Enigma was the mechanical cipher machine invented at the end of World War I by the German electrical engineer Arthur Scherbius, used for communication by the army units of Nazi Germany during World War II. Calculating and deciphering the codes encrypted by this machine was nearly impossible until the English mathematician, cryptanalyst, computer scientist, logician, philosopher, and theoretical biologist Alan Turing developed a cryptanalytic process called Banburismus at Bletchley Park. This allowed him to crack Enigma’s codes by inventing the code-breaker machine, the Bombe. This article will describe how deciphering the Enigma codes ultimately contributed to changing the course of World War II, and led to the defeat of the Nazis.
A man holds up a newspaper with the headline "Nazis Quit!" amid celebrations (1945). Bettan/Getty Images
After the National Socialist German Workers' Party took over the administration, the German army started to take up arms, first secretly and then openly. While the Germans were preparing for a new war, the remaining powerful countries of Europe, such as France and the United Kingdom, followed a peaceful path to avoid being involved, after the devastating effects of World War I. However, this peaceful approach from the European states was interpreted by Nazi Germany as their weakness. Having been left behind in the arms race, Poland, France, and the United Kingdom were powerless against Nazi Germany (Britannica, 2021). Cracking the codes of the Nazi's encrypted communication machine, Enigma, was crucial to the Allies' cause. By deciphering Enigma, they were able to learn crucial information, such as the numbers and locations of the German forces, as well as their war strategy. With this information, they were ultimately able to successfully use their limited power against the Nazis.
Portrait of Alan Turing (1912-54). Image: Science Photo Library
The British mathematics professor and cryptanalyst Alan Turing was only twenty-seven when he was accepted for the position of decrypting Enigma at Bletchley Radio Manufacturing (O'Connor & Robertson, 2003). Turing believed that the Enigma algorithm was not an encryption that the human brain could decipher. Enigma took each letter as input and applied a random replacement to output the ciphertext, just like any other encryption machine. In this case, all encryption machines are predictable and repeatable.
The feature that distinguished Enigma from other devices was the size of the key setting: the point was not to create ciphers that could never be deciphered, but to delay its decryption as much as possible by using identical machines that resulted in complex setting modifiers with a wide key setting. Enigma was working with a wheel-operated rotary mechanism: a completely new letter was defined for each letter as the wheel was rotated. The Nazis continued to expand the key settings to strengthen Enigma throughout the war. Therefore, even if the enemy had a copy of Enigma, it was almost impossible to find the appropriate key setting among thousands of them, as the key setting was expanding day by day (Ashish, 2022). According to Turing, only another machine could decode a code encrypted by Enigma. Based on this thought, he invented the code-breaking machine called Bombe.
Turing was not the first person to attempt to create a code-breaker machine to crack Enigma. The Polish mathematicians Langer, Ciężki, and Rejewski discovered that a panel added to the front of Enigma was altered by the settings, and thanks to this information, they built a code-breaker machine called Bomba. However, they still could not tell how Enigma was wired (Baker, 2018). Bomba was not fast enough to read the messages from all the key settings that Enigma had. Therefore, Turing re-engineered the Polish Bomba, and in March 1940 he created the Bombe, a more advanced and faster version of its predecessor. Although the decoder had to guess a few words in the message to start the process, Bombe translated the coded letters into plain German (Copeland, 2019).
Lord, B. (2005), Enigma Machine. Wikipedia.
There were two main reasons why Enigma could be decrypted. The first was that the German intelligence had started to give daily messages on the same key setting repeatedly, rather than giving them on a random key setting. These iterations narrowed the key space, and made it easier for Bombe to find the cyphered letters at a faster rate, as it did not have to search for all the key settings. The second was an oversight on the part of German engineers. Enigma was not outputting the same letter that was entered in any key setting. For example, when the letter A was input, any letter other than A was encrypted as the output. Engineers thought that encoding an entered letter as any letter other than itself would make Enigma more secure. However, this regulation made the input letter easier to find (Ashish, 2022).
Deciphering the Enigma was a turning point in World War II since it allowed the allies to decipher the Nazis' war strategies. This ultimately allowed them to defeat the German army by utilizing the information of where and when they would strike. For the Germans not to realize that the Enigma had been deciphered, the UK allowed the Germans to gain the upper hand in military confrontations for a short while. However, they gradually routed the German troops and won the war. The Nazis entered a period of decline after the code was broken, as all of the state secrets and war tactics passed between them were followed and known by their enemies. Therefore, the duration of the war was significantly shortened, and many lives were saved. Given this, it is clear that the deciphering of Enigma was one of the main reasons for the defeat of the Nazis in World War II.
Baker, J. (2018). Forgotten heroes of the Enigma story. Nature. Retrieved February 17, 2022, from: https://www.nature.com/articles/d41586-018-06149-y
Copeland, BJ. (2019). Ultra. Allied Intelligence Project. Britannica. Retrieved February 17, 2022, from: https://www.britannica.com/topic/Ultra-Allied-intelligence-project#ref1073435
Britannica (n. d.). Forces and resources of the European combatants, 1939. Britannica. Retrieved Februrary 17, 2022 from:
O'Connor, JJ. Robertson, EF. (2003). Alan Mathison Turing. Mac Tutor. Retrieved February 17, 2022, from:
Ashish. (2022). The Imitation Game: How Did The Enigma Machine Work? Science ABC. Retrieved February 17, 2022, from:
Ashish. (2022). Cracking the Uncrackable: How Did Alan Turing and His Team Crack The Enigma Code? Science ABC. Retrieved February 17, 2022, from:
Ochs, M. (1945). A man holds up a newspaper with the headline "Nazis Quit!" amid celebrations. Bettman/Getty Images. Retrieved from: https://www.businessinsider.com/historical-photos-show-victory-celebrations-following-end-of-wwii-europe-2020-4#news-of-victory-spread-fast-as-newspapers-ran-big-headlines-like-nazis-give-up-and-nazis-quit-1
Science Photo Library (n.d.). Portrait of Alan Turning (1912-54), The Engineer. Retrieved from: https://www.theengineer.co.uk/late-great-engineers-alan-turing/
Lord, B. (2005) Enigma Machine. Wikipedia. Retrieved from: https://tr.m.wikipedia.org/wiki/Dosya:Enigma-plugboard.jpg
Fykse Helge (n. d.). [German forces working next to the Enigma Machine]. DefenceMediaNetwork. Retrieved from: https://www.defensemedianetwork.com/stories/when-telford-taylor-and-u-s-army-g-2-gained-access-to-ultra/
For further reference, here is a video illustrating how Enigma worked: