How old was Alan Turing when he cracked the Enigma Code?

Alan Mathison Turing was born June 23, 1912. He was a brilliant mathematician and logician and studied at both Cambridge, graduating in 1934, and Princeton university, where he received his doctorate, studying mathematics and cryptology. He was working part-time for the British Government’s Code and Cypher School before World War Two broke out.

In 1939, Turing took up a full-time role at Bletchley Park in Buckinghamshire – where top secret work was carried out to decipher the military codes used by Germany and its allies. The main focus of Turing’s work at Bletchley was in cracking the ‘Enigma’ code. The Enigma was a type of enciphering machine used by the German armed forces to send messages securely. The Enigma machine, invented in 1919 by Hugo Koch, a Dutchman, looked like a typewriter and was originally used for business purposes. The German army adapted the machine for wartime use and considered its encoding system unbreakable. They were wrong. The Brits had broken their first Enigma code as early as the German invasion of Poland and had intercepted virtually every message sent through the occupation of Holland and France. 

Although Polish mathematicians had worked out how to read Enigma messages and had shared this information with the British, the Germans increased its security at the onset of war by changing the cipher system every day at midnight. This made the task of understanding the code even more difficult.

During the autumn of 1939 and the spring of 1940, Turing, age 27, along with fellow code-breaker Gordon Welchman and others designed a code-breaking machine known as the Bombe. This device helped to significantly reduce the work of the code-breakers. From mid-1940, German Air Force signals were being read at Bletchley and the intelligence gained from them greatly helped the war effort. July 9, 1941 cryptologists broke the secret code used by the German army to direct ground-to-air operations on the Eastern front.

Turing also worked to decrypt the more complex German naval communications that had defeated many others at Bletchley. German U-boats were responsible for heavy losses on Allied ships and the need to understand their signals was crucial. With the help of captured Enigma material, and Turing’s work in developing a technique he called 'Banburismus', the naval Enigma messages were able to be read from 1941.

Turing headed the ‘Hut 8’ team at Bletchley, which carried out cryptanalysis of all German naval signals. This meant Allied convoys could be directed away from the U-boat 'wolf-packs' (apart from during a period in 1942 when the code became unreadable). Turing’s role was pivotal in helping the Allies during the Battle of the Atlantic.

In July 1942, Turing developed a complex code-breaking technique he named ‘Turingery’. This method fed into work by others at Bletchley in understanding the ‘Lorenz’ cipher machine. Lorenz enciphered German strategic messages of high importance: the ability of Bletchley to read these contributed greatly to the Allied war effort.

Turing traveled to the United States in December 1942, to advise U.S. military intelligence in the use of Bombe machines and to share his knowledge of Enigma. While there, he also saw the latest American progress on a top secret speech enciphering system. Turing returned to Bletchley in March 1943, where he continued his work in cryptanalysis. Later in the war, he developed a speech scrambling device which he named ‘Delilah’. In 1945, Turing was awarded an OBE for his wartime work.

In 1936, Turing had invented a hypothetical computing device that came to be known as the ‘universal Turing machine’. After the Second World War ended, he continued his research in this area, building on his earlier work and incorporating all he'd learnt during the war. While working for the National Physical Laboratory (NPL), Turing published a design for the ACE (Automatic Computing Engine), which was arguably the forerunner to the modern computer. The ACE project was not taken forward, however, and he later left the NPL.

The legacy of Alan Turing’s life and work did not fully come to light until long after his death. His impact on computer science has been widely acknowledged: the annual ‘Turing Award’ has been the highest accolade in the industry since 1966. But the work of Bletchley Park – and Turing’s role there in cracking the Enigma code – was kept secret until the 1970s, and the full story was not known until the 1990s. It has been estimated that the efforts of Turing and his fellow code-breakers shortened the war by several years. What is certain is that they saved countless lives and helped to determine the course and outcome of the conflict.