I decided to take on the problem of German naval Enigma because no one was doing anything about it and I could have it to myself. In December 1939 I solved part of the naval indicator system, which was very complex. On the same night I also thought of the idea of Banburismus, a technique to help breaking the naval enigma, though I was not sure it would work in practice, and was not in fact sure until somedays had actually broken. For this I invented a device called the Ban, which measured weight. 
I traveled to the United States in November of 1942 and worked with the US Navy cryptanalysis on Naval Enigma and bombe making in Washington. I visited their Computing Machine Laboratory at Dayton, Ohio and I was far from enthusiastic:

It seems a pity for them to go out of their way to build a machine to do all this stopping if not necessary. I am now converted to the extent of thinking that starting from scratch on the design of a Bombe, this method is about as good as our own The American Bombe program was to produce 336 bombes, one for each wheel order. I used to smile inwardly at the conception of test of commutators can hardly be considered conclusive as they were not testing for the bounce with electronic stop finding devices. 
 

From 1945 to 1947, I lived in Richmond, London while I worked on the design of the Automatic Computing Engine (ACE) at the National Physical Laboratory. On February 19 1946 I presented my design of a stored-program computer. In the late 1947 I returned to Cambridge for a year where I worked on Intelligent Machinery. While I was at Cambridge the Pilot ACE was being built, and it's first program was started on May 10, 1950.  
In 1948 I was appointed Reader in the Mathematics Department at the University of Manchester. In 1949 I became Deputy Director at the Computing Laboratory there, working on software for the earliest stored program computers, the Manchester Mark 1. In "Computing machinery and intelligence" I talked about the problem of artificial intelligence, and made an experiment which became known as the Turing Test. My idea was that a computer could be said to "think",  if a human could not tell it apart through conversation, from another human. 

From September 1938, I had been working part time at the GC&CS , the british code breaking organization. I worked on the cryptanalysis of the Enigma with Dilly Knox, a senior code breaker.  After the July 139, Warsaw meeting with the Polish Cypher Bureau provided details of writing the Enigma rotors. I and Knox started to work on a new approach to the problem. 
On September 4, 1939,   the day after the UK declared war on Germany, I went back to Bletchley Park.
Some of the cryptanalytic advances I made during the war were:

• the bombe
  
• deducing the indicator procedure used by the German navy
  
• make a strategy for making much more efficient use of the bombes dubbed Banburismus
  
• developing a way for working out the cam settings of the wheels of the Lorenz SZ 40/42 (Tunny) dubbed Turingery
  
• the development of a portable secure voice scrambler
  

In 1936, I went to Princeton University in America. Here I studied in mathematics and also built three of four stages of an electro mechanical binary multiplier. In June 1938 I got my PhD from Princeton. I returned to Britain soon after.
During World War II I began to work secretly part-time for the British cryptanalytic department, the Government Code and Cypher School, at Bletchley Park. The GC&CS was Britain's code breaking center. When the outbreak of the war started I took up full-time work at it's headquarters. For a time I was head of Hut 8, the section responsible for German naval cryptanalysis. 

I studied mathematics at  Cambridge University. At Cambridge I gained my first class honors in mathematics  After going to school there, eventually I taught at the school. There I worked in quantum mechanics. It was at Cambridge that I developed  proof that automatic computation could not solve all mathematical problems. This concept was called the Turing machine, and is known for the modern theory of computation.