Poles smuggled out a complete first-model Enigma machine, performed the cryptanalysis that revealed its core weakness, and also created the first of the "bombe" machines used for most of the decryptions.

Bletchley Park acted as central clearinghouse for intercepted ciphertexts, distributing decryptions with elaborate care to keep the Germans from knowing Enigma had been cracked. Late in the war, they built an electronic gadget called Colossus to decrypt traffic from a much more difficult version of Enigma.