The Enigma machine looked like a typewriter with a plugboard. Press a key and an electrical signal passed through three (later four) rotating cipher wheels, a reflector, and a plugboard swapping letter pairs, producing a substitution so complex that the number of possible settings exceeded 158 million million million. The German military believed it was unbreakable. For most of the 1930s, they were right.
The first cracks came from Poland. In 1932, mathematician Marian Rejewski used intercepted code books and pure mathematics to reconstruct the machine's internal wiring — a feat the Germans considered impossible. His colleagues Jerzy Różycki and Henryk Zygalski built mechanical devices called "bomby" that could test Enigma settings automatically. When Germany increased security in 1938, the Poles shared everything with Britain and France weeks before the invasion.
At Bletchley Park, Alan Turing redesigned the bombes into faster electromechanical devices that could test thousands of rotor positions per hour. His crucial insight was the "crib" method: matching known plaintext fragments (weather reports always began the same way) against ciphertext to eliminate impossible settings. By 1943, Bletchley was reading most German military traffic within hours, feeding intelligence — codenamed Ultra — to Allied commanders across every theatre of war.
Historians estimate that Ultra shortened the war by at least two years and saved millions of lives. Yet the secret was kept until 1974, and the Polish contribution was suppressed even longer. Turing, prosecuted for homosexuality in 1952, was chemically castrated and died in 1954. He received a royal pardon in 2013 — fifty-nine years too late for the man who broke the unbreakable.
