It might surprise you to know that when Alan Turing and his fellow brainiacs turned their
attention to cracking Enigma, they weren’t starting from scratch. Enigma had already been
broken, and broken, and broken again in the years leading up to the Second World War. This
tremendous feat was achieved by a small team of Polish mathematicians who, though often forgotten,
laid the foundations for one of the most important intelligence projects of the Second World War.
It might surprise you to know that when Alan Turing and his fellow brainiacs turned
their attention to cracking Enigma, they weren’t starting from scratch. Enigma had already been
broken, and broken, and broken again in the years leading up to the Second World War. This
tremendous feat was achieved by a small team of Polish mathematicians who, though often forgotten,
laid the foundations for one of the most important intelligence projects of the Second World War. but
the officers were STILL sending orders out over the radio with barely any encryption. In the words
of Polish Colonel Mieczysław Ścieżyński: “Messages [were] being transmitted either
entirely [plaintext] or encrypted by means of such an incredibly uncomplicated system that[,]
for our trained specialists reading the messages[,] was child's play.”
In Poland, the Army’s Cipher Section picked up these Soviet transmissions, and it wasn’t long
before they cracked the codes. Three months after the Polish-Soviet War began in February, Polish
High Command was fully aware of Soviet battle plans — sometimes before Soviet soldiers were!
Towards the end of the war, defeat after defeat was inflicted on the Bolsheviks and, largely due
to Cipher Section intelligence, the Polish were able to snag some serious peace deal concessions.
In early 1928, a mysterious package arrived at the Warsaw Customs Office. It was from Germany
and apparently contained radio equipment. The officials thought nothing of it… until the
manufacturer got in touch and demanded the package be sent back immediately — without inspection.
Naturally, the Poles were curious and opened the box, only to find a machine they didn’t recognise.
A team from Cipher Section were called in to examine it, and they were fascinated. It was
an early commercial Enigma machine. After taking detailed notes on its operation, the machine was
sent back to Germany as ordered, but now, Cipher Section knew the Germans were up to something.
In the early 1930s, the German military began using modified Enigma machines,
like the one from the Customs Office, to transmit encrypted messages. Throughout the decade,
German manufacturers secretly improved Enigma’s design. Even with their extensive prior knowledge,
messages sent on later Enigma machines confounded Polish codebreakers.
Remembering the role intelligence played in their victory during the Polish-Soviet War,
the Polish Army decided to throw its weight behind the codebreakers at Cipher Section.
They got a budget increase, several hand-picked mathematicians from Poznan University,
and were renamed to Cipher Bureau. One of their new recruits was Marian Rejewski, who began
working for the Army as a cryptologist in 1930. Having had their eyes on Rejewski for some time,
the Polish intelligence service offered him, and several others, a spot on a secret
cryptography training course. The workload was immense, and only three students passed.
In 1932, Enigma transmissions were becoming increasingly frequent, and the Poles were,
rightfully, getting nervous. Time was wearing on, and they were no closer to cracking the machine’s
secrets. That was until Rejewski started working on it. After taking one look at
Cipher Bureau’s methods, he scrapped them. These old methods relied on letter-frequency analysis
and linguistic patterns to break the cipher. For example, E is the most common letter in
German and appears around 17% of the time. So the Poles expected to find a substitute letter for E
around 17% of the time too. Great in principle, but not when it comes to Enigma.
In an Enigma machine, E could become several different letters, which messed up the
probabilities. Additionally, several different letters could all come out of the machine as an E,
making things even tougher for the codebreakers. But this is where Rejewski’s theorem came in.
Using pure mathematics, something that had never been done before in cryptography,
Rejewski put together a theorem that explained the relationships between
letters inside the Enigma machine. It was
groundbreaking stuff and has even been touted as "the theorem that won World War II."
But Rejewski wasn’t working alone; he had some serious help. Not from other codebreakers,
as few could match his mathematical skill, but from the French, who were neck-deep in espionage.
Happy to help out anyone working against the Germans, the French intelligence service passed
top-secret Enigma documents on to the Polish codebreakers.
