How did Marian Rejewski crack the German Enigma machine?

Marian Rejewski was a brilliant Polish mathematician and cryptologist who successfully reconstructed the sight-unseen German military Enigma cipher machine in late 1932. Working at the Polish Cipher Bureau alongside Jerzy Różycki and Henryk Zygalski, he invented groundbreaking tools like the cyclometer and the cryptologic bomb to read encrypted messages. Just weeks before World War II, Poland shared these vital methods with British and French intelligence, laying the groundwork for the Allied Ultra intelligence effort.

What we know

• Marian Rejewski reconstructed the German military Enigma cipher machine sight-unseen in late 1932. [2]
• Rejewski developed the cryptologic card catalog and the cryptologic bomb to help decrypt Enigma messages. [2, 3]
• Five weeks before World War II began, the Polish Cipher Bureau shared its Enigma-decryption techniques and equipment with French and British intelligence. [4]
• After the war, Rejewski remained silent about his prewar and wartime cryptologic work for two decades to avoid scrutiny from Poland's Soviet-dominated government. [2]

Where to go next

• how it workedWhat was the cryptologic bomb designed by Rejewski?
• how we knowHow did the cyclometer help decrypt Enigma ciphertext?
• the bigger pictureWhat role did the Cipher Bureau play in Polish intelligence?
• what followedHow did British codebreakers at Bletchley Park use Polish breakthroughs?
• whoWho were Rejewski's fellow mathematicians at the Cipher Bureau?
• an unexpected connectionHow were university engineering drawings used to rebuild historical codebreaking gear?Using historical drawings made by Rejewski, engineering staff at the University of Cambridge constructed a working version of his cyclometer decades later in 2019.

Sources

• [1]Marian Rejewski (Wikidata Q160411) · CC0 1.0
• [2]Marian Rejewski · CC BY-SA 4.0
• [3]Bomba (cryptography) · CC BY-SA 4.0
• [4]Cipher Bureau (Poland) · CC BY-SA 4.0
• [5]Cyclometer · CC BY-SA 4.0