Helping Turing: How Three Polish Mathematicians Cracked the Enigma Code

Barbara Jeffery

4 mins

14 Aug 2019

Alan Turing, genius of Enigma code-breaking during World War Two, will be the face on Britain’s next £50 note, which we’ll see in 2021.  The three young Polish mathematicians who were the first to crack the new German military Enigma code got their faces on a modest 5 zloty postage stamp in 1983.

Revealing the secret

Less than six weeks before World War Two began, on 3 September 1939, Lieutenant Gwido Langer, head of the Polish Central Staff’s cipher bureau invited British and French intelligence chiefs to a meeting at his secret cryptology centre at Pyry in the Kabaty woods near Warsaw.

There he revealed to them that his team had cracked the Enigma code seven years before and had been reading German messages ever since. This was five years before Alan Turing had even started studying cryptology – while working on a degree in mathematical logic at Princeton University in the United States (Princeton was famous for attracting the brightest and best young mathematicians in the 1930s).

It’s not clear why the Poles had kept this secret, but it was the certainly the fact that war was about to break out that made them share it.

It was the work of those three Polish students, Marian Rejewski, Henryk Zygalski and Jerzy Rozycki, that set Alan Turing on the way to breaking the German codes when he arrived at the Government Code and Cypher School at Bletchley Park on 4 September 1939, the day after war broke out.

Join Dan Snow on an exclusive tour of the house and grounds, as well as the little known but all-important cottages that surround Bletchley Park.Watch Now

The inside man

In November 1931 Hans Thilo Schmidt, a hard-up womaniser in the German cipher department, sold the French intelligence service the users’ manual and code books of the Enigma machine the German army had been using since June 1930.

Captain Gustave Bertrand, the thirty-four year old head of the Deuxieme Bureau’s code section was intrigued; in spite of all his efforts, he hadn’t received any information about the new machine.

But the French army’s cipher section – reputedly one of the best in the world –  was not impressed by Hans Thilo Schmidt’s information: the manual explained how to put messages into code but did not explain how to read an encrypted message. British code experts agreed it would not help them to break the code.

Bertrand was disappointed but he was given permission to show the precious papers to Lieutenant Gwido Langer. He saw this information was important but it was not enough and he asked for more.

Nine days later Schmidt gave Gustave Bertrand a list of the current settings in use, which he passed on to the Poles. Still they got nowhere.

Gustave Bertrand.

The Poles attempt to break the code

Back in January 1929 the Poles had set up a cryptology course at Poznan university. It was a tough course using, for the first time, pure mathematics, rather than language.

The three brightest students, Rejewski, Zygalski and Rozycki, who was only nineteen, were invited to work at the Polish army cipher bureau part-time while continuing their studies. Rejewski graduated in March 1929 at the age of twenty-three and went on working for the bureau as well as teaching maths at the university.

In October or November Rejewski was asked to do some extra work secretly; he was not to tell his two friends. After a few weeks of intensive study he was able to work out the electrical wiring inside the German machine and had a machine of his own made. It was the size of a portable typewriter.

Zygalski and Rozycki were called in to help and by the end of the year they could read German messages. Rejewski had built his own Enigma machine.

It’s not clear why the Poles kept this secret for so long but it was the prospect of approaching war that finally made them hand it over, and the fact that Britain and France had promised to support Poland if Hitler invaded.

Dan sat down with Roger Moorhouse to talk about the start of World War Two from the often-overlooked Polish perspective, sorting the fact from the fiction about Germany's infamous invasion.Watch Now

Why do we hear little about these three code-breakers?

The secrecy demanded of everyone who worked at Bletchley (and the same from the Communist Party that took over Poland and did not want any links with the west publicised) meant that the three students’ work was almost forgotten. But not quite.

After the postage stamp, a three-sided bronze monument was erected in front of the castle in Poznan, a name of one of the men on each side.

2007 monument to cryptologists Rejewski, Różycki, and Zygalski in front of Poznań Castle. Image credit: Pnapora / Commons.

There is also a board at Bletchley Park that reads, in English and Polish:

“This plaque commemorates the work of Marian Rejewski, Jerzy Rozycki and Henryk Zygalski – mathematicians of the Polish intelligence service – in first breaking the Enigma code. Their work greatly assisted the Bletchley part code-breakers and contributed to the Allied victory in World War Two.”

Sir Harry Hinsley, who worked at Bletchley Park and co-authored British Intelligence in the Second World War said the Poles’ work was “invaluable,” and other experts say it shortened World War Two by two years.

“The Turing cult has obscured the role of the Polish code-breakers,”

acknowledged Alan Turing’s nephew, Sir Dermont Turing,  author of Prof  a biography of his uncle, and Z,Y and Z, the real story of how Enigma was broken.

Barbara Jeffery has spent several years unearthing the shocking and sometimes hilarious hidden story of Monty Newton and Rodolphe Lemoine. “Chancers: Scandal, Blackmail and the Enigma Code” will be published on 15 August, by Amberley Publishing.

Featured Image: 2005 Bydgoszcz memorial unveiled on the centennial of Rejewski’s birth. It resembles the Alan Turing Memorial in Manchester. Wojsyl / Commons.