War of Shadows

by Gershom Gorenberg

  One night in January, John Herivel heard a knock on his door in Cambridge. He opened it; Welchman slipped in. Welchman had supervised the young mathematician from Belfast for two years, then vanished at the beginning of the third. Herivel was fit for army service but had permission to finish his honors exams that year before being called up. Welchman asked his student to join him in “very important war work” at Bletchley Park instead.

  Herivel said yes. The university had become “a ghostly place,” with everyone leaving. He was on the train a few days later, though Welchman hadn’t actually explained what the work was.

  Job offers for the Government Code and Cypher School were always cryptic. Only when you got to Bletchley Park and signed the Official Secrets Act, to acknowledge you were bound by it, could you be initiated into the esoteric knowledge of your job—and of no other job. Another twist was that once in, you couldn’t get out. “A girl who had broken her heart and wanted to get away to give it a chance to mend” could apply for a transfer, one staffer wrote. She “might find sympathy but would not get release.” A man couldn’t decide he wanted to go fight in the war, even if he was embarrassed to have a desk job he couldn’t describe while other men were dying, even if his old headmaster wrote to him and told him he was a disgrace to his school, as happened. No one would let him take the chance of being captured.10

  There’s no trace of how Margaret Storey got to Bletchley Park in the early part of 1940. The trace she left in life was the work she did there, which she never wrote about or spoke about. People who knew her assumed she had a university education. If so, it was not from Cambridge or Oxford, the usual recruiting grounds for GC&CS. She and her sister Penelope may have been recommended by one of the people of the right class, those who assumed that their class was best suited to keep secrets. They may simply have applied for work at the Foreign Office when the war began. She was born in Ceylon, where her father owned a tea plantation. As befits a colonial gentleman, he wrote a book called Hunting and Shooting in Ceylon. Her colonial childhood may explain her ability to absorb languages; she eventually spoke at least nine fluently. Someone who worked with her mentioned Turkish, another said Russian.

  In any case, Margaret Storey started at Bletchley Park at the rank of untrained clerk. She was a slight woman, twenty-two years old and extremely shy, who dressed in browns, spoke the precise English of a BBC announcer, remembered every word she heard and read, and identified flowers and birds by their Latin names. She had a sense of humor, but she treated it as if it were covered by the Official Secrets Act. To her good fortune, a cloister of peculiar geniuses was a place where a woman like that could be noticed.11

  GALEAZZO CIANO, MUSSOLINI’S son-in-law and foreign minister, appointed the son of Field Marshal Badoglio, the chief of the general staff, to an ambassadorship. “He is no ace, but his father adores him, and I intend to keep his good will at all costs. He is a valuable ally in the cause of non-intervention,” Ciano logged in his diary at the start of the year.

  Badoglio’s erstwhile partner in the riconquista of Libya, Field Marshal Rodolfo Graziani, the Butcher, was now the army chief of staff. He “favors war at the side of Germany and tries to persuade the Duce to hasten it,” Ciano wrote in his precise handwriting. Graziani had “more ambition than brains,” Ciano fumed. Pietro Badoglio, on the other hand, understood that Italy was short on raw materials, that rearming “would take all of 1941, and not even in 1942 will we be able to take offensive action.” If Ciano had any scruples, which is a matter of debate, they were not about invading and conquering countries. He opposed only trying to do it without an army fit for the job.

  He thought of nothing but convincing the Duce to stay out of war. The usual gossip went missing from his diary entries. At times he thought he was winning. Mussolini “at last has become well acquainted with the state of the army,” his son-in-law wrote in mid-January. “The number of divisions that are ready are ten; by the end of January there will be eleven. The others lack everything more or less. Some are 92 percent lacking in artillery. Under these conditions it is crazy to speak of war.

  “Mussolini… is discouraged to the point of feeling the symptoms of a new stomach ulcer.”

