Henryk Zygalski 1908-1978

1908  Born on 15 July in Posen, then part of the German Empire, now Poznań.

1918  Poland gains independence from Germany.

1923  Arthur Scherbius launches prototype Enigma machine.

1926  Undergraduate at Poznań University. Poland starts intercepting German Enigma messages.

1928  Marian Rejewski, Jerzy Różycki and Henryk Zygalski selected for code-breaking course: all were also fluent in German.

1931  Graduates with MPhil and all three work for Polish Cipher Bureau.

1932  Marian Rejewski reverse-engineers the Enigma machine, the first step towards decrypting Enigma messages.

1938  Invents Zygalski sheets to detect Enigma machine settings.

1939  July: Polish cryptanalysts meet with British and French allies at Pyry near Warsaw to share information and expertise.

1939  September: As the German army approaches Poland, the three cryptanalysts leave for France, via Romania and Italy.

1939  October: take up deciphering Enigma near Paris.

1940  Turing meets with Rejewski, Różycki and Zygalski in Paris. After France is invaded, the Poles fly to North Africa to get false identities.

1942  The Polish cryptanalysts return to Uzès, in Vichy France but Różycki is drowned en route. German army occupies southern France.

1943  Rejewski and Zygalski escape to Spain; on the way they are robbed and imprisoned but released. They cross to Portugal to board a British naval vessel, HMS Scottish, in Lisbon for Gibraltar. They fly to the UK and join the Polish Signals Battalion at Boxmoor, near Hemel Hempstead.

1945  World War II ends in Europe.

1947  Polish University College established in Knightsbridge and Putney. Zygalski is appointed to teach mathematics.

1949  Described by his tutor as “quite a good mathematician “. Becomes a British citizen.

1950  Zygalski is awarded London University MSc.

1951  Battersea Polytechnic takes over Putney Buildings.

1954  Death of Alan Turing.

1966  Battersea Polytechnic becomes the University of Surrey and moves to Guildford.

1968  Zygalski suffers a stroke and retires. His speech is impaired.

1973  Evidence begins to emerge in Poland of involvement in code-breaking of Rejewski, Różycki and Zygalski.

1974  Role of Bletchley Park becomes known for the first time.

1977  Awarded DSc Honoris Causa by the Polish University Abroad.

1978  Dies in Liss, Hampshire on 30 August and is cremated in Chichester.

2000  With Rejewski and Różycki, awarded Grand Cross of the Order of Polonia Restituta

2002  Memorial to Rejewski, Różycki and Zygalski unveiled at Bletchley Park.

2007  Monument to Rejewski, Różycki and Zygalski unveiled in Poznań Castle.

2014  Rejewski, Różycki and Zygalski given Milestone Award by Institute of Electrical and Electronics Engineers.

2018  Memorial stone to Zygalski unveiled in Chichester Crematorium by the Polish Ambassador and Dr Jeremy Russell (Zygalski’s nephew).

2026  Launch of Polish Navy signal intelligence ship ORP Henryk Zygalski.

2026  Zygalski recognised at the University of Surrey.

The Polish Cipher Bureau was part of the Polish Army and a development of Polish cryptography from World War I.

In 1929 a mysterious package arrived for a German firm in Warsaw, with a declaration that it was radio equipment. The firm pressed for the package to be returned straight-away to Germany, saying that it had been sent by mistake, but the Polish authorities took advantage of a weekend to open the package, see that it was a cipher machine, examine it closely and put it back.

This proved to be a ‘commercial’ model of the Enigma machine. More forbidding was the military model, which had additional security features, including secret wiring. The number one challenge for the Cipher Bureau was to understand its operation and then to devise techniques to discover the protocol used by the Germans to set the adjustable components of the machine (rotor order, starting position, cross-pluggings, &c.) when they sent messages.

Fortunately the Cipher Bureau had a boost when an officer from French Military Intelligence shared a couple of documents acquired from a German spy. These were the operating instructions and set-up guide, with photographs, for the military model Enigma machine. There were, however, no wiring diagrams.

Setting to work with these documents, a sheaf of intercepts, and a ‘commercial model’ Enigma machine bought by the Cipher Bureau in 1926, Marian Rejewski – one of three mathematicians recruited by the Cipher Bureau, the others being Henryk Zygalski and Jerzy Różycki – began to use his expertise in Group Theory to create permutation equations modelling the behaviour of the military Enigma machine. Painstakingly and with some inspired guesswork he was able to reverse-engineer the machine.

