Polish mathematicians break Enigma

Marian Rejewski and colleagues at Poland's Cipher Bureau worked out how the German Enigma machine functioned, and built tools to read its messages. They shared their methods with Britain and France in 1939.

Context

Rejewski began work on the German military Enigma in 1932, after the Polish Cipher Bureau recruited mathematics graduates from Poznan. Earlier attempts had treated the problem as a language puzzle. He treated it as a problem in permutation theory, and the breakthrough is usually placed in late 1932. He was helped by two fellow mathematicians, Jerzy Rozycki and Henryk Zygalski, and by documents obtained through French intelligence.

Poland then turned theory into routine reading. The team reconstructed the machine's wiring, produced duplicate machines, and built aids to recover the daily settings, including a device called the bomba. German changes to procedure and extra rotors in the late 1930s made the work far more costly.

With a German invasion looming, Poland disclosed its methods at a secret meeting in Warsaw on 24 to 26 July 1939. Britain and France each received a replica Enigma and technical drawings. That gave Bletchley Park a head start, and Alan Turing and others later extended the method with a far larger machine. Historians debate how much the British owed to the Poles, but the Polish break is widely accepted as the first.