  In those words, one could also hear what Mussolini ached to do. The Duce let out his frustration at the Germans. Ciano wrote of a conversation with his father-in-law: “He says, ‘They should themselves be guided by me if they do not want to make numerous unpardonable faux pas. In politics it is undeniable that I am more intelligent than Hitler.’” In his diary entry, Ciano added what he had kept to himself: “I must say that until now the Chancellor of the Third Reich doesn’t appear to share this opinion.”

  Italy was desperately short of both foreign currency and coal. Britain offered a trade deal that would include coal. “The terms are not bad,” Ciano wrote in early February. A memorandum from the British ambassador said that an absolute condition for the deal was that Italy sell arms and ammunition to Britain. Britain’s gambit was that an agreement would speed its own preparations, while keeping Italy out of war. Ciano was in favor. The Duce vetoed the deal. Italy needed the arms, he said. Besides, he’d made promises to Germany, and “morality and honor” required keeping them. Ciano passed this on to British ambassador Percy Loraine in mid-February. Loraine replied—in Ciano’s paraphrasing—that “relations between our countries are really moving to a period of greater difficulties.”

  (If Loraine sent that assessment to the Foreign Office in London, and if it ricocheted from there to the War Office and onward to headquarters in Cairo, it did not lead General Wilson to reread Bagnold’s proposal.)

  Germany did supply coal to Italy but could not transport enough by land. It had to come by sea in Italian ships. At a social affair, Loraine told Ciano that as of March 1, Britain would enforce its blockade of German trade and interdict the ships.

  Sumner Welles, the US undersecretary of state and President Roosevelt’s personal emissary, came to Rome to convince Italy to remain neutral. Ciano found him “distinguished in appearance and in manners,” a gentleman, in contrast to “the pack of vulgarians that make up the German leadership.” Mussolini met Welles. Afterward he told his son-in-law, “Between us and the Americans any kind of understanding is impossible because they assess problems on the surface and we go deeply into them.”

  The day before the British blockade on coal began, Ciano wrote of hearing that Mussolini had said, “There are still some criminals and imbeciles in Italy who believe Germany will be beaten. I tell you Germany will win!”

  Ciano commented, “I accept ‘imbecile’ if it is for me, but I think ‘criminal’ is unjust!”12

  JOHN HERIVEL WAS billeted in a house down the road from Bletchley Park. The landlady gave him a sitting room where she served him dinner. This was awkward, because he knew well that “landlady” meant “the lady of the house who had been required by an all-powerful war-time government to give me board and lodging in her house.” After she cleared the dishes and shut the door each evening, he settled into a plush armchair that may have dated to Queen Victoria’s reign, smoked his pipe, and listened to the hiss of the coal fire in the fireplace and the crunch now and then of someone slogging through the snow outside. All day he’d been thinking Enigma. If you’ve been arranging and rearranging pieces of a puzzle for many hours without getting them to fit, and then you relax in front of the fire, all you can think of are puzzle pieces.

  One night in late February he dozed off. He woke with a dream fleeing his mind. “I was left with a distinct picture… of a German Enigma operator.” He had double good fortune: For one thing, the picture ignited ideas. For another, his pipe had not set fire to the rug while he dozed.13

  Two months earlier, at the end of 1939, Dilly Knox had mixed a strong punch and held a party in the cottage: Alastair Denniston, as the director, ceremonially cut the last of two million holes in the cardboard sheets, completing one set for Bletchley Park and one set for the Poles.14 The cottage team searc
hed intercepted messages and found repeats in the first six letters of messages. They arranged the sheets—and came up with nothing. No Enigma breaks.

  The best suggestion of what to do next was to ask Rejewski, Rozycki, and Zygalski for technical help. The three mathematicians, along with other members of the Polish Cipher Office who’d succeeded in reaching France, were now at what was called Command Post Bruno, in a chateau at Gretz-Armainvilliers, twenty-five miles outside Paris. There they worked with French military intelligence under Gustave Bertrand. Denniston wrote to Stewart Menzies, who was now “C” because Sinclair had died. Menzies wrote to the head of French intelligence and asked that Bertrand send the Polish trio to England.15

  Bertrand said no. He explained that the French government was now paying the salaries of the remnants of the Polish army who’d regrouped in France, and “therefore the Poles must work in France.”16 Bertrand apparently feared that once in England, they wouldn’t come back, and he would lose his assets.17 Britain’s chance to get Rejewski and friends had evaporated the autumn before in Bucharest when an anonymous British diplomat said he’d have to wait for instructions before helping them.

