Seizing the Enigma (16 page)

Once again, as in World War I, Britain had obtained the means for solving her adversary’s messages through a gift from a loyal ally.

E
ARLY IN
1919,
PROFITING FROM THE LESSONS OF THE
G
REAT
W
AR
, the British cabinet had decided to establish a permanent codebreaking agency. The first lord of the Admiralty, who was both interested in intelligence and politically powerful, captured the agency for the navy, perhaps in part because it ran most of the intercept stations that provided the cryptanalysts with raw material. The director of naval intelligence, Captain Hugh (Quex) Sinclair, began by recruiting veterans of the navy’s Room 40 and the army’s M.I.1b. In particular, he brought in the two brightest lights of those bodies, Room 40’s Dillwyn Knox, and M.I.1b’s Oliver Strachey (the older brother of the Lytton Strachey who, years before, had tried to seduce Knox). Sinclair put Alastair Denniston in charge. Denniston, known because of his stature as “the little man” to his subordinates, was not the best administrator: one person spoke of him viciously “as possibly fit to manage a small sweet shop in the East End.” But Denniston’s dislike of hierarchy protected his individualistic cryptanalysts from the rigidities of bureaucracy. And his knowledge of the subject matter, his informality, and his willingness to delegate responsibility helped him build and sustain a secret government department of great value.

The new organization, which had the public function of securing the government’s communications and the secret one of reading foreign governments’ messages, was given the deliberately misleading name, proposed by a Foreign Office staffer, of Government Code &
Cypher School. It officially came into being November 1, 1919, with 66 staffers—29 professional and 37 clerical, 12 of these for constructing British codes. A year and a half later the new foreign secretary, Earl Curzon of Kedleston, who had long wanted control of codebreaking, took advantage of a political leak of some Soviet solutions and of the fact that the first lord of the Admiralty had been replaced by a man who had neither his political clout nor his understanding of intelligence and who was glad to reduce costs. By April 1921, G.C.&C.S. was under the practical control of the Foreign Office, and by April 1, 1922, under its formal control as well.

The next year the universally admired Quex Sinclair rose from director of naval intelligence to chief of the Secret Intelligence Service (S.I.S.)—“C,” in the official hieroglyph. The Foreign Office agreed to let him assign G.C.&C.S. its work while it administered the agency. Soon after he took over, G.C.&C.S., which had been housed first behind the Charing Cross railroad station and next in distant quarters in Kensington, moved in 1925 into the third and fourth floors of the ten-story gray concrete Broadway Buildings. The office building, at 54 Broadway, a couple of blocks from Westminster Abbey, and housing as well the S.I.S., was a few hundred yards from the Foreign Office, which codebreakers visited an average of eight times a day, and only a little farther from the Admiralty. G.C.&C.S. expanded by 1935 to about 90 employees, 30 of them cryptologists, and by mid-1939 to 200, with 33 cryptologists. In addition, between 140 and 240 servicemen were intercepting foreign transmissions. Thus, by 1939, almost 500 persons worked in British cryptology at an annual salary cost of
£
100,000 (or about $3 million in 1991 dollars).

The armed services provided not only the intercept personnel but the intercept posts themselves. Economics compelled cooperation. The War Office handled the Middle East; the Admiralty, the Far East; the Air Ministry picked up what it could hear within the United Kingdom. The need to centralize interception, traffic analysis, and cryptanalysis under one roof largely withstood the centrifugal
pulls of the different services to withdraw elements from G.C.&C.S. or establish their own duplicative bodies.

Like all agencies, G.C.&C.S. continually reorganized itself. Early in 1924 one of the more important of the Room 40 recruits, the prickly lawyer William F. (Nobby) Clarke, whose principal interest was naval cryptanalysis, was on vacation near Nice when a suicide in G.C.&C.S. opened up a senior assistant’s slot. Denniston promoted one of his prewar friends who had been a subordinate of Clarke’s in Room 40 and whose work, Clarke thought, although good, had not been outstanding. Clarke was furious. Denniston explained upon Clarke’s return that Sinclair had not chosen Clarke because Clarke was too busy on Admiralty assignments, among them lecturing to naval officers on cryptology to impress upon them the lessons of the war. The codebreaker protested violently that if his naval work was prejudicing any promotion, he wanted to be relieved of it. This put Denniston in a difficult position, as there was no one else capable of doing it. To Clarke’s surprise, Sinclair invited him to a private lunch at his home.

