Marian Rejewski, a mathematician at the University of Poznań, together with Jerzy Różycki and Henryk Zygalski, breaks the German Wehrmacht's Enigma code in 1932 using algebraic group-theory techniques, without access to the physical hardware. In July 1939, weeks before the German invasion of Poland, the Poles share their methods and a replica Enigma with British and French intelligence services. Bletchley Park, where Alan Turing and Gordon Welchman developed the Bombe, was built on Polish mathematical foundations. The Anglophone narrative has historically attributed the breaking of Enigma almost exclusively to Turing; the Polish cryptographers, who achieved it seven years earlier, remain unknown outside Poland.