David Forfar discusses the role of Polish cryptologists – including a would-be actuary – in cracking Enigma during the Second World War
The 8th of May marked the 75th anniversary of the guns falling silent in Europe. This year, the wartime cryptography centre Bletchley Park had been due to hold an exhibition celebrating wartime cryptography – but COVID-19 intervened. It is not well known, at least not in the UK, that the first cryptologist to break the German military ‘Enigma’ coding machine of the Second World War was not Alan Turing, nor any British or French cryptologist, but Marian Rejewski of the Polish Cipher Bureau. He accomplished this in 1932, seven years before Alan Turing started to work at Bletchley Park. It was an astonishing feat of cryptographic virtuosity, as the best British and French cryptologists had been unable to break Enigma. The German cryptologists considered Enigma to be unbreakable.
That Rejewski possessed one of the finest cryptological minds of his generation was confirmed by the eminent US cryptologist David Kahn, who described Rejewski’s achievements as “one of the finest in the history of the art”.
The road not taken
Many British actuaries are probably unaware that when Rejewski graduated from university he had intended to pursue an actuarial career with Polish insurance company Westa. With this in mind, he had attended a postgraduate course in actuarial mathematics at Göttingen University in 1929. However, as war loomed closer, Rejewski gave up the chance of a promising actuarial career and patriotically volunteered to join the Polish Cipher Bureau.
While the Polish had succeeded in manufacturing an exact working replica of Enigma, there were 1,270,430,011,730,880,000 possible ways for an operator to set it up – even on the most basic machine. Despite this, the Polish had been able to determine which particular setting the sender had used to encrypt the message – a superb achievement!
The Polish cryptologists realised that if Poland were to be invaded, they would have to flee the country. Furthermore, they knew that, because of regular German improvements, Poland could not afford to manufacture indefinitely the number of mechanical machines that were necessary for continuing to decrypt Enigma. However, the UK and the USA, given the will, could.
“The Polish had worked out the military Enigma’s complicated internal wiring using mathematical theory – not, as later believed, by the capture of an actual Enigma machine”
Sharing the secret
In view of these considerations and the likely invasion, Poland’s senior military obtained clearance to reveal to
the chief British cryptologists, Alistair Denison and Dillwyn (Dilly) Knox (and their French counterparts), the highly-classified secret that the Polish Cipher Bureau had been ‘cracking’ Enigma on an almost daily basis since 1932. Thus, in 1939, on the eve of invasion, the Polish cryptologists informed their British and French counterparts that they needed to come to Pyry, near Warsaw, to hear something important.
At the meeting, the Polish explained that they had worked out Enigma’s complicated internal wiring using mathematical theory (not, as later believed, by the capture of an actual Enigma machine), and that they would supply the British and French with a working replica model. Knox was rather taken aback when he heard that, for the past seven years, the Polish had been accomplishing the very thing that the British codebreakers had been trying to achieve.
However, by the next day, he had recovered his composure. On returning to the UK, he sent the Polish a message expressing his sincere gratitude to them:
“Serdecznie dziękuję za współpracę i cierpliwość” (“My sincere thanks for your cooperation and patience”)
Shortly after the Pyry meeting, the Polish made good their promise to deliver a working Enigma replica to the British and the French. It is estimated that, with this act of magnanimity, they helped to shorten the Second World War by two to three years and save well over a million lives.
Following the Pyry meeting, the Bletchley team started recruiting some of the UK’s finest mathematical minds, including Alan Turing and Gordon Welchman. After Poland was invaded in 1940, Rejewski escaped to France, where he met Turing (who had not been to the Pyry meeting); when all of France was eventually overrun, he and his team had to escape again, reaching England in July 1943.
Rejewski took the risk of returning to Poland after the war ended in 1945; his wife, his two children and his parents, who had not seen him for six years, were waiting for him. Back home, however, Rejewski faced a communist regime that wanted to find out what he and his former colleagues had been ‘up to’ before and during the war.
He took a fairly lowly job well below his capabilities – perhaps to mislead the communist authorities into thinking that he could never have been the man who ‘cracked’ Enigma. He kept his secret safe from the Polish authorities
until 1976, when the Polish Cipher Bureau’s work before and during the war was revealed. Rejewski was then aged 61 and close to retirement, but at last felt sufficiently ‘bulletproof’ to reveal his role.
When the truth came out, the Polish cryptographers could finally enjoy the many honours and accolades bestowed on them. Memorials were established in Poland to Rejewski and other Polish mathematicians involved in cracking Enigma, such as Henryk Zygalski and Jerzy Różycki, as well as at Bletchley Park. This was appropriate, as these were the people to whom the UK owed so much for its wartime survival.
Rejewski himself received one of Poland’s highest honours, the Grand Cross of the Order of Polonia Restituta. He died in Warsaw in 1980.
David Forfar is a consulting actuary