Long before Alan Turing and the codebreakers of Bletchley Park became synonymous with the defeat of the German Enigma cipher, three Polish mathematicians had already solved the machine's underlying mathematics — using pencil, paper, and group theory rather than captured hardware or brute force. Marian Rejewski, Jerzy Różycki, and Henryk Zygalski broke Enigma's wiring in the winter of 1932 and 1933, years before the war that would make their work indispensable, and their achievement, handed to French and British intelligence six weeks before Germany invaded their own country, became the seed from which Bletchley Park's later success grew.
Recruits from a University Mathematics Course
Poland's Cipher Bureau, the Biuro Szyfrów, had watched the growing sophistication of German military communications with alarm through the 1920s. In 1932, seeking fresh minds rather than career cryptographers, the bureau recruited a small group of mathematics students from the University of Poznań, a region chosen partly because many of its graduates had grown up bilingual in German and Polish. Among them were Rejewski, Różycki, and Zygalski, all in their twenties, who were given a working knowledge of a commercial Enigma machine and set the seemingly impossible task of reconstructing the wiring inside the far more complex military version, which no Polish cryptographer had ever seen opened.
The bureau's task was aided by a piece of human intelligence. French military intelligence, through an officer named Gustave Bertrand, had obtained operating manuals and monthly key settings for the military Enigma from a German Cipher Office employee, Hans-Thilo Schmidt, who sold the documents to French intelligence for money. The material did not reveal the internal wiring of the machine's rotors, but it gave Rejewski enough operational detail to attempt a mathematical reconstruction.
Solving Enigma Without a Machine
Working largely alone, Rejewski applied permutation group theory to the problem, treating the relationships between plaintext and ciphertext letters as mathematical equations rather than a linguistic puzzle. By December 1932, using the key material Bertrand had supplied and his own mathematical deductions, Rejewski had worked out the wiring of the machine's rotors and reflector — a feat later cryptologic historians have called one of the most important breakthroughs of twentieth-century mathematics, achieved without ever having examined the inside of a military Enigma machine.
With the wiring known, the Polish team built working replicas of the German machine and, through the mid-1930s, developed a series of techniques to recover the daily key settings the Germans changed constantly. Różycki devised the "clock method," which helped identify which rotor the Germans had placed in the machine's rightmost position on a given day. Zygalski designed a system of perforated paper sheets — later known as Zygalski sheets — that let cryptographers narrow down key settings by overlaying sheets representing different rotor orders and looking for points where holes aligned across all of them. In 1938, Rejewski designed an electromechanical device called the "bomba kryptologiczna," or cryptologic bomb, which mechanized the search for daily keys and directly inspired the design principle behind the much larger bombe machines Turing's team would later build at Bletchley Park.
A Deteriorating Position
By the late 1930s, the German military was steadily increasing Enigma's complexity, adding additional interchangeable rotors and expanding the number of plugboard connections, which multiplied the number of possible settings far beyond what Poland's modest resources could keep pace with. The bureau's leadership recognized that Poland, facing an increasingly aggressive Germany and lacking the industrial capacity to mechanize codebreaking at scale, could not sustain the effort alone much longer. With war looking increasingly likely, Polish intelligence made the consequential decision to share its work rather than guard it.
The Meeting at Pyry and the Handover
In late July 1939, five weeks before the German invasion, Polish intelligence hosted a secret meeting with representatives of French and British intelligence at a facility in the Kabaty Woods near the village of Pyry, south of Warsaw. There, Rejewski and his colleagues revealed the full extent of their achievement to their astonished allies, who had made comparatively little progress against Enigma on their own. The Poles handed over reconstructed Enigma machines, complete technical documentation of their wiring solution, and copies of the Zygalski sheets and other techniques they had developed over nearly seven years of work.
Germany invaded Poland on September 1, 1939. Rejewski, Różycki, and Zygalski escaped through Romania and eventually reached France, where they continued codebreaking work for French intelligence until France's own collapse in 1940 forced them into hiding and, for some, into further flight. Różycki drowned in 1942 when a ship carrying him between French colonial postings sank in the Mediterranean; Rejewski and Zygalski eventually reached Britain but were never invited to work at Bletchley Park itself, a decision historians attribute to strict wartime compartmentalization rather than any doubt about their ability.
The Foundation Beneath Bletchley Park
The material handed over at Pyry gave British cryptographers, including Turing, a working head start they had lacked entirely on their own, letting them move directly into extending Polish methods against Enigma's growing complexity rather than starting from first principles. The much larger and more famous Bletchley Park bombes that decrypted German military traffic throughout the war built conceptually on Rejewski's original bomba. For decades after the war, the Polish contribution remained obscure, overshadowed by the scale and secrecy of the British effort, until historical accounts in the 1970s and beyond restored proper credit to the three mathematicians whose work, born in a modest Warsaw office years before the war began, quietly shaped one of the Allies' most consequential intelligence advantages.
