Codebreakers Victory (21 page)

General Mauborgne thought of Friedman's team as "the magicians" and gave the whole U.S. codebreaking operation the cover name of
Magic.
Later in the war the English code name
Ultra
began also to be applied to the U.S. program. In these pages, to avoid confusion,
Ultra
has been applied to decrypts of the Enigma and
Magic
to the success over Purple.

 

 

Tracking the Imperial Navy

 

During the 1930s the U.S. Navy employed the largest cryptologic branch among the U.S. military services. This made sense in view of the navy's responsibility to provide the first line of defense against the mounting threat of Japanese naval power. Navy leaders needed to organize the strongest effort possible to decode the signals of the Imperial Navy. But these were times when isolationist America wanted to avoid a repeat of the Great War and also when the American economy was in the grip of the Great Depression. The consequent lack of funding starved U.S. military services almost to impotency.

With its share of the inadequate defense budget the navy nevertheless built and operated a circle of radio intercept stations around the Pacific Rim and conducted a three-phase cryptologic program. One was direction finding—the use of triangulation to locate specific Japanese transmitters. The second was traffic analysis—determining from merely the sending of messages and the call signs of the senders the movements of the Japanese fleet. The third was cryptanalysis—the attempt to penetrate the content of the messages themselves. The headquarters of the cryptanalytic program was based in Washington, with outposts at Pearl Harbor and at Cavite on the island of Luzon in the Philippines.

The navy took another foresighted step. It assigned bright young officers to three-year stints in Japan, expecting them to use this duty to become familiar with the Japanese people and to develop fluency in the Japanese language.

For all the navy's prescience, however, it placed serious obstacles in the way of any career officer interested in cryptology. One was the low esteem, even contempt, in which intelligence work was generally held; time spent at it was viewed as a detour, not a step forward. Another was the encrusted rule that an officer could put in only a certain time of desk work before going on sea duty. All through the 1930s, the main source of continuity in navy cryptanalysis work was supplied by a civilian, "Miss Aggie"—Agnes Meyer Driscoll, who stayed put in Washington, did whatever codebreaking she could and trained the young officers as they came and went.

So it took a strong element of determination and grit for the navy officer to persist in pursuing code work. Fortunately for the U.S., men such as Edwin Layton, Thomas Dyer and Wesley "Ham" Wright possessed that determination and grit. So did Joseph John Rochefort.

Rochefort began his navy duties as an enlisted man and rose, by sheer ability, to head the navy's cryptographic section from 1925 to 1927. Ordinarily the navy was sending only bachelors on the three-year Japanese-learning assignment. It made an exception in Rochefort's case: in 1929, despite his being a married man with a child, he went to Japan for three years as a language student. After another half year in naval intelligence he spent the next eight years on sea duty.

In June 1941, Rochefort returned to cryptology. He was given command of the radio intelligence unit in Hawaii, to which he applied the cover name of the Combat Intelligence Unit. Within the service it became more familiarly known as Station "Hypo"—the standard name for
H
in the International Signal Code. While Rochefort's command included one hundred officers and enlisted men, the great majority were assigned to direction finding and traffic analysis. Only a small number were left over to concentrate on cryptanalysis.

A contest of wills was already forming between the cryptologic staff of the Washington naval headquarters and the staffs of the two outposts, the one known as Cast, from the C of Cavite, and Rochefort's Hypo on Oahu. The Washington operation, known as Op-20-G, wanted to maintain overall control. Its chiefs decided which Japanese codes the other two stations would be assigned to work on and which ones it would hold to itself.

Japan's navy relied not on cipher machines but on codes in the old sense: the use of codebooks in which a vocabulary of thousands of information elements such as
harbor
or
battleship
were given letter or numerical equivalents—98765, say, or 12345. The Japanese went beyond merely using the codebooks. When a message was encoded in its four- or five-number equivalents, it was subjected to a superencipherment, a further scrambling of the code numbers. The cryptanalyst faced the formidable task of stripping away this first barrier before getting at the code groups themselves.

The Japanese used a diversity of codes with varying degrees of cryptographic security. The two toughest were the "flag officers' system" and the main naval standby, which the U.S. Navy cryptologists identified as JN-25 because it was the twenty-fifth of the naval codes they had worked on. Lesser codes dealt with administrative matters, personnel changes, weather forecasts and the like.