That work enabled the Cipher Bureau to construct replica Enigma machines and to find out how the adjustable components were set. The adjustments were made regularly – by the time of the outbreak of World War II, daily – creating a new puzzle with every change. In this task, all three Polish mathematicians made significant breakthroughs. One was the development of Zygalski sheets for detecting how the Enigma machine had been set up that day: this enabled Enigma messages to be decrypted for the crucial opening months of the war.

In July 1939, only weeks before the outbreak of the war, Poland gave the Allies all its knowhow on Enigma, transforming overnight the Allies’ ability to master Enigma. Broken Enigma messages formed the core of Allied military intelligence against Germany. The war may have had a very different trajectory without that critical Polish contribution.

The Polish University Abroad, or the Polish University in Exile, was established in London in 1949.

J J O’Connor and E F Robertson (St Andrews University*) write:

During the war a Polish Government-in-Exile operated in Britain and in 1942 it set up a Commission for Higher Technical Education. The object of the Commission was to train scientists and engineers who would be in a position to lead reconstruction in Poland after the war ended. However, after the war ended, Poland became part of the Soviet system and, although Poles could return to their home country from Britain, nevertheless, they knew that the Communist government would treat them with considerable suspicion.

Although some returned, as for example Rejewski did, nevertheless the majority, including Zygalski, decided to remain in Britain. The original purpose of the Commission for Higher Technical Education having gone, it became, by Act of Parliament, the Polish University College in 1947.

The College, based in eight buildings between Knightsbridge and Putney, taught courses with the aim that students would sit examinations for external University of London degrees. A student was taught in Polish for two years and then courses would be in English. Some features of a Polish education were retained, such as students writing a thesis in their final year, but the curricula were essentially those of the University of London.

Zygalski was appointed to teach at the Polish University College from the time it was set up.

The Polish University College was amalgamated with Battersea Polytechnic Institute in 1951. Battersea Polytechnic Institute became the University of Surrey in 1966. The Polish University Abroad continues to operate in France and Germany.

*reproduced with permission.

Henryk Zygalski’s most famous contribution to Enigma codebreaking was the Zygalski sheets. These were large, square, perforated cardboard sheets which enabled the codebreakers to find how the Enigma machine had been set up for encryption.

Before the war, when Zygalski started work on the problem, the German military Enigma machine used three interchangeable rotors which could be inserted into any of the three slots in the machine. Then the rotors would be turned to a chosen starting-position, with one of the 26 letters engraved on the rim of each rotor facing uppermost. There were 6 possible ways to insert the rotors and 17,576 possibilities for the rotor orientation.

German signalling protocol required the message sender to notify the starting-position to the recipient at the beginning of the signal. It would be foolish for this information to be sent without disguising it, so the Enigma machine itself was used to encipher the starting-position. The operator would choose three random letters, set the machine up with those three letters uppermost, and type in the three actual starting-position letters to get an enciphered version. Then the two sets of three letters – the first three random letters, and the enciphered version of the starting-position would be sent to the recipient. This ought to have been secure, if the enemy did not know the rotor order, cross-plugging, or other variables in use on that day.

Zygalski exploited a flaw in the protocol which was that the starting-position was being sent twice over. Codebreaking theory holds that repetition of a piece of clear text in the same cipher system can be exploited to break the cipher. Here the repetition was tiny – three letters only – but that was enough.

Zygalski’s method was to look for repetitions in the enciphered double triplet appearing at the start of intercepted messages. If the sender had chosen, say, ABC as the actual starting-position, this might come out as WFTYFG in the double triplet: here, with F as the middle letter. Other double-triplets might have repetitions in the first and fourth, or third and sixth positions. These repetitions can only arise with certain rotor orders and a limited number of starting-positions.

An exhaustive tabulation of all possible rotor orders and all possible starting-positions was made. The results were punched out onto the large cardboard sheets which are now known by Zygalski’s name. Each sheet would be ruled into squares for all 26 possible positions of the right-hand rotor (vertical axis) and all 26 positions of the middle rotor (horizontal axis). Holes were punched in squares where the three rotors could allow for a repeat in the double triplet. A separate sheet was made for each of the 26 positions of the left-hand rotor.

The basic principle in using Zygalski sheets was to stack them on top of each other on a light-table, one sheet for each signal with a repeat in the double triplet. The sheets would be offset to reflect the difference of initial set-up between the signals. Then the codebreaker’s task was to find a set of sheets – modelling a rotor order and start position – for which the holes lined up and the light shone through.

During the course of the war, Germany produced Enigma machines with more rotors, so were much more secure. This would have increased the number of necessary Zygalski sheets, making the procedure unusable. That was why Bletchley Park had to develop the Bombe machine, an electro-mechanical device for testing possible rotor settings, developed from an earlier Polish design.

