I didn't know this - from wikipedia page on Enigma[1]:

> Despite the seeming difficulty in decrypting its messages, Enigma contained a number of design issues that left patterns in the cyphertext. Poland first cracked the machine as early as December 1932 and was able to read messages prior to and into the war. Poland's sharing of their achievements enabled the Allies to exploit Enigma-enciphered messages as a major source of intelligence.

Ok interesting, so why do people talk about Turing in this connection then?

> Turing devised techniques for speeding the breaking of German ciphers, including improvements to the pre-war Polish bomba method, an electromechanical machine that could find settings for the Enigma machine

Ok so Turing just improved an existing method. Without being an actual expert it's impossible to know how much credit he actually deserves.

Two more references: the Polish method was called "Bomba" [3] invented by Marian Rejewski [4]

[1] https://en.wikipedia.org/wiki/Enigma_machine

[2] https://en.wikipedia.org/wiki/Alan_Turing

[3] https://en.wikipedia.org/wiki/Bomba_(cryptography)

[4] https://en.wikipedia.org/wiki/Marian_Rejewski