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Battle of Wits: The Complete Story of Codebreaking in World War II

Battle of Wits: The Complete Story of Codebreaking in World War II

by Stephen Budiansky


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A million pages of new World War II codebreaking records have been released by the U.S. Army and Navy and the British government over the last five years. Now, Battle of Wits presents the history of the war that these documents reveal. From the battle of Midway until the last German code was broken in January 1945, this is an astonishing epic of a war that was won not simply by brute strength but also by reading the enemy's intentions.
The revelations of Stephen Budiansky's dramatic history include how Britain tried to manipulate the American codebreakers and monopolize German Enigma code communications; the first detailed published explanations of how the Japanese codes were broken; and how the American codebreaking machines worked to crack the Japanese, the German, and even the Russian diplomatic codes. The compelling narrative shows the crucial effect codebreaking had on the battlefields by explaining the urgency of stopping the wolf pack U-boat attacks in the North Atlantic, the importance of halting Rommel's tanks in North Africa, and the necessity of ensuring that the Germans believed the Allies' audacious deception and cover plans for D-Day. Unveiled for the first time, the complete story of codebreaking in World War II has now been told.

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Product Details

ISBN-13: 9780743217347
Publisher: Free Press
Publication date: 04/09/2002
Edition description: Reprint
Pages: 448
Sales rank: 442,526
Product dimensions: 5.50(w) x 8.44(h) x 1.10(d)

About the Author

Stephen Budiansky received a master's degree in applied mathematics from Harvard University and worked on classified military studies as a Congressional Fellow. He is a correspondent for The Atlantic, and his articles have also appeared in The Economist, The New York Times, and U.S. News & World Report. He lives in Leesburg, Virginia.

Read an Excerpt



Green water breaking across her flat topside, the U.S. carrier Hornet plunged through a heavy sea and strong wind. A few hours earlier, as dawn broke on April 18, 1942, lookouts aboard the American ship had spotted a Japanese patrol boat. The Hornet's planes were intending to carry out their raid under cover of darkness, but Admiral William Halsey, whose nickname "Bull" had not been bestowed lightly, gave the order to launch at once — wind, wave, and daylight be damned. The ship swung into the wind, and at 7:25 A.M. the first of the twin-engine bombers groaned off the flight deck.

The Army pilots at the controls of the B-25s had practiced short takeoffs from the comfortably dry land of a Florida airstrip but had never once tried it at sea. No one else ever had, either. Landing a B-25 on a carrier was impossible. Flying a B-25 off a carrier was, by comparison, merely insane. But the medium-weight bombers were the only aircraft in the American arsenal with a prayer of completing the daredevil mission. If all went according to plan, they would fly five hundred miles to Japan, drop their load, then continue another eleven hundred miles to a safe landing in unoccupied China.

Leading the attack was an unflappable test pilot, Lieutenant Colonel James H. Doolittle; his was the first of the lumbering bombers to catapult down the heaving deck. Over the next hour fifteen others followed. One pilot hung on the verge of a stall for so long as he struggled to get airborne that, Halsey later recalled, "we nearly catalogued his effects." Thirteen of the planes headed for Tokyo, roared in over the rooftops from different directions, and dropped their four bombs apiece. The three others hit Nagoya and Osaka. Ever since the attack on Pearl Harbor four months earlier, President Franklin D. Roosevelt had been pressing for just such a morale-boosting coup to bolster some of America's wounded pride. The Doolittle raid had been his pet project, and he was exultant with the news. Asked by reporters where the planes had come from, FDR grinned and said, "Shangri-La."

Doolittle's raiders did essentially no damage — except to the Japanese psyche. On that they scored a direct hit. The Japanese Army claimed it shot down nine of the marauders; the true figure was zero. But the premature launch of the planes had added almost two hundred miles to their planned mission, strong head winds burned up still more fuel as they made their way toward China, and most of the crews ditched or bailed out. Eight who landed in Japanese-occupied territory were taken prisoner and three of them were executed, ostensibly for the crime of bombing civilian targets but in reality in an access of Japanese fury and mortification.

In the months since his lightning strike against the American fleet on December 7, 1941, Admiral Isoroku Yamamoto, Commander in Chief of Japan's Combined Fleet, had grown accustomed to the adulation of a grateful public; each day brought sacks of adoring letters. After the bombs fell on Tokyo he was rattled to find he had become the target of hate mail. He was wracked, too, with anxiety over the Emperor's personal safety.

Where had the bombers come from? Yamamoto pointed to Midway Island, America's westernmost outpost in the Pacific since the Philippines, Guam, and Wake Island had been overrun in Japan's seaborne blitzkrieg. It was a plausible conclusion, even if Shangri-La was actually closer to the mark. Midway was twenty-five hundred miles from Japan and thirteen hundred miles from Honolulu. Thus, Yamamoto argued, as long as it remained in American hands, bombers could fly from Hawaii to Midway, and from Midway to strike Dai Nippon. Japan's defensive perimeter would have to be pushed back farther still.

Two days later, Yamamoto's fleet air officer, Captain Yoshitake Miwa, noted in his diary that if further raids on the mainland were to be prevented, "there would be no other way but to make a landing on Hawaii. This makes landing on Midway a prerequisite. This is the very reason why the Combined Fleet urges a Midway operation." But, truth be told, Yamamoto had had his eyes on Midway for months. Untouched by the "victory fever" that swept through Japan's high command, Yamamoto insisted that unless America could be forced swiftly to accept a negotiated settlement, Japan was ultimately doomed. The grand admiral was a gambler and something of a playboy; he had been to Harvard to learn English, served in Washington as a naval attaché, and his knowledge of America's industrial power made him view war with the United States as folly. But if war was inevitable, he had consistently argued, Japan's only hope was to risk all on a knockout blow. America's industrial might would take months or even years to fully mobilize: thus Yamamoto's bold stroke on December 7. Unfortunately, that had left the job only half done. America's battleships had been caught at anchor at Pearl Harbor, but her aircraft carriers, at sea on the morning of the Japanese attack, had escaped.

Throughout March and early April a bitter fight roiled Japan's high command. Yamamoto pressed his case with mounting impatience: To draw the American carriers into the decisive battle, Japan must seize an objective that the United States would have to defend. If his plan to attack Midway was not approved, he would resign. The Naval General Staff sputtered. Midway might be of strategic value to an America on the defensive, the staff insisted, but it was worthless to Japan. Midway was a rocky atoll hardly larger than the small airstrip that stretched from one end of the island to the other; it could hold no more aircraft than a single carrier. The naval staff preferred a thrust to the south to cut off Australia, or, even more ambitiously, to seize Ceylon and India and link up with the German forces in the Near East. The Japanese Army, its eyes on China and on the threat Russia would pose if it entered the Pacific war, declared it would have nothing to do with Yamamoto's scheme, either.

But as the dust from Doolittle's bombs settled, the Army staff came forward with a new demand: It now insisted that the Army must be included in Yamamoto's forthcoming assault on Midway.

