Thomas Sanger

Fritz-Julius Lemp, U-30 commander, confers with Karl Doenitz, chief of U-boat operations. Photo credit: Galway Advertiser

Why Don’t We Remember Athenia? Part 2

by Thomas Sanger • Thomas C. Sanger • Leave a Comment

When Oberleutnant Fritz-Julius Lemp torpedoed and sank the British passenger ship Athenia at the beginning of World War II, he did not break radio silence to report his attack to his superiors. His decision led Germany’s Nazi government to deny responsibility for the sinking, a position they maintained for the duration of the war. That denial is undoubtedly a factor contributing to Athenia’s relative obscurity in historical accounts of the war (see blog, Nov. 30, 2018). 

The war was not quite nine hours old on Sept. 3, 1939, when Lemp, in command of U-30, torpedoed what he believed was a legitimate wartime target – an armed merchant cruiser. When he came to the surface after nightfall to assess how fast the ship was sinking, he discovered he had attacked an unarmed passenger ship, exactly the type of target his operational orders told him to avoid.

Lemp left the scene without breaking radio silence because, he later said, he did not want to betray his position to the British. Whatever Lemp’s reason for not reporting his action, it caught the German government flat-footed the next morning when news of a U-boat attack on an unarmed passenger ship began to circulate. Nazi officials immediately checked with naval authorities and received assurances that no U-boats had reported any action in the vicinity of the incident, which was correct but misleading.  Some U-boats had not reported at all, including U-30.  

The Nazis were eager to deny responsibility for the sinking because it gave England a major propaganda tool to use against Germany. Far worse, however, was the possibility that the attack on Athenia had killed Americans, which might bring the United States into the war. Germany’s Secretary of State for Foreign Affairs wasted no time the morning of Sept. 4, 1939, in offering Americans an official German denial of any responsibility for sinking Athenia. To assure world opinion that Germany was abiding by international treaties, Chancellor Adolf Hitler issued an order to all naval units that same day, warning that no passenger ships were to be attacked under any circumstances.

When Athenia survivors began disembarking in Galway and Glasgow a day later, they made it clear they thought their ship had been torpedoed and several said they had seen the submarine. In response the German press speculated Athenia may have been mistakenly attacked by a British submarine or had struck a floating mine. Within days, however, the Nazi’s chief propagandist, Joseph Goebbels, published an account that Britain’s new First Lord of the Admiralty, Winston Churchill, had planted a bomb on board Athenia in order to sink the ship, kill American passengers, and bring the United States into the war against Germany. 

Britain vehemently denied the allegations and few outside of Germany believed the Nazi assertions. Even so, the United States, which announced it would be a neutral party in newly declared war, refrained from blaming Germany in the absence of irrefutable proof, a sign of the isolationists’ political strength in the U.S.

The Churchill story had been circulating for two weeks when Lemp returned to his base in Wilhelmshaven and reported to Karl Dӧnitz, Germany’s submarine fleet commander, that he sank Athenia. At Hitler’s direction, German officials continued to deny responsibility for Athenia’s sinking through the remainder of the war.

In next month’s blog: The truth is finally revealed.

Young Athenia survivor arrives in Glaway, Ireland. Photo credit: The Telegraph

Why Don’t We Remember Athenia? Part 1

by Thomas Sanger • Thomas C. Sanger • Leave a Comment

The Second World War was a little less than nine hours old on Sept. 3, 1939, when a German submarine torpedoed and sank the unarmed British passenger ship Athenia. The incident not only was the opening shot of World War II’s longest continuous conflict – the Battle of the Atlantic – but also made Athenia the first British ship sunk by Germany in the war.

Seventy-nine years later very few people on either side of the Atlantic have ever heard of Athenia or know of the ship’s place in history. How such a singular moment could have faded from our collective memory is a question we will explore in my next four monthly blogs, beginning today.

The first of several factors helping to eclipse Athenia’s memory is the death toll: 112 men, women, and children died as a result of the U-boat attack. In 1915, during World War I, nearly 1,200 passengers and crew members died when the British liner Lusitania was torpedoed by a German U-boat. With a death toll more than ten times greater than that of Athenia’s, the Lusitania sinking is seared into the history books of World War I.

Like the peacetime tragedy of the Titanic, who’s sinking had claimed more than 1,500 lives in 1912, human beings seem prone to remember these greater catastrophes. Fortunately for most of the people aboard Athenia, the death toll from her sinking failed to reach such a threshold.

While U-30 fired at least three torpedoes at Athenia that fateful Sunday evening, only one struck home. It proved to be a mortal blow, but the ship remained afloat for nearly fifteen hours, more than enough time for her crew to launch all twenty-six lifeboats.

The launching process was complicated by the fact that the ship began listing to her port side, making it more difficult to lower the boats on her starboard side where they scraped down the hull on the way to the water. During the hour and twenty minutes it took to launch the boats, Athenia’s portside tilt held at a manageable five to six degrees.

Also assisting in the launching conditions was the fact that the Atlantic Ocean was relatively calm for early September. The wind would rise steadily through the night and into the following day, but it was not a factor for the first several hours after Athenia was torpedoed. The ship’s lifeboats were launched by hand, a process that would have been complicated had the seas been higher, particularly as Athenia’s engines had been knocked out and the ship would have been at the mercy of the ocean’s swells.

In the end, all but two of the ship’s twenty-six lifeboats made it through the night without mishap. Rescue ships responded quickly to Athenia’s S-O-S, the first appearing on the scene about six hours after the torpedo strike.

