Marian Rejewski

Poland's Biuro Szyfrów did something no other intelligence service did in the 1920s: it hired mathematicians instead of linguists. Rejewski was 27 when Enigma landed on his desk. The attack rested on permutation group theory — the Germans sent the message key twice at the start of every message, and that repetition produced equations relating the rotor permutations to each other. By December 1932 he had the rotor wiring and the entry drum, helped along by documents French intelligence had bought from a German official.

With Jerzy Różycki and Henryk Zygalski he then industrialised the method: the cyclometer and its card catalogue, Zygalski's perforated sheets, and in 1938 the bomba kryptologiczna, six linked Enigma replicas grinding through rotor positions mechanically. When the Germans added two more rotors in December 1938 the workload went up tenfold, and Poland ran out of money well before it ran out of ideas.

On 25 July 1939, at Pyry outside Warsaw, the Poles handed the lot to the British and French, replica machines included. Rejewski spent the war in France and then Britain working on lower-grade ciphers, never told what Bletchley was doing, and after 1946 worked as an office clerk in Bydgoszcz. His part in it only became publicly known in the 1970s.