Polish Cipher Bureau

The interwar Polish codebreakers who first broke Enigma

Overview

The Cipher Bureau of the Polish General Staff recruited mathematicians from Poznan University, and in December 1932 Marian Rejewski reconstructed the wiring of the German military Enigma machine using permutation theory and documents supplied by French intelligence. With Jerzy Rozycki and Henryk Zygalski he developed the cyclometer, perforated Zygalski sheets and the electromechanical bomba to recover daily keys. In July 1939, weeks before the German invasion, the Poles handed replica machines and their methods to British and French codebreakers at Pyry near Warsaw, laying the foundations of the Ultra effort at Bletchley Park.