No junior [assistant] had ever had that pleasure, pleasure it was, for he was an excellent host [Clarke wrote]. I was the only guest, another change, and it was soon clear that I had been asked because he was anxious to hear my views. These I gave quite frankly and emphasized the importance of the naval side of our work and the vital necessity, in my opinion, of having a proper naval section; he listened, as he always did, most attentively, asking his usual searching questions and said he would think the matter over. Soon afterwards Denniston saw me, said the formation of a naval section had been decided on, that I was to be its head and that I would be promoted at once. This duly took place about the middle of 1924.

The Naval Section attacked the cryptosystems of foreign navies, while most of G.C.&C.S. concentrated on diplomatic solutions. In 1930, the Army Section was formed and, in 1936, the Air Section.

The most important cryptanalyst was Knox. In 1920, he had married a Room 40 assistant, Olive Roddam, and a year later, after selling most of his Great Western Railway stock, bought a damp, chilly, drafty house on 40 acres of woodland near High Wycombe, half an hour northwest of London. The cryptanalyst commuted to work by train, like his stockbroker neighbors, and in the coaches examined photographs of the papyrus rolls of the dramatist Herodas. In 1922, Cambridge University Press published the restored text of Herodas’s mimes and their English translation, with Knox as editor and with notes by his former classics tutor. Much of the book’s 465 pages consisted of densely printed commentary, mainly on Greek and Latin syntax and vocabulary. Because of the edition of Herodas and another contribution to classical scholarship, Knox was invited to become professor of Greek at Leeds University. But he turned it down, perhaps with regret.

He regarded his suburban neighbors with a certain cynicism: he was surprised at the prevalence of adultery when all the wives looked so much alike. But he played tennis with them, spinning the ball almost unreturnably. He bought a motorcycle for commuting as soon as he no longer had to study Herodas on the train; in 1931, he had the inevitable accident: he broke his leg, which left him with a slight limp. At about that time, frustrated by his work and yearning to return to Cambridge, he was kept from quitting by his wife’s reminding him of his duty to educate his sons and of the national importance of his work. This he carried out in a chaotic office at Broadway Buildings at hours that defied Foreign Office routine: he arrived early in the morning and departed at 4
P.M
. He seemed to live on black coffee and chocolate.

Knox and his colleagues enjoyed fair success in those glory years of codebreaking. With Strachey and Clarke, Knox focused at first on the all-important American codes. Most posed few obstacles, and those that did, such as a superenciphered code introduced after the end of World War I, were solved after not too great a delay. Knox also
successfully tackled Hungarian codes. A former czarist cryptanalyst, E. C. Fetterlein, tall, stolid, whose index finger was adorned with a large ruby given him for his successes in the years before the overthrow of Nicholas II, read Soviet Communist cryptograms with great panache—until his work was nullified in 1927 by deliberate exposure of the intercepts for political reasons. G.C.&C.S. solved French, Italian, Japanese, and Spanish messages, among others. Every week it distributed between sixty and eighty intercepts, each identified by a six-figure number.

Against only one country’s codes and ciphers did G.C.&C.S. fail: Germany. But it hardly seemed to matter. The former rival had been thoroughly defeated and all but stripped of her armed forces. The Admiralty, concerned more with Japan and America, had little interest in Britain’s former enemy. Technical circumstances further inhibited G.C.&C.S.’s feeble efforts. The German Foreign Office was using the one-time pad, the only theoretically and practically unbreakable cipher. German army radio traffic was hard to intercept in the British Isles. And with almost no German navy at first, there were almost no naval messages to intercept. Moreover, though in 1924 the
Reichsmarine
was still using the
AFB
code—the edition that Room 40 had broken—the difference between wartime and peacetime vocabulary made it difficult to solve messages.

