Alan Turing: The Enigma (34 page)

This might have meant a certain priority being given to von Neumann’s research areas – at that time in the mathematics associated with quantum mechanics and other areas of theoretical physics, and not including logic or the theory of numbers. On the other hand, a position with von Neumann would be the ideal start to the American academic career, which, presumably, Alan’s father thought wise. Competition was intense, and the market, already in depression, was flooded by European exiles. The stamp of approval from von Neumann would carry great weight.

In
professional terms, this was a big decision. But all Alan wrote of the opportunity to Philip Hall on 26 April was: ‘Eventually a possibility of a job here turned up’, and to Mrs Turing on 17 May ‘I had an offer of a job here as von Neumann’s assistant at $1500 a year but decided not to take it.’ For he had cabled King’s to check that the fellowship had been renewed, and since it had, the decision was clear.

Despite himself, he had made his name in the Emerald City. It was not entirely necessary to have a reputation in order to be listened to. By this time, von Neumann was aware of
Computable Numbers
, even if he had not been a year earlier. For when he travelled with Ulam to Europe in this summer of 1938, he proposed
²⁶
a game of ‘writing down on a piece of paper as big a number as we could, defining it by a method which indeed has something to do with some schemata of Turing’s.’
^*
But whatever the attractions, remunerations and compliments, the real issue was much simpler. He wanted to go home to King’s.

The thesis, which in October he had hoped to finish by Christmas, was delayed. ‘Church made a number of suggestions which resulted in the thesis being expanded to an appalling length.’ A clumsy typist himself, he engaged a professional, who in turn made a mess of it. It was eventually submitted on 17 May. There was an oral examination on 31 May, conducted by Church, Lefschetz and H.F. Bohnenblust. ‘The candidate passed an excellent examination, not only in the special field of mathematical logic, but also in other fields.’ There was a quick test in scientific French and German as well. It was vaguely absurd, to be examined in this way while at the same time he was refereeing the PhD thesis of a Cambridge candidate. This, as it happened, he had to reject. (To Philip Hall on 26 April: ‘I hope my remarks don’t encourage the man to go and rewrite the thing. The difficulty with these people is to find out a really good way of being blunt. However I think I’ve given him something to keep him quiet a long time if he really is going to rewrite it.’) The PhD was granted on 21 June. He made little use of the title, which had no application at Cambridge, and which elsewhere was liable to prompt people to retail their ailments.

His departure from the land of Oz was rather different from that in the fable. The Wizard was not a phoney, and had asked him to stay. While Dorothy had disposed of the Wicked Witch of the West, in his case it was the other way round. Though Princeton was fairly secluded from the orthodox, Teutonic side of America, it shared in a kind of conformity that made him ill at ease. And his problems remained unresolved. He was inwardly confident – but as in the
Murder in the Cathedral
which he saw performed in March (Very much impressed’) he was living and partly living.

In
one way, however, he resembled Dorothy. For all the time, there was something that he could do, and which was just waiting for the opportunity to emerge. On 18 July Alan disembarked at Southampton from the
Normandie
, with the electric multiplier mounted on its breadboard and wrapped up securely with brown paper. ‘Will be seeing you in the middle of July’, he had written to Philip Hall, ‘I also expect to find the back lawn crisscrossed with 8 ft. trenches.’ It had not come to that, but there were more discreet preparations, in which he could take part himself.

Alan was right in thinking that H M Government was concerned with codes and ciphers.
^*
It maintained a department to do the technical work. In 1938 its structure was still a legacy of the Great War, a continuation of the organisation discreetly known as
Room 40
that the Admiralty had set up.

After the initial break of a captured German code book, passed to the Admiralty by Russia in 1914, a great variety of wireless and cable signals had been deciphered by a mostly civilian staff, recruited from universities and schools. The arrangement had the peculiar feature that the director, Admiral Hall, enjoyed control over diplomatic messages (for instance the famous Zimmermann telegram). Hall was no stranger to the exercise of power.
²⁷
It was he who showed Casement’s diary to the press, and there were more important instances of his
²⁸
‘acting on intelligence independently of other departments in matters of policy that lay beyond the concerns of the Admiralty.’ The organisation survived the armistice, but in 1922 the Foreign Office succeeded in detaching it from the Admiralty. By then it had been renamed as the ‘Government Code and Cypher School’, and was supposed to study
²⁹
‘the methods of cypher communication used by foreign powers’ and to ‘advise on the security of British codes and cyphers.’ It now came technically under the control of the head of the secret service,
^†
himself nominally responsible to the Foreign Secretary.

The director of GC and CS, Commander Alastair Denniston, was allowed by the Treasury to employ thirty civilian Assistants,
³⁰
as the high-level staff were called, and about fifty clerks and typists. For technical civil service reasons, there were fifteen Senior and fifteen Junior Assistants. The Senior Assistants had all served in Room 40, except perhaps Feterlain, an exile from Russia who became head of the Russian section. There was Oliver Strachey, who was brother of Lytton Strachey and husband of Ray Strachey, the well-known feminist, and there was Dillwyn Knox, the classical scholar and Fellow of Kings until the Great War. Strachey and Knox had both been members of the Keynesian circle at its Edwardian peak. The Junior Assistants had been recruited as the department expanded a little in the 1920s; the most recently appointed of them, A.M. Kendrick, had joined in 1932.

The
work of GC and CS had played an important part in the politics of the 1920s. Russian intercepts leaked to the press helped to bring down the Labour government in 1924. But in protecting the British Empire from a revived Germany, the Code and Cypher School was less vigorous. There was a good deal of sucess in reading the communications of Italy and Japan, but the official history
³¹
was to describe it as ‘unfortunate’ that ‘despite the growing effort applied at GC and CS to military work after 1936, so little attention was devoted to the German problem.’