Four thousand miles to the east, Midway had become an obsession to another man during that winter and spring of 1942, a man as anonymous as Yamamoto was famous. Commander Joseph J. Rochefort came by his anonymity as much by the nature of his personality as by the necessity of his vocation. Above his desk hung a notice that read: "We can accomplish anything provided no one cares who gets the credit." He would later have reason to question the wisdom of that principle. But putting in twenty-hour shifts in a windowless basement was not a calling that appealed to the glory seekers in the United States Navy anyway. "The Dungeon," they called their cheerless command post in the basement of the administration building at Fourteenth Naval District Headquarters at Pearl Harbor; its more formal name was Station Hypo.

Rochefort had enlisted in the Navy in 1918 with vague dreams of becoming a naval aviator. Nothing but the oddest of chances determined that 1942 would find him in charge of breaking JN-25, the Japanese Fleet General Purpose Code — the code that carried the operational orders of the Combined Fleet, the code that would, in short, tell where Japan was going to strike next.

Rochefort was driven but unflamboyant, a conventional career sailor who had pursued a conventional career path: sea duty, engineering school, ensign's commission, more sea duty. Rising from the enlisted ranks, he was an outsider to the elite fraternity of officers who had graduated from the Naval Academy. The coincidence that deflected him out of the ordinary course of duty occurred while he was serving aboard the battleship Arizona in 1925. The ship's executive officer, Commander Chester C. Jersey, liked crossword puzzles. Rochefort did too. Jersey remembered that fact when he was posted to Navy Department headquarters in Washington later that year. The Navy needed someone to work on codes, and Jersey recommended Rochefort. The informality of it all would seem fantastic by the standards of the huge and bureaucratic postwar Navy. But in 1925, the Navy's cryptanalytic staff consisted of a grand total of one person, and administrative matters throughout the service were frequently settled through personal contact and word of mouth.

Lieutenant Laurance F. Safford, the Navy's one-man code breaking bureau, had not set out to be a cryptanalyst, either. In 1924 he was assigned the task of developing new codes for the Navy. No one in the Navy was paying much attention to foreign countries' codes at the time, and they certainly weren't trying to break them. But Safford figured that to make a good code he ought to first see what other navies were doing. And so the "research desk" was born in Room 1621 of the old Navy Department Building on the Mall in Washington.

When Rochefort showed up for duty in October 1925, Safford put him through a six-month course in cryptanalysis that basically consisted of tossing him cryptograms to try to solve. When Safford was called to sea duty in February 1926, the "course" ended, and Rochefort, more or less by default, found himself officer in charge of the research desk. Under him was one cryptanalyst and one assistant with "no particular abilities." That was it.

Rochefort's first dose of cryptanalysis left him decidedly disinclined for another. It was not that there was any particular pressure on him to produce results. No one in the Navy had much of an idea what he was up to anyway, and no one would have understood it if he had. But the work had a way of generating its own compulsive pressures. Rochefort would come home every evening at five or six o'clock with his stomach in knots from the tension of the problem he was tackling. It would be eight or nine at night before he could manage to force down his supper. He developed an ulcer and greeted his recall to sea duty in 1927 with unfeigned relief.

But in those two years Rochefort scored America's first victory in a long shadow war with the Japanese Navy. Left over from 1918 was most of a $100,000 secret naval intelligence slush fund. To conceal it from Congress, the money was deposited in a Washington bank in a personal account belonging to the Director of Naval Intelligence. Whenever a new DNI took over, his predecessor just handed the money over to him along with the keys to the office. The money had begun to burn a hole in the pockets of successive DNIs, and in the early 1920s the incumbent decided to get rid of some of it by financing a series of break-ins at the Japanese consulate in New York City. The Japanese Navy's "Red" code book was secretly photographed and, over the course of several years, laboriously translated by linguists hired with more of the DNI's secret funds. (Just how hard it was to use up $100,000 was shown in 1931, when an acting DNI, in a fit of conscience for which his successors never forgave him, returned the money to the Treasury. The balance was $65,000.)

A complete code book was a windfall, but there was still one crucial piece missing. Like almost all of the Japanese Navy codes that Rochefort and his colleagues would encounter over the course of their long battle of wits with their Japanese counterparts, Red was an enciphered code. Every word or syllable likely to be used in a message was assigned a numerical value — that was the "code" part. But such a simple one-for-one substitution would not hold up a team of Boy Scouts, much less a determined military foe, for very long. So before the Japanese Navy sent any coded message over the airwaves, it was given a second disguise. The code clerk opened a second book, which contained page after page of random numbers; starting at the top of a page, he added the first of these random "additives" to the first code group of his message, the second to the second, and so on. An indicator buried in the message would tell what page in the additive book he had used for this "encipherment" of the basic code, so that the recipient could turn to that same page and strip off the additive before looking up the meaning of each code group.

Thanks to the DNI's black-bag jobs, Rochefort had the code book. What he did not have was the additive book. To make matters worse, the Japanese changed the additive book frequently. With nothing to go on but the raw traffic that the Japanese Navy put out over the airwaves, Rochefort's job was to reproduce an additive book that he had never seen.

Breaking a code when one has the underlying code book but no additive book is like finding a way across a strange country without a map or a compass. Breaking a code when one has neither code book nor additive book is like finding a way across a strange country with both eyes closed. Doing the former was what had given Rochefort his ulcer in 1926. His task in 1942 was to do the latter.

America's very success, in September 1940, in breaking the Japanese diplomatic cipher, code named "Purple," had the ironic effect of distracting attention from where it could have been more profitably focused in the fateful months leading up to Pearl Harbor. The Purple cipher carried the highest-level diplomatic messages of the Japanese Empire; this was intelligence of such remarkable value that it was given the code name magic. The Purple cipher was generated by a complex machine. It used a cascade of rotating switches to encipher every letter of a message in a different key from the last or the next. In one position of the switches the letter A would become G; in the next it would become P. The U.S. Army's code breakers had, in eighteen months of intense effort, deduced the wiring and setup of the machine without ever seeing one, a feat of pure analysis the likes of which had scarcely before been seen. After hastily soldering together telephone switches and relays to produce a replica of the machine, they proceeded to decode the Japanese messages almost as quickly as they arrived.

On the morning of December 3, 1941, a Purple message came through ordering Japan's embassy in Washington to destroy its code books, and even one of its two vital Purple machines. Frank Rowlett, a senior cryptanalyst of the Army's Signal Intelligence Service, arrived at his office at noon that day from a meeting, plucked this latest magic decrypt from his in-box, and proceeded to read its contents with mounting incredulity. With only a single machine it would obviously be impossible for the embassy to continue its normal flow of business. Colonel Otis Sadtler, who was in charge of distributing the magic decrypts, showed up in Rowlett's office at that moment and began to pepper him with questions. Had the Japanese ever sent anything like this before? Could they be getting ready to change their codes? Perhaps they suspected their current codes had been broken? Then the only possible meaning of this extraordinary message sank in. Sadtler pulled himself to attention. "Rowlett, do you know what this means? It means Japan is about to go to war with the United States!" And, decrypt in hand, Sadtler took off literally running down the corridor of the Munitions Building to alert the head of Army intelligence.

