Share This Article

There was no normal way to become a code breaker in World War II; everyone who landed in the job arrived there more or less by accident. Some recruits to Britain’s code-breaking establishment remembered being asked a few haphazard questions about whether they had studied the classics, or played chess, or liked to do crossword puzzles. And there was the inevitable old-boy network that favored graduates of Oxford and Cambridge, but that was as systematic as things got. No one really knew what mysterious combination of skill, background, and mental habits it took to be a success at this strange occupation.

John Tiltman was the accidental cryptanalyst par excellence. His clipped mustache and regimental bearing made him look like a British colonel from central casting—“every inch a soldier,” friends said. Severely wounded at the Battle of the Somme in World War I and awarded the Military Cross for his exploits, Tiltman was given a desk job to recuperate. And so, totally by fluke, he found himself in the small postwar bureau of code breakers that would soon go by the rather unimaginative cover name of the Government Code & Cypher School (GC&CS).

Tiltman said years later that he’d had no knowledge of higher mathematics, statistics, or probability, nor was he a natural linguist. He was not even a college graduate: though offered a place at Oxford at the astonishing age of 13, he turned it down when his family went broke after his father’s sudden death. But Tiltman—and his superiors at GC&CS—discovered almost immediately that he had a certain indefinable knack for sensing patterns, combined with indefatigable tenacity.

Within a year of his initiation into this secret world Tiltman was on his way to Simla, in the Himalayan foothills of British India, with the assignment of breaking coded Soviet diplomatic traffic passing between Moscow, Kabul, and Tashkent. The messages that Tiltman deciphered there throughout the 1920s—a feat made all the more remarkable for his only rudimentary knowledge of Russian—revealed a concerted effort by Moscow to foment anti-British feeling and subversion along the frontier of the Raj.

In the huge expansion of GC&CS that the war would bring, many of Tiltman’s old-school colleagues were left by the wayside; advanced coding systems like the German Enigma machine had transformed cryptanalysis from intuitive art to complex mathematical science, as punch cards, the first electronic computers, and staffs of thousands took the place of lone brilliance. But Tiltman, always working by himself—“much more like a detective” than a modern cryptanalyst, said one of his more modern, and mathematically inclined, colleagues—made breakthrough after breakthrough in cracking the most vital Axis codes of the war.

In July 1940, Tiltman spotted several messages sent with near-identical settings of the Enigma machine used by the German railways, a break which laid bare the machine’s inner workings. The following March, deciphered railway Enigma messages pointed to Nazi preparations for a surprise attack on the Soviet Union.

In the first year of the war, in the Victorian country mansion that GC&CS had taken over as its headquarters, working in an upstairs room that had once been the nursery and was still adorned with Peter Rabbit wallpaper, Tiltman broke ciphers used by the German SS and police, which would provide the first confirmation of the Nazis’ extermination program.

And in 1941 Tiltman made an almost magical discovery that led to the solution of the most mathematically complex cipher system of the entire war, the German teleprinter code. In the anxious weeks leading up to D-Day, decoded teleprinter traffic would provide confirmation that the Germans had been taken in by the Allies’ deception plan, designed to conceal where the landings would take place. By that time, the world’s first digital electronic computer, a behemoth with 2,500 vacuum tubes, was breaking the daily stream of messages. But it was Tiltman’s discovery— his decoding, by hand, of two ever-so-slightly-different messages erroneously sent by a German cipher clerk using the same setting of the machine—that provided the crucial breakthrough.

Often wearing the regimental purple-and-green tartan trews of the King’s Own Scottish Borderers, standing at a specially made desk, cutting and endlessly rearranging message texts on strips of paper, following leads for days and weeks on end, always modestly dismissing his successes as hunches that worked out, Tiltman had the distinction of being not only the last of the great old-school code breakers, but probably the greatest as well.


Originally published in the November 2008 issue of World War II Magazine. To subscribe, click here