One underlying reason for this was economic. Denniston had to plead for an increase in staff to match the military activity in the Mediterranean. In the autumn of 1935, the Treasury allowed an increase of thirteen clerks, although only on a temporary basis of six months at a time. It was a typical communication
³²
from Denniston to the Treasury in January 1937 that read:

The situation in Spain … remains so uncertain that there is an actual increase in traffic to be handled since the height of the Ethiopian crisis, the figures for cables handled during the last three months of 1934, 1935 and 1936 being

During the past month the existing staff has only been able to cope with the increase in traffic by working overtime.

During 1937, the Treasury agreed to an increase in the permanent staff. But this measure did not meet a situation in which:
³³

The volume of German wireless transmissions … was increasing; it was steadily becoming less difficult to intercept them at British stations; yet even in 1939, for lack of sets and operators, by no means all German Service communications were being intercepted. Nor was all intercepted traffic being studied. Until 1937-38 no addition was made to the civilian staff as opposed to the service personnel at GC and CS; and because of the continuing shortage of German intercepts, the eight graduates then recruited were largely absorbed by the same growing burden of Japanese and Italian work that had led to expansion of the Service sections.

It
was not simply a question of numbers and budgets, however. This elderly department was failing to rise to the mechanical challenge of the late 1930s. The years after the First World War had been ‘the golden age of modern diplomatic codebreaking’.
³⁴
But now the German communications presented GC and CS with a problem beyond their powers – the Enigma machine:
³⁵

By 1937 it was established that, unlike their Japanese and Italian counterparts, the German Army, the German Navy and probably the Air Force, together with other state organisations like the railways and the SS used, for all except their tactical communications, different versions of the same cypher system – the Enigma machine which had been put on the market in the 1920s but which the Germans had rendered more secure by progressive modifications. In 1937 GC and CS broke into the less modified and less secure model of this machine that was being used by the Germans, the Italians and the Spanish nationalist forces. But apart from this the Enigma still resisted attack, and it seemed likely that it would continue to do so.

The Enigma machine was the central problem that confronted British Intelligence in 1938. But they believed it was unsolvable. Within the existing system, perhaps it was. In particular, this department of classicists, a sort of secret shadow of King’s down in Broadway Buildings, did not include a mathematician.

No addition was made to permanent staff in 1938 to meet this striking deficiency. But
³⁶
‘plans were made to take on some 60 more cryptanalysts in the event of war.’ And this was where Alan Turing came into the story, for he was one of the recruits. He might possibly have been in touch with the government since 1936. Or he might have stepped off the
Normandie
with the intention of demonstrating his multiplier. But more likely he was suggested to Denniston through one of the elder dons who had worked in Room 40 in the First World War. One of these was Professor Adcock, a Fellow of King’s since 1911. Had Alan ever spoken of codes and ciphers on the King’s High Table, his enthusiasm could quickly have been communicated to GC and CS. One way or another, he was a natural recruit. On his return in the summer of 1938, he was taken on to a course at the GC and CS headquarters.

Alan and his friends could see that war was likely, despite all the hopes of 1933, and found it important to see that they were used in some sensible way, rather than in leading cannon-fodder over the top. It was hard to separate this feeling from that of wanting to avoid injury, and the government’s policy for reserving intellectual talent came as some relief, releasing them from guilt. In this way, Alan Turing made his fateful decision, and chose to begin his long association with the British government. For all his suspicion of ‘HM Government’, it must have been exciting to be allowed to see the back of the shop. But it meant that he had for the first time surrendered a part of his mind, with a promise to keep the government’s secrets.

Though
stern and demanding, the government that he joined, like the White Queen who took Alice on her journey, was in a muddled state, struggling with safety pins and string. The failure to make a serious effort at the Enigma was but one aspect of an incoherent strategy, which all the world could see in September 1938. Until that month, British people could still convince themselves that there were logical ‘solutions’ to German ‘grievances’ within the existing framework. After that month, moral debates about fairness and self-determination finally ceased to cloak the essential reality of power. The Cambridge population re-assembled for what was to be ‘the year under the terror’ in the words of Frank Lucas, a King’s don. The White Queen had squealed before the prick of the needle actually came. London children had been evacuated to Newnham College, and the male undergraduates had felt themselves on the brink of enlistment. Nothing was clear, but that something dreadful was in the offing. Radical agitation emphasised the devastating power expected of the modern air raid, while the government seemed to have nothing in mind but the building of bombers to execute a counter-attack.

The old world might be nearing its end, but there was a little escape into fantasy on offer from the new.
Snow White and the Seven Dwarfs
arrived at Cambridge in October, and Alan played exactly the part expected by Cambridge of King’s dons by going to see it with David Champernowne. He was very taken with the scene where the Wicked Witch dangled an apple on a string into a boiling brew of poison, muttering

Dip the apple in the brew
Let the Sleeping Death seep through

He liked to chant the prophetic couplet over and over again.

Alan also invited Shaun Wylie over from Oxford as guest at the college feast. Shaun Wylie and David Champernowne had been fellow scholars at Winchester. Alan had mentioned the multiplying cipher idea to Champ, but he told Shaun about the summer course, saying that he had put his name forward to the authorities as a possible recruit. The Princeton treasure hunts therefore had a serious consequence. He also said that he had been studying probability theory, and would like to experiment with tossing coins, but would feel silly if someone came in, although in King’s he need hardly have worried about appearing eccentric. They also played war games. David Champernowne had ‘Denis Wheatley’s exciting new war game – Invasion’, for which they invented new rules to make it a better game. Maurice Pryce, then in his second year as a university lecturer, had a conversation with Alan about the new idea of uranium fission, and Maurice found an equation for the conditions required for a chain reaction to start.
^*