On the night of December 6, an aide interrupted the President at a White House dinner to deliver him the latest magic decrypts. These erased all remaining doubt. Japan was preparing to break off diplomatic relations. War was inevitable.

But diplomatic communications are not the place where military orders are delivered. America knew that Japan was going to strike; it did not know where she would strike. To know that would require breaking into the Japanese naval codes, and there was only one catch: Since mid-1939, America had not read a single message in the main Japanese naval code on the same day it had been sent. For most of the period from June 1, 1939, to December 7, 1941, the Navy was working on naval messages that were months, or even over a year, old.

Partly this was a matter of manpower, partly it was a matter of human nature. Magic was such a dazzling prize that it blinded its possessors to the smaller but sometimes more valuable gems that lay buried among the dross and slag of supply orders and fleet maneuvers. JN-25 was the most recent descendant of the Japanese Navy's Red code; like its predecessors it was an enciphered code. At the time the new code first appeared on June 1, 1939, the U.S. Navy's Washington code breaking staff had grown to about thirty-six hands. By this time the "research desk" had acquired the official bureaucratic designation of OP-20-G, designating it as part of the Office of Naval Communications, OP-20, and Safford was back in charge after several tours of sea duty. The staff of thirty-six included translators, clerks, radio direction-finding experts, intelligence analysts, and officers responsible for the security of the Navy's own codes; only a handful were trained cryptanalysts, and of these only two or three could be spared to work on the new code, which was initially given the designation AN-1.

Over the course of months they laboriously punched every message on IBM cards and searched for any clues that would give them a toehold on this completely uncharted terrain. But everything about it had the air of scholarly inquiry, far from the heat or urgency of battle. AN-1 was a "research" project, not a "current decryption" job; reconstructing the meaning of thirty thousand code groups and piecing together thirty thousand random additives was not going to be the work of a moment. The Japanese Navy's radio signals were intercepted by U.S. Navy operators in Hawaii, Guam, and the Philippines. The operators transcribed the Morse code signals by hand onto message blanks, bundled them up, and once a week handed them over to the captain of one of the Dollar Line's "President" passenger liners that plied the Pacific. The captains, all members of the Naval Reserve and therefore authorized to act as couriers of confidential documents, dropped the packages in the mail to Washington when their ships reached the West Coast. A very small amount of priority traffic could be entrusted to the Pacific "Clippers" of Pan American Airways; in the hull of each of these airplanes a small steel strongbox had been welded into place just for this purpose, the keys held by naval officers along the route. But delays of weeks from the time a message was transmitted by the Japanese to the time it arrived in Washington were the norm.

Throughout 1939, 1940, and 1941 a slow-motion cat and mouse game ensued. Sorting the IBM cards by number and printing out huge catalogues of every code group in every message, the Navy cryptanalysts began to detect a few ghosts of the underlying code. The numbers in each message that appeared to serve as indicators, telling the recipient what page of the additive book had been used, were not quite as perfectly random as they should have been. The numbers bunched up, meaning that some lazy Japanese code clerks were reusing the same pages of additive over and over. That was a classic error; messages enciphered with the same additive pages could in principle be cracked. It was not until fall of 1940, however, that the first real break came — and it came just in time to be rendered obsolete by a completely new, and much more complex, code book that the Japanese brought into service on December 1, 1940.

By the summer of 1941, as tensions in the Pacific grew, every section of OP-20-G was desperately short of help. Messages in the Purple cipher, which could be read in their totality and almost always the same day they were transmitted, claimed first priority. Meanwhile seven thousand AN-1 messages were pouring in each month by mail to Washington, while only sixteen men could be spared to work on them. As the Navy began calling up Naval Reserve officers throughout the summer and fall, that figure crept up by about one per month. Station Cast, the Navy's intercept station at Cavite in the Philippines, was also trying its hand at compiling the reams of printouts and worksheets needed to tease apart the AN code and its additives; since spring 1941 a highly secret collaboration between Cavite and the British government's code breakers in Singapore had been under way on the project as well. But it simply wasn't enough.

Slowly and laboriously, the new code book was being reconstructed; again, inexorably, on August 1, 1941, the Japanese introduced a new, 50,000-group additive book that sent the code breakers back to the beginning. By November 1941 only 3,800 code groups had been identified, along with only 2,500 additives reconstructed in the current system. It was far less than 10 percent of the total, nowhere near enough to read current traffic.

Conspiracy theorists continue to weave elaborate scenarios "proving" that America had advance warning of the Japanese attack, with one branch of the "FDR knew" theorizers insisting that AN traffic was in fact being read in 1941. Yet month-by-month progress reports, internal histories, war diaries, logs — some declassifed only in 1998 — are all in agreement: Not a single AN message had ever been read currently by the time of Pearl Harbor, and not a single AN message transmitted at any time during 1941 was read by December 7.

Five years later, with the war safely won, a few of OP-20-G's cryptanalysts were tidying up loose ends and decided to go back and try to crack the unread AN-1 traffic that had piled up in the months just before Pearl Harbor. What they found was enough to break an intelligence officer's heart. Over and over, the orders to the Japanese fleet during October and November 1941 repeated a single theme: Complete all preparations and be on a total war footing by November 20. Several messages referred to exercises in "ambushing" the "U.S. enemy." And one signal, dispatched November 4, ordered a destroyer to pick up torpedoes that Carrier Divisions 1 and 2 "are to fire against anchored capital ships on the morning in question." None specifically mentioned Pearl Harbor, and indeed many other intelligence indications in those critical months pointed to the Philippines, or even the Panama Canal, as possible targets of Japanese naval action if war broke out. Yet the pre­Pearl Harbor AN traffic, had it been broken at the time, would certainly have conveyed heavy hints of what was to come.

In the chaos following the Japanese attack, mail service from the Pacific was thrown into disarray. On December 4, the Japanese had again changed the additive book for AN-1; it was back to square one yet again, and Washington fretted away a month waiting for enough current intercepts to arrive in the mail to renew the attack. But in the meanwhile the decision was made to allow "the field" to begin work without delay. On December 10, Rochefort's Station Hypo, which had been shunted off to work on a dead-end problem before Pearl Harbor, was given the go-ahead by Safford to tackle AN-1 on its own.

The atmosphere throughout Hawaii in the days following the Japanese attack was one of stunned demoralization. During the attack a spent bullet actually ricocheted off the chest of Admiral Husband E. Kimmel, Commander in Chief of the Pacific Fleet, who would shortly become the scapegoat for the worst military disaster in American history. "Too bad it didn't kill me," Kimmel muttered. Two thousand four hundred and three Americans were dead. Two hundred aircraft were destroyed on the ground: Dutifully heeding warnings to be on the alert, the Army commanders had crowded their planes together wingtip to wingtip in midfield, well away from the perimeter fence and the Japanese saboteurs everyone imagined were lurking about the island. The Japanese torpedo planes and bombers caught all but one of the nine American battleships of the Pacific Fleet in port that morning, and all were left damaged or immobilized by the attack. Arizona, blown in two when her magazine went up, took eleven hundred of her crew with her to oblivion. Oklahoma lay capsized in the mud, never to see action again. The others sank at their moorings, had gaping holes ripped in their sides, or had run aground or were wedged between other crippled ships. Japan's force of ten battleships now had a seemingly insuperable command in the Pacific.

