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Alan Turing at VE Day

an article by Andrew Hodges (1995)
for the (London) Sunday Times,
on the fiftieth anniversary of VE Day.

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A hippy; that was how people who lived for another twenty years would describe him. At the time, they called him Prof. Partly for being the cartoonist's eccentric professor, partly for having an answer to almost everything. But he was no professor; he was only 32 and looked younger; he was hardly known outside Cambridge, which had not given him even a lectureship; he was wild-haired, bright-eyed, dirty-fingered, awkward-mannered, and tie-less. He emanated sometimes subtly camp asides, sometimes grating high-pitched laughter; but was also a strong-legged marathon runner; direct and forceful when he chose. This was Alan Turing on the night of 8 May 1945, by the victory bonfire in north Buckinghamshire.

'The war's over now, you can tell all', said the young electronic engineer who had been working with him since March 1944. He meant it as a joke, but Alan Turing snapped back and shut him up, and in fact the work he had done at Bletchley Park remained shut up for another thirty years. He was far from alone: thousands of young people said farewell to these years of their lives and never spoke of them until old age. Many of them had only a fragment of knowledge about what was going on at Bletchley Park, the breaking of enemy codes and ciphers. But there were a few who knew the whole picture, and one of those was the Prof.

At its surrender the German submarine fleet was still a formidable force, still with bases in Norway. Tremendous resources had been poured into launching new U-boats even in the spring of 1945. And yet it had posed no serious threat to Allied victory. There was a reason for this, which Doenitz never suspected but which the unmilitary Prof, cycling in shabby sports jacket through the Buckinghamshire countryside, knew very well. Since the spring of 1943 the German naval communications had been an open book to the Anglo-American forces. Their cipher system had been completely mastered. Every U-boat could be tracked, avoided, destroyed. Information was king in the submarine war, and the last-ditch ship-building, the courage of Das Boot,  the ruthlessless of Nazi industrial slavery — all were useless against Allied control of the war of intelligence.

It had begun very differently. In 1938 the British and French codebreakers were stumped by the Enigma cipher on which all German military signals were encoded. Two things changed this. First, the British government at last conceded the existence of science, and recruited its first mathematician, Alan Turing. He began part-time work from September 1938. Secondly, in July 1939 the British and French received as a gift the brilliant work done by Polish mathematicians, which transformed the situation. Turing and a growing group of mathematical recruits, based at Bletchley Park after September 1939, developed the Polish ideas.

The Poles had managed to find out exactly how the German ciper machine, the Enigma, worked. But this was never enough. To break the code one had to know the keys, the complicated schemes for the operators of the machine to follow. They had invented brilliant methods that worked with certain schemes that had been used, but these kept changing. In mid-1940 Alan Turing saw a wonderful idea, exploiting the logic of the Enigma machine, which yielded a powerful attack into the new German key-systems. This, embodied in a new machine, soon allowed decoding of the Luftwaffe signals. In 1941 Turing broke into the much more complex system used by the U-boats. He devised quite new scientific methods for extracting the keys. Soon Bletchley Park was running most sophisticated information processing ever conceived.

The British system had proved itself flexible and imaginative enough to think on a big scale, equivalent to marshalling the entire talent of its universities, barriers of age and sex and background overriden, able to adapt rapidly to the changes as they came in the German systems. It was a miracle but a well-organised miracle. It was the 1960s ahead of time in its cooperative informality, its range and versatility of scientific ideas. But it could not perform magic: in February 1942 a small change was made in the U-boat Enigma machine, and overnight the codebreakers became powerless.

During that year, Allied ships were sunk in unsustainable numbers. Turing went to the United States in November 1942 for a top-level combined assault on the problem. Then, a German oversight, exploited by brilliant Bletchley ingenuity, allowed resumption of regular code-breaking as 1943 began. Air cover, convoys, and radar improvements rested upon the Enigma information as the crucial element: they knew where the U-boats were. From then to victory, Bletchley Park produced every day the equivalent of a newspaper full of nothing but explicit details of U-boat commands and reports. This was the silent background to the Allied assault on Europe.

And yet, if asked on VE Day what was his most important work, the Prof would have pointed to something much earlier: entirely original ideas he discovered when only 23. He had created the concept now called the Turing machine, which shook up the foundation of mathematical analysis and connected it in a completely original way with the philosophy of Mind. To the Prof as a mathematician the Second World War was a temporary problem: his earlier work was part of the timeless. In 1945 this was little known, even to mathematicians: it was buried in the arcane area of mathematical logic. But the Prof knew it, and he was about to use it to spring a surprise on the world.