In an unfortunate turn, as subsequent events proved, Rochefort's Hypo unit was assigned work on the flag officers' system, while only OP-20-G and Cast were responsible for trying to solve the JN-25 code. Washington also monopolized work on a lesser code, J-19, even though this was the code used by the Japanese consul in Honolulu. In another strange twist, the Cast operation in the Philippines had a Purple machine, and three were sent to the British, but the one for Hawaii was not scheduled to arrive until late December 1941.

Rear Admiral Edwin T. Layton, head of intelligence for the Hawaiian commander Admiral Husband E. Kimmel, told in his revealing memoir,
And I Was There,
how Kimmel was, in July 1941, cut out of the loop of those receiving Magic information, ostensibly for security reasons, and how his own pleas to receive Magic decrypts were rebuffed.

These quixotic assignments of responsibilities helped precipitate the coming disaster.

Rochefort and his command's efforts were wasted on the flag officers' code. Neither they nor any other Allied group ever succeeded in breaking it—partly because it was used so sparingly they never had a sufficient number of intercepts to work with. One of the most troubling what-ifs of the war was subsequently raised by Layton, Rochefort's superior: what if Rochefort, whom Layton considered the navy's most gifted performer in both linguistic and cryptanalytic terms, had been concentrating on JN-25, with which neither OP-20-G nor Cast was making serious headway? Lay-ton's answer was that if the mass of JN-25 intercepts that awaited decoding in Washington had been given to Rochefort to penetrate, the catastrophe at Pearl Harbor could have been averted. The same was true of the J-19 code. When it was eventually tackled, after the fact, its messages were found to, include highly specific exchanges between Tokyo and the Oahu consulate about U.S. warships docked at Pearl Harbor.

Even though Rochefort's team had to derive most of their intelligence from direction finding and traffic analysis, they went at their work in a manner that differed sharply from the general practices then in force on Oahu. Even in 1941, with war an increasing menace, slack peacetime ways were the rule. In many units the men were on duty only one day out of four; a commander who tried to impose a change to one day out of three met with almost an insurrection, especially on the part of the servicemen's wives. Rochefort, by contrast, aware of the Imperial Navy's ever more belligerent actions, drove himself and his men hard. As W.J. Holmes has written in
Double-Edged Secrets,
his record of those times, "Had I not witnessed it, I never would have believed that any group of men was capable of such sustained mental effort under such constant pressure for such a length of time."

With estimates based on the limited means of Sigint available to Hypo, Layton and Rochefort did their best to keep Admiral Kimmel informed about the Japanese military's plans. They could tell him with confidence that the Imperial Navy had organized a powerful force in Taiwan and Indochina. And where might this force strike? The intelligence officers' best guess was that it was poised to conquer Southeast Asia and the Netherlands East Indies.

Their estimate made sense. The English, Dutch and Americans had imposed an oil embargo on Japan. The Imperial war machine faced declining energy reserves. Japan's most likely response, the officers told Kimmel, was to seize the oil fields of the East Indies.

Layton and Rochefort were also intensely aware that the Japanese were moving southward, island jumping in their progress toward Australia. They had moved into the Marshall Islands southwest of Hawaii. The intelligence officers saw the Marshalls as the most likely base for an attack on Oahu. On their say-so, Kimmel used his inadequate air fleet to patrol more to the south and west than to the north.

The guesses by Washington ranged all over the Pacific map. The navy's chief war planner dogmatically asserted the attack would fall on the Soviet Union's easternmost provinces. Others speculated the coast of California, the Panama Canal or the Aleutian Islands, off Alaska. In a memorandum submitted to President Roosevelt ten days before the attack, Admiral Stark warned that it might fall on sites as remote as Thailand, Malaya or the Burma Road, but made no mention of Pearl Harbor. The strongest response by Washington's top brass, however, was the decision to strengthen the air fleet under the command of General Douglas MacArthur in the Philippines. A large flight of B-17 bombers was sent from the West Coast to the Philippines, with stopovers on Midway and Wake Islands. As an indication of how little anyone in power expected an attack oh Pearl Harbor, Kimmel was ordered to load half his fighter planes onto the two aircraft carriers available to him—the third was in the U.S. for an equipment refit—and deliver them to Midway and Wake. There the fighters would await the B-17s and escort them on their way to the Philippines. A smaller squadron of bombers was also to fly to Oahu.