If Pearl Harbor had been asleep, the American forces in the Philippines under General Douglas MacArthur had been comatose. The Philippines had been everyone's bet for where the Japanese blow would fall. When Secretary of the Navy Frank Knox was delivered the news of Pearl Harbor he exclaimed, "My God, this can't be true, this must mean the Philippines!" The Japanese would oblige soon enough. MacArthur received word of the Pearl Harbor attack just as it was ending, at 3:00 A.M. on December 8, Manila time. In the preceding weeks MacArthur had confidently assured Washington that with enough air power he could drive the Japanese back into the sea if they dared to come ashore. On that assurance he had been shipped dozens of top-of-the-line B-17 long-range bombers. When the decisive moment came, MacArthur, apparently frozen in indecision, barricaded himself in his penthouse suite in a downtown Manila hotel and did nothing. Nine hours later Japanese bombers and Zeros appeared over Clark Field; instead of meeting the swarm of enemy fighters they fully expected, the Japanese pilots looked down and rubbed their eyes in disbelief at the sixty neatly parked planes on the field below. That evening, Roosevelt kept a long-scheduled appointment with newsman Edward R. Murrow. FDR pounded his fist on the table in frustration: The American planes had been destroyed "on the ground, by God, on the ground!" he exclaimed.

Three days later, the pride of Britain's Singapore-based Asiatic Fleet, the battleship Prince of Wales and the battle cruiser Repulse, were sunk by Japanese torpedo bombers flying from Saigon. Not a single Allied battleship or cruiser was left west of Hawaii. Japan, for the moment, was the unchallenged master of the Pacific and Indian oceans.

At Pearl Harbor, the thoroughly shaken American commanders were certain that the Japanese were going to hit them again. Crews were hastily set to work tearing down fences, welding them together, and dangling them into the water around the docked ships as crude antitorpedo barriers. "Of course we had no knowledge whether that kind of net would be any good at all," admitted Rear Admiral Claude Bloch, commander of the Fourteenth Naval District, "but it was the best we had." A hypercautious mentality set in, bordering on paralysis. A carrier task force sent to relieve Wake Island was recalled at the last minute by Vice Admiral William S. Pye, who had been given temporary command of the fleet after Kimmel's ouster; the ships were actually in sight of the besieged atoll when the recall order came, setting off a near mutiny aboard the carrier Saratoga. When FDR received the news he said it was a worse blow than Pearl Harbor.

Rochefort, blaming himself for not foreseeing the Pearl Harbor attack, reacted characteristically, driving himself and his men without mercy. Summoned to the Dungeon on December 7 by an 8:00 A.M. telephone call from his deputyLieutenant Commander Thomas Dyer had gone outside to see what all the commotion was and had "caught on fast," he later recalled, when he saw a torpedo bomber three hundred yards away emblazoned with the rising sun insignia — Rochefort rushed to the headquarters he would scarcely leave for the next six months. "I can offer a lot of excuses," he would later say, "but we failed in our job. An intelligence officer has one job, one task, one mission — to tell his commander, his superior, today what the Japanese are going to do tomorrow." He was determined not to be caught flat-footed again.

On December 1 Station Hypo had completed its hasty move from the second floor of the Administration Building to the Dungeon. This was partly for security — the basement was sealed off from the rest of the building, with a single steel door at each end leading directly to the outside — and partly to accommodate a growing staff, which had doubled from twenty-three in June to forty-seven in December. Dyer had managed to get funding to rent a few precious IBM machines back in 1938, but the sensitive equipment had to be kept air-conditioned in tropical Hawaii and that was one detail that apparently got lost in the rush to move to a war footing. When the code breakers took up residence in the Dungeon everyone began hacking and coughing constantly. This went on for two months; finally when Rochefort was able to spare someone for a moment he sent a man to check out the air-conditioning system and see if there was something wrong with it. The man came back shortly and reported he had found the trouble: There was no air-conditioning system. When the air-conditioner finally was installed it tended to function erratically and Rochefort took to belting a smoking jacket over his uniform to ward off the chill when it was running full blast. The smoking jacket became part of the Rochefort legend, as did the pair of carpet slippers he wore to ease his sore feet from standing on a hard concrete floor twenty or twenty-two hours a day. But those who knew him said this painted a false image. He was a tall, thin, pale, and driven man, but he was no eccentric. His quiet doggedness inspired a loyalty that his men never forgot: A half-century later Forrest E. Webb, who ran IBM machines at Station Hypo, would say simply, "Rochefort was my ideal of an ideal man. He never raised his voice, but he knew that what he said was law and everybody believed it. He made sure people knew what they were doing and left them to it." He was a man with a mission.

But they all joked about being crazy. Dyer hung a sign above his desk that read, "You don't have to be crazy to work here — but it helps." He also kept a bucket of pep pills on his desk and every so often reached in, scooped up a handful, and popped them into his mouth. Dyer would often go for forty-eight hours at a stretch. The Dungeon itself was a large open area, about sixty by a hundred feet. The IBM machines were consuming three million punch cards a month and churning out huge stacks of printouts that were kept in boxes or just piled on the floor. There was no time to file or index anything; that led to more jokes about the crazy code breakers. Someone would run across a code group in one message that would ring a vague bell; he would mention it to the others and someone else would immediately reach down halfway into a stack of printouts and pull out a message from a month before.

Hypo was five thousand miles closer to the Japanese fleet than Washington was; it also had its own intercept station for picking up the Japanese radio traffic, just thirty miles away at Heeia. There was no sitting around waiting for the post office to deliver parcels of intercepted traffic, though there was still an absurd lack of the most basic and obvious conveniences of the communications age. No teletype circuit or radio linked Pearl Harbor and Heeia; a jeep, or sometimes a motorcycle or even a bicycle, was dispatched to pick up the intercepts.

The two years of lagging struggle against AN-1, which was now officially known as JN-25, had not been in vain. Although OP-20-G had never managed to catch up with the latest changes in the code book and additive tables, the code breakers by this time thoroughly understood the principles involved. It was just a matter of manpower, and with America mobilizing for war the manpower problem was being addressed swiftly. When Safford had tapped Rochefort for the command of Hypo in June 1941 he promised him first dibs on any officers who had had Japanese language training. After Pearl Harbor, Rochefort took anyone he could get. He cut a deal with the local personnel officer: As new drafts flooded in from the West Coast they would be lined up with their service records and Rochefort would take anyone who looked promising. The personnel office didn't know what to do with the ship's band from the crippled battleship California, left without a job by the Japanese torpedoes; Rochefort said, "I'll take them." The musicians were immediately put to work running the IBM machines. Some would wind up spending the rest of their careers in cryptanalysis.

On March 18, 1942, they caught up at last. The order to begin "current decryption" of JN-25 went out. The war against the Japanese code makers was won. Now the war against the Washington code breakers began.