  Dilly Knox offered to go to Paris. Denniston turned him down, perhaps recalling the “deplorable experiences” with him in Warsaw. Turing went instead, alone, in mid-January. Evidently, Denniston considered him quite capable of navigating people’s feelings. By some accounts, it turned out that the Poles had sent mistaken information about the recently added fourth and fifth Enigma wheels.18 When that was straightened out, the sheets worked. It’s equally possible, though, that the British simply needed better instructions in how to use them.

  Either way, the Poles and Turing managed to solve an Enigma key, probably for January 17. For the first time since the war broke out, they read new messages. A few days later, Turing was back, and Dilly’s team was breaking keys in the cottage.19

  Dilly sped up the process by noticing two habits of German operators. When they chose their indicator and a wheel setting at the start of a message, they were supposed to pick three random letters for each. But people aren’t random creatures. They like letters that join up, that mean something. So German operators would use sets like “HIT-LER” or “BER-LIN” or girls’ names, such as “MAR-THA” or “CIL-LIE.” The last of those apparently gave rise to the Bletchley Park term “cillies” for such telltale patterns.

  Then, when sending a message in several parts, they sometimes looked at whatever letters were showing at the top of the wheels at the end of one part, and sent that, unencrypted, as the indicator for the next one. Looking out for those mistakes, you could cut down on the number of possible settings, and using the sheets became much quicker. Milner-Barry, the classicist whom Welchman rescued from stockbroking, kept a catalogue of German security breaches. Instead of studying the tragic flaws of Sophocles’s characters, he became expert in the fatal errors of anonymous Nazi code clerks.20

  By the time Herivel got to Bletchley Park on January 29, Welchman’s crew had moved into Hut 6. Next to it, in Hut 3, a new team—an officer each from the air force, navy, and army and a Foreign Office man—had the job of translating the messages to reveal the treasure of useful intelligence.

  When they read the deciphered messages, they found that the treasure was usually still hidden.

  Blue was a practice key, used for training operators. The text was often nursery rhymes. Red was a richer vein: the key of the Luftwaffe, the German air force. But the German words “still bristled with obscurities.” The Germans wrote in their own abbreviations and military jargon. They used codenames. They used numbers that stood for bases, targets, airfields, trains, and coordinates on German maps. They sent lists, in which only the quantities appeared because sender and receiver knew what item came first and second and tenth. So the number 423 in a list could mean that many airplanes or troops or tons of fuel.

  “We were eavesdroppers,” a Hut 3 man wrote, “strangers reading stolen scraps of other people’s correspondence.”

  Knowing German wasn’t enough. They needed to learn a new language, with no one to teach it. They needed to keep track of words and names and find connections. The translators had to become codebreakers themselves.21

  Besides that, with the sheets and Dilly’s cillies combined, Hut 6 was having only “occasional successes” at finding the daily settings.22 In late February, in his armchair in front of the fire, Herivel was looking for a new way in.

  He was a mathematician. His dream, though, told him to think not about numbers but about a person—about the clerk with the machine, a soldier, still awake at midnight or half awake before dawn, when he had to rotate the letter rings on his three Enigma wheels. The new day’s settings specified which letter on each ring had to line up with the starting mark on the wheel. After setting the ring, the soldier had to put the wheels into the machine. Because of how the Enigma was built, the easiest way to insert the wheels was with the three letters from the daily ring settings on top.

  Five minutes after midnight, or maybe at dawn, an officer would hand him the day’s first message to encipher. Before sending a message, he was supposed to move the wheels so that three other letters, chosen randomly, would show. Those would be the indicator, which he would send openly, unencrypted.