Later, as the German navy gradually revived, studies showed that it was using a machine to encipher messages that first had been encoded in
AFB.
This so discouraged G.C.&C.S. that it stopped intercepting German naval messages altogether. For a decade it ignored
Reichsmarine
traffic. It thus lost the contact that is vital for keeping up with the small modifications that individually can be mastered—as the Poles did with the Enigma keying changes—but that in combination raise too great an obstacle. The five-man Naval Section directed its energies instead to the traffic of the French, Italian, Japanese, Soviet, and American navies.

Then, in July 1936, Spanish General Francisco Franco, fed up with the republican government in Madrid, rose in insurrection. Within days, Fascist Italy and Nazi Germany began sending him weapons. Their troops followed. As the civil war in Spain widened, the Mediterranean swarmed with troop transports, merchant vessels, warships. The ether hummed with messages, many of them Italian. G.C.&C.S. had long ago reconstructed Italy’s main naval code, in large part, Denniston remarked, “because of the delightful Italian habit of encyphering long political leaders [editorials] from the daily press.” These solutions had enabled Britain to track the movements of Italian warships during dictator Benito Mussolini’s invasion of Abyssinia in 1935, which threatened the Mideast bulwark of the very foundation of British power: India. Now the danger was more acute. Mussolini, hostile to Britain after her opposition to his aggression, was calling the Mediterranean
mare nostrum
and trying to make it an Italian lake. Just as his Ethiopian invasion had threatened British-controlled Egypt, the Spanish civil war imperiled Gibraltar, and Britain began to see that for the first time since 1798, she was threatened with being squeezed out of the Mediterranean.

It was in these circumstances that G.C.&C.S. realized that the Italian navy had introduced a cipher machine, soon identified as the commercial Enigma. Knox attacked the problem. The machine, including its rotor wiring, was known to G.C.&C.S., so it did not have to be reconstructed; only the daily keys had to be recovered. And since the commercial model lacked the plugboard of the military version, the problem was simplified. Knox used a technique that everyone who tried to solve rotor messages seems to have hit upon, one that has become known as
la méthode des bâtons
, the rod method, so called from the wooden rods onto which were glued strips of paper with the cipher alphabet of each rotor written on it.

Using the rod method, Knox succeeded in determining the keys for some messages and thus in reading other messages enciphered in that day’s key. He then attacked the messages of the Franco forces and
of the German forces in Spain, which used the commercial Enigma. By 1937, he had succeeded.

These successes, together with the rise in German naval traffic volume with the
Kriegsmarine
’s arrival in some force in the Mediterranean, perhaps gave him hope that he might solve the German naval Enigma. G.C.&C.S. wanted to intercept lower-level messages in the hope of matching them to Enigma messages and so obtaining lengthy cribs, but lack of men and gear prevented this. And though Knox determined that the naval Enigma had a plugboard, he made no further progress.

The increase in international tension led to an important intelligence development within the Royal Navy. After Mussolini’s aggression in 1935, the deputy chief of the naval staff, Admiral William James, became concerned about the ability of the Naval Intelligence Division to cope with an emergency. His concerns were exacerbated during the Spanish civil war by the lack of intelligence about foreign naval forces, particularly submarines, blockading the Republican-held areas. During the last two years of World War I, James had headed Room 40, technically Section 25 of the Naval Intelligence Division, and he knew that it was the lack of coordination between the intelligence and operations divisions that had enabled the German High Seas Fleet to escape at the Battle of Jutland. To avoid a recurrence of that flaw, James proposed a center for intelligence that would directly serve operations. The director of naval intelligence began to plan the expansion of the insignificant movements section of the intelligence division into such a unit. It would collect and evaluate all operational intelligence and disseminate what was needed to the fleet. He assigned the expansion to Paymaster Lieutenant Commander Norman Denning, a round-faced man in his thirties.