For Layton and Rochefort, the most worrisome aspect of their reporting to Kimmel was that they could not determine with any certainty the whereabouts of Japan's aircraft carrier force. They could not know it, but they were being tricked. Fake radio traffic made the men both at Cast and Hypo believe that the carriers were in home waters. In fact, the carriers had been ordered to observe radio silence, so there was no direction finding or traffic analysis call signs to give their location away. Instead of idling close to home, the carriers, in the midst of their huge escorting fleet, were sneaking down toward Hawaii.

 

 

The Debacle at Pearl Harbor

 

The question still rankles those who lived through the experience: how, with Purple solved and three different signals intelligence units concentrating on Japanese naval codes, did the U.S. fail to anticipate Commander Isoroku Yamamoto's Hawaiian surprise that put out of action a large part of the U.S. Pacific Fleet and cost 2,403 American lives?

William Friedman himself gave the most succinct answer: "There were no messages which can be said to have disclosed exactly
where
and
when
the attack would be made"—at least not among the messages that were decrypted.

In retrospect, of course, investigators probing into the disaster found reams of evidence that
should
have awakened U.S. commands to the possibility of the assault. But the definitive proof that was necessary to pierce through lax peacetime attitudes and clouds of uncertainty never came.

Books and long Internet articles have been written supposedly "documenting" that American inaction was the deliberate result of a Franklin Roosevelt "conspiracy" to plunge the U.S. into war on the side of his friend Winston Churchill. These writers have characterized FDR as a "Communist" and a "traitor" who knew the Japanese plans but purposely avoided taking action because he wanted them to come to fruition.

Historian John Keegan has said these charges "defy logic." They fail to mention that to have achieved so malign a purpose, Roosevelt would have had to persuade the army chief of staff George Marshall and navy chief Harold Stark to go along with him. Professor Gordon W. Prange, who spent thirty-seven years researching
At Dawn We Slept,
dismissed the conspiracy charges as "an absurdity." Ronald Lewin labeled them "moonshine." In her respected work
Pearl Harbor: Warning and Decision,
Roberta Wohlstetter wrote that hostile critics of FDR "confuse his frank recognition of the
desirability
of an incident with
knowledge
of the Pearl Harbor attack." In his 2001 book,
Roosevelt's Secret War,
Joseph E. Persico reported on his research showing that on the night before Pearl Harbor, FDR actually drafted an appeal to Emperor Hirohito "to join him in a statesman-to-statesman effort to stave off disaster"—hardly the act of a leader hoping to see that disaster happen.

The sacrifice of ships and sailors at Pearl Harbor is most honestly seen as the necessary price paid for shaking off the complacency that beset the public and military alike. The Japanese timed their attack to fall on a Sunday morning because they knew full well that the American navy wanted, like everyone else, to enjoy its weekend. More ships would lie in port then than at any other time of the week, and the guard systems would be least manned.

Even so, the codebreakers came agonizingly close to ringing the alarm bells. All during 1941 the Purple decrypts kept U.S. leaders informed on the instructions Tokyo's Foreign Office was sending its embassy in Washington. To read these messages is to glimpse a group of Japanese diplomats caught between the harsh demands of the military and the unwillingness of the Americans to accede to the terms the embassy was empowered to offer. Purple told of Japan's foreign minister desperately seeking some concession from the U.S., knowing the alternative was that "a lamentable situation will occur." This sense of urgency was heightened after October 16, when the moderate government of Prince Konoe fell and was replaced by the jingoistic Tojo cabinet. On November 26 the U.S. State Department presented its conditions for resolving the negotiations. Knowing these would be unacceptable to Tojo, Tokyo's diplomats pleaded with their embassy staff to secure some crumb of a compromise; otherwise "the fate of the Empire hangs by the thread of a few days" and "things are automatically going to happen." Finally, on December 6, Tokyo warned the Washington staffers to expect a long reply to the American proposal. It came in fourteen parts, the last of which was intercepted at three a.m. on December 7. Merely rehashing the Tojo cabinet's intransigence, it ends with the ominous words that "it was impossible to reach an agreement through further negotiations." A four thirty a.m. intercept instructed the ambassador to "submit to the United States government (if possible the Secretary of State) our reply to the United States at 1:00 p.m. on the seventh, your time." And at five a.m. the final message came through, ordering the embassy to destroy its code materials.