor about twenty minutes before the first bombs dropped on Pearl Harbor.45

  While Schulz stood by, Roosevelt read slowly through the somewhat turgid prose of the thirteen parts, and, after reflecting on the next-to-last paragraph with its reference to Hull’s Ten Points—“Therefore, viewed in its entirety, the Japanese government regrets that it cannot accept the proposal as a basis of negotiation”—he handed the message to Hopkins. When Hopkins finished reading the text, Roosevelt turned toward him and said, famously: “This means war.”46

  On 15 February 1946, then Commander Schulz testified about this incident before the JCC. He recalled that Hopkins, concerned that the
Japanese would attack when it was convenient for them, expressed the view that “it was too bad that we could not strike the first blow and prevent any sort of surprise.” Roosevelt nodded, but said, “No, we can’t do that. We are a democracy and a peaceful people.” Then he raised his voice and added, “But we have a good record.” Schulz went on to testify about other things that were said or not said by the two men:

  During this discussion there was no mention of Pearl Harbor.… The time at which war might begin was not discussed, but from the manner of the discussion there was no indication that tomorrow was necessarily the day. I carried that impression away because it contributed to my personal surprise when the news did come.…

  There was no mention made of sending any further warning or alert. However, having concluded this discussion about the war going to begin at the Japanese convenience, then the President said that he believed he would talk to Admiral Stark. He started to get Admiral Stark on the telephone … but I believe the White House operator told the President that Admiral Stark could be reached at the National Theater.… The President went on to state, in substance, that he would reach the admiral later, that he did not want to cause public alarm … if he [Stark] had left [the theater] suddenly.

  When questioned if anything was said about telephoning anybody else besides Stark, Schulz answered, “No, sir; there was not.”47 Stark’s biographer says that, later that night, Stark and Roosevelt discussed the Japanese message “on the private telephone line from Stark’s quarters to the White House.”48