The odd and ill-defined bureaucratic relationship between Station Hypo and OP-20-G was the stuff that Washington intrigues are made of. Technically Rochefort reported to the commandant of the Fourteenth Naval District in Honolulu, a practical enough man to leave Rochefort to his own devices and let him deal directly with Captain Edwin Layton, the intelligence officer for the Pacific Fleet. But it was OP-20-G that had tapped Rochefort for the job and that loosely coordinated the division of labor among all the various intercept stations. In late January 1942, Commander Safford, Rochefort's old mentor, had been shunted aside in a Byzantine power play at Navy headquarters. Although Washington and Honolulu had established a close collaboration on JN-25, exchanging additive and code groups via a secure radio link that employed the never-to-be-broken SIGABA/Electric Cipher Machine, Rochefort and his new nominal superiors in Washington were on an inescapable collision course. Washington was now demanding central control over all code breaking and intelligence. Safford had been a firm believer in decentralization, and Rochefort insisted he was answerable only to the new Pacific Fleet commander, Admiral Chester W. Nimitz. He was also tactless enough to make it abundantly clear what he thought of Washington's meddling.

The simmering tension broke out into open warfare almost as soon as current reading of JN-25 began. Rochefort had developed a close working relationship with Layton, and the two men would speak by phone several times a day. Layton had come to respect Rochefort's reliability and caution. Both men were fluent in Japanese and Layton knew that Rochefort personally translated more than a hundred of the five hundred to a thousand messages that were being deciphered each day. Knowing that most commanders tended to dismiss intelligence reports as the work of alarmists, and knowing too that Rochefort was never one to exaggerate, Layton routinely upped Rochefort's estimates to compensate for their subsequent discounting. If Rochefort reported four enemy carriers in an area, Layton would change it to six. So when Layton's phone rang on May 14 and he heard Rochefort at the other end of the line exclaiming, "I've got something so hot here it's burning the top of my desk!" he dropped everything and headed right over to the Dungeon. The hot document proved to be a partial decrypt in which the words koryaku butai, invasion force, were followed by the geographical designator AF. Koryaku butai had appeared in orders for the invasions of Rabaul, Java, Sumatra, and Bali that Hypo had already read. AF had been tentatively identified as Midway. Rochefort argued that the clincher was an order that air base equipment was to be shipped to Saipan to be in position for the "AF ground crews." AF was obviously an island air base; it was, Rochefort insisted, a matter of simple deduction to see that it had to be Midway.

Nimitz was quickly convinced. On May 17 he ordered his three remaining aircraft carriers to return at once from the South Pacific. The following day he sent an order to Midway, via secure undersea cable, canceling previous orders to one of the U.S. submarines based there. The new instructions: BELIEVE ENEMY WILL ATTACK MIDWAY USING PLANES LAUNCHED FROM A POSITION FIFTY MILES NORTHWEST OF MIDWAY X PATROL THAT AREA UNTIL FURTHER ORDERS. That same day the Seventh Air Force, at Hawaii, was placed on a special alert; its B-17 bombers were taken off reconnaissance duty and kept loaded with demolition bombs to be ready to carry out strikes against enemy ships on a moment's notice. Other B-17s were moved in from the mainland, and plans were set in motion to fly some to Midway itself.

But then Commander John H. Redman, who had maneuvered himself into the command of OP-20-G in the January reshuffling, began to throw cold water in copious quantities. Washington, in short, rejected Midway as the target of the gathering Japanese offensive. Several weeks earlier Redman had scrawled an irritated note on a memo that had identified AF as Midway: "Comment said AF=Midway, but pointed out that comm. zone designations not identical with area designations." On May 14, OP-20-G had sent an intelligence summary to Admiral Ernest King, the Navy Commander in Chief in Washington, concluding that the Japanese were preparing a "coordinated air and submarine attack on the Hawaiian Islands." Then OP-20-G insisted that Hypo had bungled its additive tables; the Japanese orders were not to attack AF but rather AG, Johnston Island. On May 16 and May 17 OP-20-G was warning of a second Japanese offensive, this one directed against Alaska and the Aleutian Islands. Some intelligence officials in Washington suspected the whole thing was a Japanese deception operation; the real target might even be the West Coast of the United States. A message intercepted May 19 seemed especially fishy. A Japanese seaplane unit informed the Bureau of Personnel in Tokyo that its "next address" would be Midway, presumably so its mail could be forwarded. As Army Chief of Staff George C. Marshall would later note, that seemed to lay it on just "a little bit too thick."

Yamamoto's plan was the most elaborate seaborne ambush ever conceived by the mind of man. Five separate forces, a total of two hundred ships and 250 aircraft including eleven battleships, eight carriers, and twenty-three cruisers, would move across a million square miles of the Pacific in a tightly orchestrated plan. While the Northern Force staged a diversion in the Aleutians, the Striking Force with four carriers and two battleships would neutralize Midway's fighters and bombers, clearing the way for the dozen troopships of the Occupation Force to land five thousand men and seize the island. Meanwhile, a screen of twenty submarines would establish a picket line between Midway and Hawaii to warn when the American carriers sortied from Pearl Harbor to the rescue. That would be the signal for the final act to begin. The Main Body, a huge armada built around seven battleships and a carrier, would hang back hundreds of miles to the west until the American ships committed themselves; it would then spring forward for the kill. Yamamoto would personally command the operation from the battleship Yamato, the world's largest, a seventy-two-thousand-ton vessel whose 18.1-inch guns could throw a thirty-two-hundred-pound shell twenty-five miles. An Estimate of Situation issued just before the battle began by Admiral Chuichi Nagumo, commander of the Striking Force, summarized the Japanese plan, and the Japanese confidence in it: "Although the enemy lacks the will to fight, it is likely that he will counterattack if our occupation operations progress satisfactorily....After attacking Midway by air and destroying the enemy's shore based air strength to facilitate our landing operations, we should still be able to destroy any enemy task force which may choose to counterattack."

Nimitz summoned a final staff meeting for Wednesday, May 27, to review his own estimate of situation. Nimitz was prepared to stake everything on Rochefort's analysis, but it was a huge gamble. It would mean leaving Hawaii defenseless as he rushed his carriers to Midway before the Japanese arrived. Attending the Wednesday morning meeting would be General Delos Emmons, the Army commander in Hawaii, and General Robert C. Richardson, whom Marshall had sent from Washington. In the meanwhile, Rochefort and one of his staff hit on a scheme they hoped would get the meddlers back at OP-20-G to shut up. While attending engineering school at the University of Hawaii, Lieutenant Commander Jasper Holmes had spent some time at the Pan Am repair facility on Midway. He recalled that all of the island's water came from a desalination plant. With Nimitz's approval, Rochefort and Layton on May 19 sent instructions via the undersea cable to Midway. The radio operators there were to send an uncoded "flash" message reporting that the distillation plant was broken. Two days later Tokyo Naval Intelligence sent a signal in JN-25 reporting that "AF Air Unit" had sent a message to Hawaii reporting it had only a two weeks' supply of fresh water and asking for an immediate resupply. The Japanese signal was broken both by Station Hypo and by the U.S. Navy intercept unit in Melbourne, Australia; Rochefort shrewdly laid low and said nothing. The next day Melbourne forwarded the intercept to Washington with the comment, "This will confirm identity AF." To keep the Japanese — and Washington — from learning that it had all been a setup, Layton even arranged for Hawaii to send a reply to Midway reporting that supplies were on the way.

