Which German cipher machine did Alan Turing help break?

The German cipher machine Alan Turing helped break was Enigma. Used by Nazi Germany to encrypt military communications, Enigma employed rotating wheels, or rotors, along with plugboard connections to create an enormous number of possible settings.

At Bletchley Park, Turing developed methods for attacking Enigma and designed the British bombe, an electromechanical device that searched for settings consistent with likely plaintext. The machine did not simply read messages automatically; human cryptanalysts first identified probable phrases, called cribs, which guided the bombe's tests.

Turing's work was especially important against German naval Enigma, whose messages helped coordinate U-boats in the Atlantic. The Polish Cipher Bureau had already made crucial breakthroughs before the war, and British codebreakers built on that foundation. Typex was a British machine, Purple was Japanese, and Lorenz was a separate German teleprinter cipher system.