There is a Science Museum article on Zygalski sheets here.

The stories of Henryk Zygalski and Alan Turing overlap in that they were both mathematicians who found their way into the problem of breaking the Enigma cipher, and both had associations with Guildford. Henryk Zygalski’s work on the Enigma problem began around 1933, shortly after Marian Rejewski solved the wiring of the Enigma machine; Alan Turing’s six years later, in early 1939, when he was put on the ‘Emergency List’ of standby recruits to British codebreaking in preparation for an expected war. Zygalski’s work on the system ended in 1942 when the German army seized the south of France, forcing him to seek an escape. Alan Turing’s ended at around the same time, when he was redeployed onto the problem of secure encipherment of voice calls.

Alan Turing was not part of the British team that went to Warsaw in July 1939, and came back with the astonishing gift of everything the Polish cryptanalysts knew about Enigma. When the war broke out, he was brought to Bletchley Park, whereas the Poles had to escape from Poland as their country was overrun in September 1939. They ended up in France, stationed with the codebreakers of French Military Intelligence, until in turn France was invaded and they had to escape again to North Africa.

In the short period when Henryk Zygalski was based near Paris, in early 1940, the British were busy creating a replica set of Zygalski sheets for their own use. They also promised to send a set across to France. And they were puzzled: using the sheets wasn’t easy, and the British codebreakers struggled to make Zygalski’s system work.

The answer was a conference: a senior British Enigma expert should go to France and consult with the Polish experts, taking the sheets with him. The envoy chosen for the mission was Alan Turing.

So, in early 1940, there took place the only known encounter between Alan Turing and Henryk Zygalski. Marian Rejewski said that “We treated [Turing] as a younger colleague who had specialised in mathematical logic and was just starting out in cryptology”. Given the imbalance of experience, that sounds like a fair assessment. The Poles and their French hosts took Turing to dinner; the historian Władysław Kozaczuk picks up the story.

‘The attention of the diners was drawn to a crystal flower glass with flowers, placed on the middle of the tablecloth. They were delicate rosy-lilac flowers with slender funnel-shaped calyces… Turing… gazed in silence at the flowers and the dry lanceolate leaves. He was brought back from his reverie, however, by the Latin name, Colchicum autumnale (autumn crocus, or meadow saffron), spoken by the mathematician-geographer Jerzy Różycki. “Why, that’s a powerful poison!” said Turing in a raised voice.”

The Poles explained how to use the Zygalski sheets best and solved the puzzle which had been confusing the British at Bletchley. In his turn, Turing was able to explain something which had puzzled the Poles, namely the peculiar measurements of the British version of the Zygalski sheets, whose holes were 8.5 mm square. ‘That’s perfectly obvious,’ he explained, ‘It’s simply one-third of an inch.’

The other connection between Turing and Zygalski is Guildford, but that is a more tenuous link. Turing never lived there, though his parents’ retirement home and his brother’s family home were both in the town and he was a frequent, if irregular, visitor. Zygalski’s teaching career in the University of Surrey began after Turing’s death.

Many people have helped in preparing the text for this webpage, including Henryk Zygalski’s nephew and nieces – Dr Jeremy Russell, Georgina Donaldson and Anna Zygalska-Cannon. Special thanks are due to Sir Dermot Turing who did a large part of the drafting, Professor David Uzzell and Professor Robert Gawłowski.

All photographs are © Anna Zygalska-Cannon. No part of this webpage may be reproduced without permission.

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Gawłowski, R (2023) The First Enigma Codebreaker. Pen and Sword Military, Barnsley, UK. ISBN 978-1-3990-6910-6   This is a biography of Marian Rejewski who passed the baton to Alan Turing.

Turing, D (2018) X Y & Z: The real story of how Enigma was broken. The History Press, Brimscombe Port, UK. ISBN 978-0-7509-8782-0

Turing, D (2023) Enigma traitors: The Struggle to Lose the Cipher War. The History Press, Brimscombe Port, UK. ISBN 978-1-8039-9169-6    The story of how excellence in codebreaking was nearly betrayed by incompetence in codemaking.

Turing, D (2025) Misread signals: How History Overlooked Women Codebreakers. History Press, Brimscombe Port, UK. ISBN: 978-1-8039-9793-3

Kapera, Z.J (2015) The Triumph of Zygalski’s Sheets. The Enigma Press, Mogilany, Poland and M&M Baldwin, Cleobury Mortimer, UK. ISBN 978-83-86110-79-7