Rochefort stayed up all the Tuesday night before Nimitz's staff meeting going over the months of messages. Disheveled and beat, he showed up half an hour late but was able to avert the wrath of a room full of waiting admirals and generals when he reported that Station Hypo had broken the last remaining piece of JN-25, a separate code-within-the-code used for dates. He then flourished the payoff: a message dated May 26 ordering destroyer escorts for the troopships to depart from Saipan on May 28, proceed at eleven knots, and arrive at Midway June 6. An earlier decrypt had revealed that air attacks against Midway would commence from a point to the northwest of the island on day "N - 12." That fixed the likely day for the Japanese air assault at June 3 or 4.

That same day, May 27, the Japanese changed both the code book and the additive tables for JN-25 and imposed radio silence on the Midway and Aleutian forces. The code breakers were blacked out. But Nimitz had everything he needed already. He knew where the Japanese would strike and with what forces, he knew when, and he knew exactly what he had to do to get there first.

The fast carrier task force had been born of necessity in the aftermath of Pearl Harbor. With the Battle Fleet crippled, Nimitz had studied his assets and reassembled them as best he could into a fighting force. Despite the manifest success of naval air power at Pearl Harbor, and despite the manifest vulnerability of even battleships to air attack, many traditionalists in the navies of America and Great Britain continued to insist that nothing could take the place of the heavily armored and heavily gunned behemoths. Nimitz boldly rejected that view, assigned the few surviving battleships of the Pacific Fleet to convoy duty between Hawaii and the West Coast, and began perfecting the high-speed hit-and-run techniques that carriers made possible. Nimitz's plan for Midway was simplicity itself compared to the baroque evolutions of Yamamoto's plan: He would get there first and ambush the ambushers. To carry out the mission, he had two task forces available, TF 16, with Hornet and Enterprise, and TF 17, which had been composed of Lexington and Yorktown. But the Battle of the Coral Sea had left the Lexington a flaming wreck on May 7. Yorktown was damaged in the same fight by a bomb that plunged through her flight deck and exploded below. Nimitz now ordered the ship to be repaired and ready for action in three days, a job that in peacetime would have taken three months. Fifteen hundred men worked around the clock, shoring up bulkheads with wooden timbers and doing more patching than repairing, but she steamed out of Pearl on May 30, ready for action.

Meanwhile the marines and airmen on Midway itself braced as best they could. The local Marine commander, a First World War veteran who firmly believed in the efficacy of barbed wire, strung miles of it around the island. There was so much dynamite stockpiled that it finally began to pose more of a threat to the defenders than the attackers; tons were dumped at sea in preparation for the Japanese attack. Briefed on the enemy plan, the island's commanders were astonished at the level of detail provided. A facetious rumor went around that Tokyo Rose was on the American payroll and sent coded messages in her propaganda broadcasts.

Nimitz's final orders to his task force commanders instructed them to proceed on the principle of "calculated risk." The war would never be won by commanders who never took a chance. Just don't take foolish chances, Nimitz was saying.

A little before 6:00 A.M. on June 4 a PBY Catalina float plane droned through the bright morning sky. Lieutenant Howard B. Ady and his crew had been searching a sector northwest of Midway since well before dawn. Then came the electrifying message from Ady's plane: PLANE REPORTS TWO CARRIERS, TWO BATTLESHIPS, BEARING 320 DEGREES, DISTANT 180 MILES, COURSE 135 DEGREES, SPEED 25 KNOTS. Only an hour earlier Nimitz had asked Layton to give him a specific prediction of when and where the Japanese carriers would be first spotted. Layton swallowed hard and hazarded 0600, from the northwest at a bearing of 325 degrees, at a distance 175 miles from Midway. When Nimitz received the PBY's report in his operations room he could not resist tweaking his intelligence officer; turning to Layton he dryly commented, "Well, you were only five minutes, five degrees, and five miles out."

Fifteen minutes later a patrol of six Marine F4F Wildcat fighters from Midway ran headlong into a hornet's nest — an incoming wave of Japanese Zeros and bombers. Captain John F. Carey, leading the Wildcats, went after one of the bombers but was instantly struck in the legs by machine-gun fire from the tail gunner. He was able to make it back to Midway and land with both tires punctured, but with no strength in his legs he was unable to apply the brakes. The plane crashed into a revetment and two ground crewmen pulled him from the wreckage and wrestled him to cover — just as the first bombs began to crash about the airfield. Most of the Midway fighter force consisted of slow and outmoded F2A-3 Buffalos, nicknamed "Flying Coffins," and they were no match for the Zeros. Buffalos were so slow that a Zero flying level could outpace a Buffalo in the steepest dive it could safely execute. In all, fifteen of the twenty-six Midway fighters were shot out of the sky; others landed in the midst of the Japanese bombing and were destroyed on the ground. Only two of the planes would ever fly again.

But Midway was better prepared with antiaircraft armament, and that evened the score. Sixty-seven of the 108 Japanese attackers were destroyed or damaged so badly as to be put out of action. At 7:00 A.M. Lieutenant Joichi Tomonaga, leading the attack, urgently radioed Nagumo: another strike was needed. Nagumo agreed, then hesitated. Ninety-three aircraft aboard the carriers Akagi and Kaga had been held back from the first wave, fitted with torpedoes and armor-piercing bombs to be used against any American ships that might appear. But there were no reports of American ships; surely the U.S. carriers were still back at Hawaii. Nagumo hesitated a few more minutes, then finally gave the order to replace the planes' weapons with land-attack bombs. The process would take an hour.

Reconnaissance was not a strong point of the Japanese Navy. At 7:28 A.M. a float plane reported ten enemy ships; it took the plane another forty minutes to incorrectly identify them as cruisers and destroyers, and it was almost a full hour after his initial report that the pilot almost casually added: ENEMY FORCE ACCOMPANIED BY WHAT APPEARS TO BE AN AIRCRAFT CARRIER. Alarmed, Nagumo ordered the armament changed out once again in preparation for a strike against the American carrier. But at that moment Tomonaga's returning strike force was circling and running dangerously low on fuel, waiting to land. They would have to be recovered first, refueled, and relaunched before the bombers could be brought up to the flight decks — still more maddening delay.

In command of TF 16 was Admiral Raymond Spruance, who had taken Halsey's place at the last minute when Halsey had been packed off to a Honolulu hospital suffering from an odd dermatitis that covered his entire body. Spruance was almost the opposite of the pugnacious Halsey, a cerebral and even cautious commander with cool, steady judgment. But in the Battle of Midway, Spruance stretched "calculated risk" to the limit. When the Japanese Striking Force was located, Spruance quickly determined that it would be several hours before he would be in the best position to launch his planes. He decided not to wait; risking everything, he let loose with an all-out attack at once. Spruance knew that striking immediately would increase the odds of catching the Japanese ships at their point of maximum vulnerability, just as they were recovering the Midway strike force. He also knew it meant that his own torpedo bombers would run out of fuel before they could make it back to their ships. With luck they might be able to land at Midway; more likely, they would have to ditch their planes and make the best of it.