  But if he was tired, or under pressure, or both, it would be so easy not to move the wheels. In that case, his indicator would be the same as his ring settings—the ring settings for everyone using that key. If it were Red, for instance, he would openly send the ring settings for the entire German air force. Or maybe, being both lazy and careful, he’d move each wheel by a letter.

  If a couple dozen or thirty or fifty operators did that, Herivel thought, someone looking at a stack of intercepted German messages would see an unnatural concentration of very similar indicators. The ring settings might just be inside that cluster. You might be able to test just those couple dozen variations and find the settings for that day.

  The flaw in the machine was the man. The flaw in the machine’s design was forgetting that people—tired people, stressed people, people who don’t think randomly—would use it.

  Herivel told Welchman his idea. Welchman lit up, and told him to start charting indicators. It was the beginning of March. Herivel started looking for clusters.

  The idea didn’t work. He was unable to find clusters of very similar indicators that revealed the daily key.

  In the meantime, the British Tabulating Company delivered the first of Turing’s bombes in mid-March. It did work, with the spinning wheels testing one hypothetical wheel setting and then another to see if any of them could have turned a likely snippet of German text into what appeared in a message. But testing one setting at a time turned out to be much too slow to be useful.

  Welchman sat down one day with his colored pencils. An idea had flashed in his mind for a way to rewire the bombe so that it checked twenty-six hypotheses at a time. He rushed to Turing to show him his drawing.

  He got a much warmer response than he had from Dilly with his previous brainstorm. “Turing was incredulous… as I had been, but when he studied the diagram he agreed the idea would work, and became as excited about it as I was. He agreed that the improvement… was spectacular.” Or rather, that it would be, once the factory could build a new bombe. They had months to wait.23

  Herivel, for his part, kept making his charts every day. He wouldn’t be able to explain why, except to say that “I may simply have felt in my bones that such a beautiful theory… must be right.” When he had an evening shift, someone on an earlier shift would fill in the chart for him. The thing to do, if you’d tried an idea and it hadn’t worked, was to keep trying till it did.24

  6

  THE ORACLES

  Spring 1940. Bletchley Park–France–Rome.

  ON APRIL 7, Harry Hinsley turned a crank on an old-fashioned telephone that connected him to the Operational Intelligence Center at the British Admiralty. Hinsley’s job at Bletchley Park was tra
cking the wireless traffic of the German navy. He read the call letters of intercepted messages, and their frequencies, and information on the direction from which the radio signals had come. The autumn before, as he was about to start his third year studying history at Cambridge, two of his instructors put his name down on a very short list of top students for GC&CS. John Tiltman and Alastair Denniston, the gale and the whisper, came to the university, interviewed him, and offered him a job without telling him what it was. Now he puzzled out the locations of ships and land stations, and who talked to whom. He became the “leading expert outside Germany on the wireless organization of the German Navy,” for the simple reason that no one else knew anything. He couldn’t read the messages, but knowing who was talking, and from where, was the next best thing.

  On this particular day, he phoned to say that German ships were talking by wireless in North Sea waters west of Denmark and in the narrow passage that led out of the Baltic Sea. This was something completely new, Hinsley said; he hadn’t seen traffic from there before. Afterward, he’d figure that the intelligence officers at the other end of the line hadn’t paid attention because he was a young civilian and because what he was doing, a craft called traffic analysis, was new to them.1

  Alan Turing’s team had yet to break into German naval Enigma. But the Naval Section at Bletchley Park had solved some more conventional codes and ciphers. One was used by merchant marine ships that had been put under the command of the German admiralty. In early April, a codebreaker named Christopher Morris deciphered a message telling ships sailing toward the Norwegian port of Bergen to report their positions to the army high command in Berlin. He was told he’d made a mistake; ships wouldn’t report to the army; he should decrypt it again. He did; it still said the same thing. The translation wasn’t passed on.