For Turing was not a pure mathematician alone: these abstract ideas had given him practical ideas about codes in 1936, and he began even then pondering on the implications for the coming war with Germany. At Bletchley Park, the stunningly successful mechanization of logical methods gave him ideas for what we can now recognise as a new industrial revolution, the information age. And so Turing was not resting on secret laurels as the U-boats surrendered. He had already moved on from Bletchley Park. The bonfire night found him elsewhere: at Hanslope Park, another secret site to the north, where he was not concerned about the war but with the future. He was there to learn about digital electronics with a definite aim in mind: designing the first electronic computer .

Words change their meaning: in 1945 a 'computer' was a person doing calculations, or any machine doing a calculation. Nowadays we use that word in a more particular sense: a machine which can be made to handle anything, whether accountancy, graphic design, Internet, or word processing, just by inserting different programs. One machine, whose hardware is left untouched: a universal machine. Such machines were unknown in the Second World War. Amazing as it is now, Bletchley Park managed by engineering new machines for each new codebreaking method. The Prof, however, knew there was a better way.

Wrapped up in Alan Turing's abstract work in 1936 was just that idea of a universal  machine, able to do any computation, by the reading and execution of programs as familiar today. But it needed logical operations of very high speed to make his idea one of practical use. That was where electronics came in. For in 1945, to Turing and a tiny few at Bletchley Park, in uttermost secrecy, electronics meant something new, something beyond radio and radar. The problem of breaking the special messages sent at the highest German levels, had called for calculations, at electronic speeds. This had brought about the building of an unprecedented large electronic machine, called the Colossus, brought into action just before D-Day. This was not a computer in sense of a universal machine, as it was designed specifically for breaking the special cipher. But it was a British engineering triumph, showing that large-scale digital electronics could work.

Electronic speed was the key ingredient needed and seized upon by the Prof. He combined the abstract universal machine of his 1936 work, and the electronic speed of the 1944 Colossus, to plan the modern computer. VE Day meant the coming of freedom and the opportunity to try this out in practice: VE Day was the interface between the pre- and post-computer world. This was Turing's vision: this was his big surprise, his public gift, for the world of 1945.

Alan Turing was not alone with the idea of the universal machine made real by electronics. In America, a machine roughly parallel to the Colossus had also sparked the same idea for an electronic computer. In fact the Hungarian-American mathematician John von Neumann dated his first program, the first ever written for the machine he planned, on 8 May 1945. But only Turing saw and promoted the full logical power of the computer. Von Neumann's 1945 designs were successful but based on a limited number-crunching paradigm. Turing was years ahead in seeing applications of all kinds, imagining languages for writing software, sketching out prospects for Artificial Intelligence. Only fifty years later can we see with Turing's vision. Bletchley Park is now at last open to the public, and at the same time, the penetration of cheap computing has made public the world he launched.

Alan Turing had applied his mind to codes since 1936, had been his country's backroom boy through to the end, and was bursting with ideas for the peace. What happened? Turing's computer design was taken on board by the government at the National Physical Laboratory — but scaled down, taken slowly, and overtaken by others. He lost patience; he resigned. His advanced ideas were lost; and so there was no civil legacy of Bletchley Park, no pioneering British software engineering centre for the new world. And Turing never saw the 1960s, although, twenty years ahead again, his 1950s work in mathematical biology, decoding the growth of living things with computer methods, anticipated the 1970s.

For there were other, less tangible, aspects to VE Day. The war fought in the name of freedom let more than one genie out of the bottle: questioning of authority, barriers of class and age, and sexual taboos. As it happened, Alan Turing had found Bletchley a sexual desert. 'You didn't miss anything,' was his description to a gay friend. But he made up for lost time, and the twenty-years-early hippy turned into a open gay man twenty years before Gay Liberation. In 1952 he was arrested. He was obliged to undergo treatment with hormones as chemical castration for a year, to avoid prison. Until then he had continued secret work for GCHQ, as the codebreaking establishment became; this ended when he was deemed, as a homosexual, a security risk. He found himself under watch. Ten years and a day after the landing in Normandy, he died by his own hand.

Andrew Hodges, March 28 1995
for the Sunday Times  of 7 May 1995.

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