Pearl Harbor Betrayed (34 page)

R
EEVES
: There were either four or six whose whereabouts you didn't know?

R
OCHEFORT
: Yes, sir, but these we did—

R
EEVES
: Well, when did you hear of these carriers again?

R
OCHEFORT:
The 7th of December, sir.
14

Equally deaf to the presence of the six-carrier Striking Force in the mid–North Pacific was Station Negat, or Code and Signal Section, the naval code-breaking unit of OP-20-G, the Operational Intelligence Center in the sixth wing of Main Navy. There a memorandum on Japanese fleet locations, produced on 1 December, placed all ten carriers in home waters at Kure and South Kyushu.
15
So Washington was no help. Like Rochefort, Layton was concerned that some of the carriers had left their nests, but with no radio traffic from them excepting the unexplained
Akagi
–supply train blip, and with an unexpected change of call signs made by Japan on 1 December, there was nothing definite that Layton could report in his daily intelligence presentation to Admiral Kimmel. During the morning briefing of 2 December, as Layton remembered it, Kimmel responded:

“You mean to say that you are the intelligence officer of the Pacific Fleet and you don't know where the carriers are?”

“No, sir, I don't.”

He then said, “For all you know, they could be coming around Diamond Head [on Oahu], and you wouldn't know it?”

I answered, “Yes, sir, but I hope they'd have been sighted by now.”
16

Had Rochefort and his talented team of cryptanalysts at Hypo not been limited by Washington to breaking, if they could, the Japanese so-called Flag Officers Cipher—which proved month after month to be a fruitless assignment—and had they instead been tasked to penetrate the Japanese Navy's operational cipher, known as the Fleet General Purpose System, a “five-numeral” cipher that became known eventually as JN-25-B, Hawaii's knowledge of Japanese operational intentions in October, November, and December likely would have advanced into a galaxy of irresistible clues. But the authority to attack JN-25 was held tightly in Washington.

Navy cryptanalysts in Negat had acquired a commendable success rate in breaking into the Japanese diplomatic ciphers, starting with high-grade Purple and descending through J-19, J-17K6, J-18K8, J-22, then PA-K2 and LA, and they had made a start at JN-25B recoveries. “On 4 January 1941,” as one of Rochefort's traffic analysts, (later) Captain Jack S. Holtwick, Jr., remembered, “it was reported that about 2,000 values had been recovered out of 33,000 possible” in JN-25B—which was slightly more than 6 percent.
17
Captain Safford in OP-20-G stated from memory in August 1970, “By December 1st 1941, we had the code solved to a readable extent.”
18
The Philippines' Station Cast (which had moved in November to the island fortress of Corregidor), British cryptanalysts at Singapore, and the Dutch crypto unit in Java were given equal credit for the accomplishment. When, after 7 December, Hypo was at last relieved of the Flag Officers Code (which never was cracked sufficiently to provide intelligence) and given shared responsibility for JN-25B, the list of code group recoveries sent it from Washington numbered about 10 to 15 percent of the total—meaning that about 10 to 15 percent of each message broken surrendered some information, though not necessarily text.
19
The percentage did not mean that 15 percent of the intercepts could be read, or even that 15 percent of the words in a given message could be read.

It is important to recognize that
no naval operational message text in JN-25B was read by the United States prior to 7 December,
several revisionist writings to the contrary.
20
Ten to 15 percent of code groups was not sufficient to read message texts and very little usable intelligence derived from that level of penetration. Our living authority for that asseveration is Rear Admiral Donald M. “Mac” Showers, USN (Ret.), who joined the Hypo team as an ensign in February 1942 and stayed until January 1945. He crowned his career as chief of staff of the Defense Intelligence Agency. At a colloquium on Admiral Kimmel held in Washington on 7 December 1999, Showers told the audience, “If you would write a letter only using ten percent of the words in the dictionary, I challenge you to complete your task. We were not reading ten percent or fifteen percent of the text of JN-twenty-five messages in those days [prior to Pearl Harbor].”
21

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 reciprocal 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.