Unbreakable. The Spies Who Cracked the Nazi's Secret Code by Rebecca E. F. Barone

Unbreakable tells the remarkable story of how the British, French and Polish worked to break the Enigma code, helping the Allies to win World War II.

The story opens in Warsaw, Poland in 1929.  A "heavy package with a German postmark" arrived at the Polish customs office. Almost immediately, an urgent request came in from the German embassy to return the package which should never have been sent to Poland as it was intended for a German recipient. His curiosity piqued, the Polish customs officer opened the package and found what at first glance looked to be a typewriter. However, there was no ribbon, no carriage to hold paper like a regular typewriter. There were keys which when pressed lit up one of the small circular windows arranged in rows at the top. The Polish customs officer called the Polish cipher agency and two men arrived to examine the machine. Over the weekend they took the machine apart, examined it and reassembled it. It was repackaged and returned to Germany, the delay being that it was the weekend.

Two years later on November 1, 1931, Hans-Thilo Schmidt met up with Rodolphe Lemoine, in the Grand Hotel in Verviers, Belgium. Schmidt was an assistant to the head of the Germain cipher office while Lemoine was the top recruiter and handler for the Deuxieme Bureau of the French military intelligence. Germany had developed a new cipher that no one in the world was able to break. They were using a machine called the Enigma to create the code and it was unbreakable.  Schmidt told Lemoine that he had access to all the information pertaining to Enigma and could give it to France, for a price. When Schmidt began bringing information to France, Captain Gustave Bertrand, a senior officer and a code breaker became involved. The initial information Schmidt brought was not helpful to either the French or the British in solving the Enigma problem. 

Undaunted, Bertrand travelled to Warsaw, Poland in December, 1931 to meet with Major Gwido Langer, head of the Polish cipher office, in the hopes the Polish and French might work together. Bertrand gave Langer the Enigma manuals and instructions that Schmidt had passed along. Langer was ecstatic because up to this point they had been unable to crack Enigma and he had high hopes this new information would help.

 

The Enigma was complex machine in which an electrical signal passed from the keyboard to a plugboard connected to pairs of letters and then to three (or more) rotors and onto a reflecting drum which sent the signal back through the rotors, plugboard to a window at the top of the machine with a letter. Each letter in a message when through this encryption. In order to decode the message, the settings in the Enigma machine of the receiver had to be the same as those of the sender's Enigma. The daily indicator settings for the rotors consisted of three letters, one for each rotor that gave the starting angle for each rotor were sent TWICE at the beginning of the message, unencrypted. These daily settings were called the key.

Meanwhile in Germany in November, 1932 political events were beginning to move quickly. Adolf Hitler had been arrested for the Munich Beer Hall Putsch years ago in 1924 on charges of high treason. He was given a lenient nine month sentence during which time he wrote his infamous Mein Kampf. In this book, Hitler outlined his plans to recover Germany's glory and eliminate the Jews and Polish people whom he considered "inferior races". Germany's problems were all due to the presence of Jews in the country and the world. In the following years, Hitler began to spread his message throughout Germany, that certain races and religions were responsible for the dire economic situation in the country. His political power grew until the Nazis held almost a third of the seats in the German government.

In November, 1932, in Warsaw, Poland, Langer's cipher staff were unsuccessful so he decided to try a new approach: he hired electronics expert Antoni Palluth, one of the two men who had examined the missing Enigma in 1929 and built a replica. He brought along Maksymilian Ciezki, head of the German section of the Polish cipher office. These two men brought in three young mathematicians, Marian Rejewski, Henryk Zygalski and Jerzy Rozycki. Langer's approach changed from linguistics to mathematics and it paid off. 

Working on his own, Rejewski initially had no success using variables and developing mathematical equations that explained how changes to the rotors or the plugboard affected one another. But then Schmidt gave Bertrand "...a photocopy of two tables of the keys for September and October, 1932". Bertrand passed these on to Langer who gave them to Ciezki and then to Rejewski.  At first it seemed like these did not help either, but then Rejewski decided to make a different guess about the Enigma keyboard which was arranged similar to that of a typewriter except adapted for the German language. Instead he wondered if the letters on the typewriter keys were arranged in alphabetical order. When he did this, all his equations worked and the Poles were able to read the German Enigma! It was January, 1933.