But where did they get the documents?
Hans-Thilo Schmidt, the brother of Wehrmacht General Rudolf Schmidt, lived quite an extravagant
life. He greatly enjoyed throwing large sums of money around and generally playing the role of a
big shot. Sadly, the meagre salary he earned from his position in the German Armed Forces’ Cipher
Office just wouldn’t cover his expenses. Unlike his brother, Hans was no friend to the Nazis and
believed they were ruining Germany. To get back at them and fund his high-rolling at the same time,
Hans offered to sell Enigma documents to French Intelligence.
He was given the codename “Asché,” and his secrets were passed onto Gustave Bertrand,
the head of French radio intelligence, who in turn passed them on to the Polish mathematicians.
For the Poles, these documents proved to be a goldmine. Asché provided them with Cipher keys,
duplicate plaintext and encoded messages, and even instructions for operating an Enigma machine.
Combined with what they already knew about Enigma, the Poles had all they needed to crack the code.
By early 1933, Polish Cipher Bureau was regularly decrypting German radio traffic. So long as
documents from Asché kept coming, they could keep up with everything the German military was up to.
But Asché wouldn’t be around forever. One mistake could land their German mole
in a Gestapo torture chamber, and leave the Poles in the dark again.
But luckily for the Allies, Asché was careful. Multiple Gestapo investigations
sought to discover the source of radio intelligence leaks before the war started,
but they never suspected Hans. As the brother of a respected general, he was politically
untouchable. Hans knew his connections were buying him out of trouble, but he still enjoyed
seeing the Gestapo crawl around looking for traitors, only to come back with nothing.
From 1936-onwards, German high command began
implementing new procedures that made Enigma drastically harder to break.
They reset the plugboards more often, switched the rotor positions daily, and tightened up
radio net security. New techniques had to be developed by the codebreakers,
and they were successful, but it was taking them longer and longer to break the encryption.
To expedite the process, Rejewski designed and built an electro-mechanical machine
called “Bomba.” It was essentially an aggregate of six Enigma machines
and was used together with the traditional longhand methods.
With an efficient team, Bomba could work out the daily Enigma cipher key in about two hours.
This feat of engineering kept Polish generals informed of virtually ALL German plans. When the
Wehrmacht invaded on September first, Polish High Command knew 95% of the German order of battle.
Knowing what the Germans were planning, Polish High Command ordered Cipher Bureau give all
the intelligence it had to French and British representatives in July 1939. Rejewski and his
mathematicians handed over a reconstructed Enigma machine, a Bomba, instructions on how to break the
code longhand, and records of German intercepts to both countries. “The Gift,” as it was called,
represented Poland passing the codebreaking baton to France and Britain for the rest of the war.
During the handover, a British officer asked Rejewski the most pressing question
everybody had about the Enigma machine: how were the letters arranged on the entry drum?
This question confounded the Brits for years,
but for the Poles, it was obvious. They guessed that the well-ordered Germans would organise
everything in alphabetical order. They were correct, and the Brits were dumbfounded.
When Poland was lost to the German advance, Cipher Bureau burned all its documents and destroyed all
its equipment. But their vital contribution to the war effort lived on in England. Gordon Welchman,
a Bletchley Park mathematician and cryptologist, stated: "Ultra [the Enigma codebreaking project]
would never have gotten off the ground if we had not learned from the Poles, in the nick of time,
the details ... of the ... Enigma machine, and of the operating procedures that were in use."
Captured, tortured, and executed, none of those who worked at Cipher Bureau spilled the beans
about their discoveries. Most were killed in prison camps during the later years of the war,
and their enduring silence allowed their comrades overseas
to capitalise on a decade of Polish codebreaking work.
THAT was the story of the Polish mathematicians who first broke Enigma and laid the foundation for
the most important intelligence operation of the entire Second World War. But what do YOU think?
Are YOU surprised the Germans wired their machine up in alphabetical order?
Did YOU know Enigma was broken as far back as 1932? How much longer do YOU think it
would have taken to break the code had Hans not sold out the Nazis? Let us know in the comments!