Marian Rejewski

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Marian Adam Rejewski (16 August 1905 – 13 February 1980) was a Polish mathematician and cryptologist who in late 1932 reconstructed the sight-unseen Nazi German military Enigma cipher machine, aided by limited documents obtained by French military intelligence.

Over the next nearly seven years, Rejewski and fellow mathematician-cryptologists Jerzy Różycki and Henryk Zygalski developed and used techniques and equipment to decrypt the German machine ciphers, even as the Germans introduced modifications to their equipment and encryption procedures.

Five weeks before the outbreak of World War II in Europe, the Poles shared their technological achievements with the French and British at a conference in Warsaw, thus enabling Britain to begin reading German Enigma-encrypted messages, seven years after Rejewski's original reconstruction of the machine.

The intelligence that was gained by the British from Enigma decrypts formed part of what was code-named Ultra and contributed—perhaps decisively—to the defeat of Nazi Germany.

Marian Rejewski was born 16 August 1905 in Bromberg in the Prussian Province of Posen (now Bydgoszcz, Poland) to Józef and Matylda, née Thoms.

After completing secondary school, he studied mathematics at Poznań University's Mathematics Institute, housed in Poznań Castle.

In 1929, while studying mathematics at Poznań University, Rejewski attended a secret cryptology course conducted by the Polish General Staff's Cipher Bureau (Biuro Szyfrów), which he joined in September 1932.

In 1929, shortly before graduating from university, Rejewski began attending a secret cryptology course which opened on 15 January, organized for select German-speaking mathematics students by the Polish General Staff's Cipher Bureau with the help of the Mathematics Institute's Professor Zdzisław Krygowski.

On 1 March 1929 Rejewski graduated with a Master of Philosophy degree in mathematics.

A few weeks after graduating, and without having completed the Cipher Bureau's cryptology course, he began the first year of a two-year actuarial statistics course at Göttingen, Germany.

He did not complete the statistics course, because while home for the summer of 1930, he accepted an offer, from Professor Krygowski, of a mathematics teaching assistantship at Poznań University.

He also began working part-time for the Cipher Bureau, which by then had set up an outpost at Poznań to decrypt intercepted German radio messages.

Rejewski worked some twelve hours a week near the Mathematics Institute in an underground vault referred to puckishly as the "Black Chamber".

The Bureau had had no success in reading Enigma-enciphered messages and set Rejewski to work on the problem in late 1932; he deduced the machine's secret internal wiring after only a few weeks.

Rejewski and his two colleagues then developed successive techniques for the regular decryption of Enigma messages.

His own contributions included the cryptologic card catalog, derived using the cyclometer that he had invented, and the cryptologic bomb.

The Poznań branch of the Cipher Bureau was disbanded in the summer of 1932.

In Warsaw, on 1 September 1932, Rejewski, Zygalski, and Różycki joined the Cipher Bureau as civilian employees working at the General Staff building (the Saxon Palace).

Their first assignment was to solve a four-letter code used by the Kriegsmarine (German Navy).

Progress was initially slow, but sped up after a test exchange—consisting of a six-group signal, followed by a four-group response—was intercepted.

The cryptologists guessed correctly that the first signal was the question, "When was Frederick The Great born?"

On 20 June 1934 Rejewski married Irena Maria Lewandowska, daughter of a prosperous dentist.

The couple eventually had two children: a son, Andrzej (Andrew), born in 1936; and a daughter, Janina (Joan), born in 1939.

Janina would later become a mathematician like her father.

The Enigma machine was an electromechanical device, equipped with a 26-letter keyboard and 26 lamps, corresponding to the letters of the alphabet.

Inside was a set of wired drums (rotors and a reflector) that scrambled the input.

The machine used a plugboard to swap pairs of letters, and the encipherment varied from one key press to the next.

For two operators to communicate, both Enigma machines had to be set up in the same way.

The large number of possibilities for setting the rotors and the plugboard combined to form an astronomical number of configurations, and the settings were changed daily, so the machine code had to be "broken" anew each day.

Five weeks before the Nazi German invasion of Poland in 1939, Rejewski and colleagues presented their achievements to French and British intelligence representatives summoned to Warsaw.

Shortly after the outbreak of war, the Polish cryptologists were evacuated to France, where they continued breaking Enigma-enciphered messages.

The course was conducted off-campus at a military facility and, as Rejewski would discover in France in 1939, "was entirely and literally based" on a 1925 book by French colonel Marcel Givierge, Cours de cryptographie (Cryptography Course).

Rejewski and fellow students Henryk Zygalski and Jerzy Różycki were among the few who could keep up with the course while balancing the demands of their normal studies.

They and their support staff were again compelled to evacuate after the fall of France in June 1940, and they resumed work undercover a few months later in Vichy France.

After the French "Free Zone" was occupied by Nazi Germany in November 1942, Rejewski and Zygalski fled via Spain, Portugal, and Gibraltar to Britain.

There they enlisted in the Polish Armed Forces and were put to work solving low-grade German ciphers.

In the aftermath of World War II, Rejewski reunited with his family in Poland and worked as an accountant.

For two decades, he remained silent about his prewar and wartime cryptologic work to avoid adverse attention from the country's Soviet-dominated government; he broke his silence in 1967 when he provided to the Polish Military Historical Institute his memoirs of his work in the Cipher Bureau.

He died at age 74 of a heart attack and was interred with military honors at Warsaw's Powązki Military Cemetery.