But the Polish ciphers had their work cut out for them. With Germany preparing for war, German military and civilian groups, each called a "net", were now using Enigma to send messages. Each net began using different keys and the Polish cipher team had to break each key for each net every day. This exhausting work went on for five years at Saxon Palace in Warsaw. As tensions increased between Germany and Poland, Langer decided to move the cipher team to the Kabaty Woods, ten miles outside of Warsaw to a new built complex called "the Gale". The code breaking continued but was so tedious that Rejewski developed a machine called a bomba, with switches and rotors "that could run through all the combinations from a known rotor starting point."

In Germany the situation continued to worsen.  In March, 1938, Lemoine was picked up the Gestapo and released, German troops crossed into Austria in the Anschluss, the Annexation of Austria, and in September 1938, the Sudetenland area of Czechoslovakia was annexed by Germany. Then in December, 1938, the Germans increased the number of rotors used in Enigma making determining the keys very difficult. 

The English and French still did not know the Polish had been able to read Enigma and their efforts were unsuccessful. Their meeting in Paris, France with the Polish revealed nothing. After Germany invaded Prague Czechoslovakia, Lithuania and Slovakia, Alastair Denniston (head of British codebreaking) and Alfred Dillwyn Knox met with Bertrand, Langer and the Polish cipher team. There they learned that the Poles had broken Enigma years earlier and they obtained a replica of Enigma.

With the British, French and Polish codebreakers struggling to catch up and find a way to break open Enigma, open war began with the invasion of Poland on September 1, 1939. As British codebreakers took up the task of deciphering Enigma, the British navy also set about obtaining any information they could from captured weather boats and sinking U-boats. The race was on to defeat Enigma and win the war.

Discussion

 

Unbreakable is the riveting account of the race by the Allies to unlock the German's Enigma coding machine. Barone masterfully guides her readers through this complex story that involves so many people, some of whom lost their lives to the cause.

Barone pieces together the contributions many Polish, French and British made in the race to break Enigma. Barone, in her Epilogue writes, 

"Breaking the naval Enigma was a testament to teamwork. There was not one hero, not even on team of heroes. The Enigma story played out over the course of more than a decade, with action spread throughout almost a dozen countries: Polish cryptologists worked early and long to crack the Enigma cipher; French and German spies and agents provided intelligence; British codebreakers took up the puzzle; naval ships and sailors seized codebooks from the U-boats; intercept stations relayed messages; and Wrens at the bombes actually ran the machines."

Her cast of characters includes not just the codebreakers like the Polish team of Rejewski, Zygalski, Rozycki, Langer, Ciezki and Palluth, and the British team of Alan Turing who developed the "cryptological bombe", Harry Hinsley, Hugh Alexander, and Gordon Welchman who devised a way to configure the wiring of Turing's bombe, and Joan Clarke. Many others took risks that sometimes cost them their lives. There were the over sixteen hundred "Wrens" (Women's Royal Navy Service) whose task was to operate and maintain the more than two hundred bombes, a physically challenging task that could easily cause a short circuit. There was Gunner "Florrie" Foord who rescued a bag containing "cribs"  and plugboard settings that allowed Turing to set his bombe to work solving the naval Enigma. And there was First Lieutenant Tony Fasson and sailor Colin Grazier who rescued codebooks from the sinking U-boat U-559 at the expense of their lives, codebooks that ultimately broke the naval Enigma. 

Unbreakable manages to explain the workings of Enigma and how it was deciphered in a way that is understandable and engaging to readers. It was a complicated machine and breaking it was not a one step task, but involved many attempts and innovations by the codebreakers.  The story is broken up into four parts, with short chapters, focusing on a single topic with some black and white photographs. Some chapters focus on events while others on specific individuals such as Joan Clarke.

Barone includes an Epilogue in which she informs readers as to the fate of some of the individuals she focused on, a detailed Timeline of events beginning in 1929, and extensive Bibliography for further research. There are also Endnotes providing sources to quotes used throughout the text.

Unbreakable is a fascinating account of the efforts of codebreakers, military men, and spies to crack Enigma which was considered unbreakable by the Germans. 

Book Details:

Unbreakable: The Spies Who Cracked the Nazi's Secret Code by Rebecca E.F. Barone
New York: Henry Holt and Company   2022

260 pp.