The Japanese had already dodged a series of ineffectual attacks from Midway-based B-17 and B-28 bombers and outmoded SBU Vindicator dive bombers (the pilots of the latter sardonically called them "Wind Indicators" for their habit of spinning around when landing in a crosswind). The American carriers were equipped with more modern aircraft, but these at first seemed destined to the same fate as the Midway force. Three squadrons of TBD Devastator torpedo bombers were cut to pieces by antiaircraft fire and by the swarm of fifty Zeros protecting the Japanese fleet. It was almost a massacre: Of the forty-one planes that attacked, only four made it back. But just as the melee was ending at about 10:20 A.M., forty-nine SBD Dauntless bombers from Yorktown and Enterprise slipped in unnoticed at fourteen thousand feet. Lieutenant Commander Clarence Wade McClusky, air group commander of the Enterprise, had led thirty-two of the Dauntlesses to the Japanese fleet's last reported position only to find empty ocean. Running short of fuel, he at last spotted the wake of a Japanese destroyer and decided to follow it. The decision paid off: A few minutes later, and there below him, in full view, were Kaga and Akagi. McClusky pushed his nose down, heading straight for the carriers in a seventy-degree dive. Kaga, its deck crowded with planes and scattered with armament and fuel lines, took a direct hit. The ship's communications officer hurried toward the bridge to urge the captain to move to safety; then two more bombs struck, and when he looked again the bridge was gone. Akagi's deck went up in a chain reaction of exploding planes and armament. Commander Minoru Genda, air officer of the First Air Fleet, who had been confined to bed with pneumonia and who had dragged himself, feverish, to the bridge to watch his air crews launch the first wave, now surveyed the carnage and uttered a single word of ironic understatement: Shimatta — "we goofed." The carrier Soryu meanwhile was hit twice by the Dauntless squadron from Yorktown, led by Lieutenant Commander Maxwell F. Leslie. The ship erupted in flames so intense that the hangar doors melted. The fourth Japanese carrier, Hiryu, shrouded in haze, escaped for the moment, and she at least would have her revenge. Hiryu immediately launched an attack against the Yorktown; one bomb smashed through the ship's side and sailed through the coffee urn in the ready room before lodging in the stack and exploding, knocking out five of the boilers and slowing the ship from thirty knots to a crawl. A series of torpedo hits finished her off, and the order to abandon ship was given at 2:55 P.M.

But the American forces would have the final word that fateful day. All airworthy dive bombers left on the Enterprise, twenty-four planes, were ordered out against Hiryu. No fighter escort could be spared; they had to remain to protect the American ships. At 4:45 P.M. the dive bombers spotted the enemy, and four bombs set her ablaze. In the space of a day, four of the six carriers that had launched the attack against Pearl Harbor had been destroyed. Japan lost more than three hundred aircraft and three thousand men. Yamamoto had obtained his decisive confrontation.

Nagumo kept the news from Yamamoto as long as he dared; when the Commander in Chief was finally told that his gamble had failed, he sank into a chair stunned and speechless. Demoralized and hesitant, Yamamoto at first ordered a cruiser bombardment of Midway for the following morning, then countermanded it. Yamamoto's huge battleship force, stripped of its air cover, was now like a short-armed, muscle-bound boxer. It could only land a blow against an opponent who grappled in a close embrace, and Spruance prudently kept his distance, pulling back to the east through the night to where he could still threaten with his aircraft without being threatened by Japanese guns. Yamamoto's huge battle force still outgunned the Americans by orders of magnitude. But with his carriers gone, he was left with no choice but to retire from the battlefield.

The most direct result of the Battle of Midway was to halt the tide of Japanese expansion. From the moment Yamamoto's ships steamed to the west in confusion and defeat, Japan was on the defensive, and would remain so throughout three grueling years of island combat. In the three months following Pearl Harbor, Japan had been an unstoppable juggernaut, seizing oil and rubber fields that her war machine so vitally needed in South Asia, throwing out a thousand-mile-deep defensive perimeter in half the time war planners had allotted for the task. Now, in a day, the Imperial Japanese Navy had suffered its first decisive defeat in three centuries, and Japan was in the entirely new position of trying to cling to what she had conquered, rather than looking to new conquests.

But Midway was also one of those moments that concentrate forces of history, that in one intense burst crystallize what might have otherwise taken years to coalesce from the fog of events. Midway decisively announced the end of the age of the battleship: The battleship's brawn was simply no match for the long reach of the carrier. Of even farther-reaching consequence, the American victory at Midway moved code breaking and signals intelligence from an arcane, little-understood, and usually unappreciated specialty to the very center of military operations. Even Nimitz, a rare example of a true intellectual among military commanders, had been doubtful about the value of "radio intelligence," as it was then known; if it had failed at Pearl Harbor, he reasoned, it did not make sense to place much faith in it. Layton had persuaded him otherwise, pointing out that JN-25 had not been cracked in time to warn of Pearl Harbor and that the Japanese Navy had maintained radio silence during the actual operation. But most commanders looked upon intelligence in general with suspicion, if not with the outright contempt that was the characteristic view that men of action of that era held for subtlety or innovation. There was certainly nothing subtle about the huge billboard that Halsey ordered erected on a hillside on one of the Solomon Islands. Visible to passing ships it bore a simple and crude admonition to his troops:

You will help to kill the yellow bastards
if you do your job well.

The way to win, in the view of such fighting admirals, was to fight — and think about it later, if at all. The Battle of Midway was won through fighting, to be sure. Bravery, resourcefulness, and a not inconsiderable dose of luck all played their part. But the one indispensable element in the victory was the thinking, and nothing but thinking, that had cracked JN-25.

Three days after the battle ended, Rochefort told everyone at Station Hypo that he "didn't want to see them for three or four days." He expected everyone would just go home and catch some sleep. Instead the code breakers organized a house party on Diamond Head and got their boss up there; it wound up, Rochefort later recalled, as a "straight out-and-out drunken brawl" that lasted the entire three days. Rochefort said he was grateful for one thing: The party's organizers at least had had the sense to stay away from a hotel, which might have left them to the tender mercies of the shore patrol. Then everyone shook off their hangovers and went right back to twenty- and twenty-two-hour shifts to tackle the new code book and additives that the enemy had just introduced into JN-25.

The denouement of the Battle of Midway was not one of the U.S. Navy's finest hours. An outnumbered, outgunned, and battle-stricken force had just changed the course of history through a feat of code breaking and intelligence analysis that laid bare the enemies' intentions; scarcely ever had a military commander known so precisely what the opposing commander was planning and thinking. Nimitz was full of praise for Rochefort and his men. Nimitz enthusiastically forwarded to Admiral King in Washington a recommendation from the Fourteenth Naval District commandant that Rochefort be awarded the Distinguished Service Medal for his part in the victory. Rochefort, with a keener measure of Washington politics than his commander, strongly advised against it: It would only "make trouble." He was right. Redman was continuing his campaign to centralize control of all radio intelligence work under OP-20-G in Washington and Rochefort was continuing to resist; it was quickly degenerating into a fight over who deserved credit for breaking JN-25 and correctly anticipating the Japanese plans for Midway. The honors for breaking JN-25 were properly shared. Of the 110 vital messages broken in advance of Midway, 49 were read simultaneously by both stations, 26 by Hypo only, and 35 by Washington only. But when it came to drawing the correct conclusions from those messages, Hypo won hands down. Had Nimitz been swayed by Washington's analysis, the Japanese ambush would very likely have succeeded.

