75 years ago, on January 17, 1940, Polish mathematician Marian Rejewski broke Enigma, the “unbreakable” German cipher machine, for the first time during the World War II. Earlier, simpler versions of Enigma were broken before the war, for the first time in 1932 by the same team of Polish mathematicians: Marian Rejewski, Henryk Zygalski, and Jerzy Różycki.
This multi-national effort started with French intelligence delivering initial materials and culminated in Bletchley Park in England, were the team of mathematicians, including Alan Turing, worked continuously on breaking new enhancements and variants of Enigma being introduced by Germans.
The story of cryptography in WWII is also the story of how first computers came to being. In 1934/35 Rejewski designed first electro-mechanical “cyclometer” to aid in code breaking, then in 1938 he invented more complicated “bomba kryptograficzna”. Alan Turin then significantly expanded the design, based on more general principles, and in 1939 built faster and more capable “British Bombe”. Then in 1943 Americans came with “US Navy Bombe”, which was easier to manufacture and much faster in operations, but it was still electro-mechanical. A full-electronic version was considered by Americans, but apparently shelfed. In the same Bletchley Park that Alan Turing, Polish mathematicians, and others worked on Enigma, another team of cryptographers in 1944 built Colossus that operated on vacuum tubes – now considered the first electronic computer… Read more on Wikipedia.