Next week the movie Imitation Game will be released. British mathematician, logician and cryptanalyst Alan Turing was a key figure in cracking the code used by Nazi Germany that helped the Allies win World War II. The British-American movie stars Benedict Cumberbatch, as Turing and Keira Knightley, as Joan Clarke, Turing’s fiancé and fellow code breaker.
The Enigma machine was used to encipher and decipher messages. It was invented by German engineer Arthur Scherbius at the end of World War I. The Enigma allowed an operator to type a message, then scramble it using three to five notched rotors. The receiver needed to know the settings of these rotors in order to decipher the coded text. The leaders of the German army during World War II were so confident that the code they developed could not be broken that they sent most messages using Enigma.
Top mathematicians and general problem solvers were recruited by the Allies, and early computers, known as bombes, were built to uncover the Enigma’s secret settings. The initial design of the bombe was produced in 1939 at the UK Government Code and Cypher School at Bletchley Park by Alan Turing. This episode is a major part of Imitation Game.
Although Bletchley Park was located in England, information gathered there was shared with commanders of Allied forces around the world. On April 17, 1945, Marshall wrote a memorandum for President Truman to which he attached summaries of top secret information based on a deciphered German message dated April 13. The message ordered the “ruthless use of flooding for the defense of Fortress Holland.” Marshall expressed his concern about the inhabitants of German-occupied Holland to the President. He was also concerned about possible starvation of the Dutch residents as well as the future ability of farmers to cultivate their fields.
The three-rotor Enigma machine, shown right, is located at the George C. Marshall Foundation archive.