Yet Redman was now claiming sole credit for the victory at Midway, and in that atmosphere there was no way he could let an award for Rochefort go through without a fight. Just a few weeks after Midway, on June 20, Redman sent a memorandum to the Vice Chief of Naval Operations baldly asserting that "experience has indicated that units in combat areas cannot be relied upon to accomplish more than the business of merely reading enemy messages and performing routine work necessary to keep abreast of minor changes in the cryptographic systems involved." Simultaneously, Redman's older brother, Captain Joseph R. Redman, now Director of Naval Communications, was complaining that Station Hypo was, "by virtue of seniority, in the hands of an ex-Japanese language student" who was "not technically trained in Naval Communications." Rochefort should be replaced with "a senior officer trained in radio intelligence rather than one whose background is in Japanese language," he insisted. The Redman brothers' behind-the-scenes lobbying paid off two days later when Admiral King accepted the advice of his chief of staff and denied Rochefort a medal. The argument, as officially stated, was that Rochefort had "merely efficiently used the tools previously prepared for his use," which had a grain of truth, and that "equal credit is due" to Washington for "correct evaluation of enemy intentions," which was a whopper. King the next day sent "all U.S. Naval radio intelligence activities" a "well done," the naval equivalent of a pat on the head.

A year later, Commander John S. Holtwick, who had run the IBM machines at Station Hypo, called on Joseph Redman, now a rear admiral. In the course of conversation Redman casually remarked that Station Hypo had "missed the boat at the Battle of Midway," but Washington had saved the day. The lie took Holtwick's breath away — especially since Redman had to know that Holtwick knew the opposite was true. That was the first real inkling the Hypo crew had of how completely Washington had stolen credit for the victory at Midway. Shortly before his death in 1985, Dyer wrote: "I have given a great deal of thought to the Rochefort affair, and I have been unwillingly forced to the conclusion that Rochefort committed one unforgivable sin. To certain individuals of small mind and overweening ambition, there is no greater insult than to be proved wrong." Two of the Station Hypo team, Dyer and Holmes, finally did receive the Distinguished Service Medal after the war. Rochefort finally did, too — in 1985, nine years after his death.

The Redmans' argument in favor of centralization was not entirely phony. The loose organization of the Navy's intercept units made less sense in a day of secure radio links and rapid exchange of information than it had even a few years before. There was also a pressing need to avoid unnecessary duplication in the huge labor involved in breaking a new code, as well as a need to make sure that all relevant intelligence bearing on a given problem came to a central point for correlation. But centralization became a convenient club to beat Rochefort with, and the Redman brothers beat away unmercifully. Finally on September 15, Rochefort, with Nimitz's approval, sent a blistering memo insisting that he in effect was answerable only to Nimitz, and Washington should butt out . Payback came on October 22, 1942: Rochefort was summoned to the Navy Department for "temporary additional duty." When Nimitz protested, he was assured that Washington simply needed Rochefort's expert advice. Rochefort once again read the situation more accurately than his boss; he told everyone that he was not going to be coming back. A month later Nimitz received a letter, which had traveled via surface mail, informing him that Rochefort's "temporary" duty had become "permanent." Nimitz was furious, and for two weeks refused to speak to John Redman — who, in an odd turn of events, had since been promoted to become Nimitz's fleet communications officer. But in the end there was nothing Nimitz could do about it.

Rochefort, meanwhile, proceeded to make "several mistakes in a great big hurry," as he himself put it. Worn out, suffering from bronchitis, and made more prickly than ever by the Redmans' attempt to steal the credit for his work, Rochefort said he would not accept any assignment in radio intelligence unless he was sent back to Honolulu as officer in charge. Failing that, he demanded combat duty. Cryptanalysts were forbidden to enter combat zones: they knew too much that they might give away if captured and tortured by the enemy. But Rochefort pulled every string he could think of and was offered command of a destroyer, only to turn it down because the ship was leaving at once from San Francisco and he had promised his wife they would visit their son at West Point that same weekend — "a very stupid thing for me to have done," Rochefort later said. He ended up in command of a floating dry dock in San Francisco. He never worked on codes again.

Copyright © 2000 by Stephen Budiansky

Table of Contents


List of Maps

Prologue: Midway

1. "No Good, Not Even for Intelligence"

The end of the Black Chamber / William F. Friedman picks up the pieces / "I had the good sense to get out of it!" / Room 40 / Winston Churchill, an early convert / The Foreign Office, a late convert / The Soviet intercepts / A strategic failure for intelligence

2. Nature of the Beast

The birth of codebreaking / Machine ciphers, Poland, and the Enigma / Depth reading / The distinct limitations of thievery / Solving the Red machine

3. "Il y a du Nouveau"

1939, a dark new year / Meeting at Pyry Forest / Marian Rejewski's mathematical feat / Recovering the daily Enigma keys / Alan Turing and other "men of the professor type" / Bletchley Park / The Poles' flight

4. Fighting Back

British mathematicians vs. the Enigma / The bombe takes shape / "A pile of dull, disjointed, and enigmatic scraps" / Cryptanalytic talent / Norway and Yellow / France and Red / HMS Glorious

5. Impossible Problems

The sinking of U-33 / Naval Enigma and the bombe / Operation ruthless and other straws / American isolationism / Purple / The British charm offensive / A mission to Bletchley, bearing gifts

6. Success Breeds Success

The Blitz / Cape Matapan / Boniface, barbarossa, and Bismarck / Naval Enigma, U-110, and the trawler pinches / The eastern front and German atrocities / Trafalgar Day / Cribs and continuity

7. The Machines

The British make polite noises / IBM machines and JN-25 / The machine attack on Floradora / Washington at war / Military vs. civilians / An American ultimatum / Better bombes / High-speed analyzers

8. Paranoia Is Our Profession

Dönitz's suspicions / The evacuation of Corregidor / The Midway leak / Some bungled operations / "do not talk at meals" / Suspicions among friends

9. The Shadow War

Calling the shots in the Mediterranean / torch and deception / The flight from Vichy / Atlantic convoys / U-559 and the breaking of Shark / The hunt for leaks / The American invasion / Pressures and diversions / Women in uniform

10. Command of the Ether

Russian espionage and Project venona / GEE and Fish / Masters of deception / Yamamoto / The Water Transport code / Failure in the Ardennes / Signaling the end

Epilogue: Legacy


A. Chronology

B. Naval Enigma: Its Indicating System and the Method of "Banburismus"

C. Cryptanalysis of the Purple Machine

D. The Intercept Network

E. Rapid Analytical Machinery (RAM)


Glossary and Abbreviations




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