All of these conditions, plus the crew’s training and flawless execution of their duties, meant that the sinking of Athenia was not nearly the tragedy it might have been, one important reason why the ship’s loss has faded into history’s shadows.

In our next blog: Germany denies responsibility for the sinking.

Could you understand this Middle English conversation? Photo credit: NPR

Challenges of Historical Fiction Dialogue

by Thomas Sanger • Thomas C. Sanger • Leave a Comment

When an author tackles a subject of historical fiction, a number of considerations come into play. What are the living conditions the characters will experience for the given time period? What key details will make the period come alive for the reader: food, clothing, transportation, political/historical conditions, religious beliefs, medical or scientific knowledge?

Depending on the time period, most of these details are available in resources found in libraries, museums, and archives. But what does an author do about dialogue? In a novel, characters are going to speak to each other, and in some cases may even narrate the story. Making that language sound authentic is a critical element for bringing the reader into a historical novel’s timeframe.

To manage this feat, many historical novelists immerse themselves in the language of the period they are writing about. They absorb speech patterns, syntax, and any distinctive words that call to mind a particular time or place. For most of the 20th century there are multiple dialogue examples: radio and television transcripts and recordings, movies, books (including other novels), newspapers, speeches, letters, and diaries. These sources begin to drop away as the centuries recede, so the further back in time the story is set, the greater the challenge.

And yet, authors like Ken Follett, Bernard Cornwell, and Philippa Gregory manage to write hugely successful novels set in ancient times. How do they do it?

Fortunately, the historical novelist doesn’t need—and shouldn’t try—to exactly replicate the speech of a bygone era. Anyone who has struggled to read the Middle English of Geoffrey Chaucer understands that a novel set in the 14th century would bog down under the pretense of “authentic” dialogue. Regardless of a story’s historical setting, its characters’ dialogue must communicate with today’s readers.

Once an author becomes familiar with the language of a particular era, the task is to write dialogue that sounds authentic to the period, even though it primarily makes use of language familiar to current readers. The most obvious concern is to keep current slang or figures of speech out of the mouths of characters living decades or centuries before present day. Altering the syntax just enough to emulate the novel’s period gives it a feeling of authenticity. Likewise, having characters use a few unfamiliar words or idioms from the period can help dialogue ring true, but only if the meanings can be readily inferred by the reader.

As with any novel, the dialogue should never call attention to itself or cause the reader to step back from the narrative to wonder if a character would actually say what the author has written. The best dialogue is short and to the point. It uses common, everyday words to communicate information, ideas and emotions. To meet these guidelines and make the dialogue sound as if it is spoken by 12 century serfs or 18th century nobility, is a remarkable feat.

So the next time you read a historical novel whose characters convey powerful ideas and emotions in a vernacular that sounds authentic to the period, you can appreciate even more the artistry that goes into the work.

Sub-Lieutenant David E. Balme, R.N. Photo credit: The Telegraph

Enigma’s Mysteries Revealed

by Thomas Sanger • Thomas C. Sanger • Leave a Comment

Nearly two years after the start of World War II, the British Royal Navy for the first time put a boarding party onto a crippled German submarine. On May 9, 1942, 20-year-old sub-lieutenant David Balme led a party of nine sailors onto U-110, not knowing if the boat had been booby-trapped and half expecting scuttling charges to detonate at any moment.

Balme and his men had been sent across from H.M.S. Bulldog by her captain, Commander Joe Baker-Cresswell, with orders to gather up signal books and any other useful materials they might find (see blog post “Lemp’s Fatal Mistake, Aug. 30, 2018). Balme was the first man into the submarine, and when he was certain the boat had been abandoned, he called for the rest of the men to join him in the U-boat’s control room.

“The lights were still on and everything was lying about just as if one had arrived at someone’s house after breakfast, before they had had time to make beds, etc., coats were thrown around, bunks half made,” he later remembered. “There was complete silence in the U-boat except for the continual thud of our own depth charges [in pursuit of a second U-boat]…a most unpleasant and frightening noise.”

He told the men to ignore anything that was obviously casual reading material and to take whatever else appeared to be of interest. Speed was of the essence because U-110 was sinking and Balme was still concerned about explosive charges. Complicating matters was the fact that none of the men read German.

At one point, a sailor came out of the U-boat’s radio room and told Balme, “There’s something rather interesting I want to show you.” In the cramped radio room, Balme was shown a typewriter-like device screwed to the table. He could see that pressing one key on the machine caused a different letter to light up on a display. Balme told the sailor to unscrew it and send it up with the rest of the material being gathered. The young sub-lieutenant had no way of knowing that his party had just recovered the first working model of the German naval Enigma machine, a top-secret prize British Intelligence had coveted since the start of the war.

As the day wore on and the submarine remained afloat, Balme became less concerned about scuttling charges or the boat’s quick demise. At one point, Bulldog sent over sandwiches and a small boat to replace the one that had smashed itself on the U-110’s deck. He did worry, however, when Bulldog was called away on a U-boat sighting and a dense fog settled on the ocean.

“There was I, with my boarding party aboard U-110 in the middle of the Atlantic, alone with no ships in sight and with the wind and sea gradually increasing,” Balme recalled. Fortunately, Baker-Cresswell’s dead-reckoning navigation skills brought Bulldog back to the crippled submarine before nightfall, and the treasure trove of materials, including the Enigma machine and its codebooks, were transferred to the British destroyer.

By day’s end, Bulldog took U-110 under tow in hopes of delivering her to Iceland for careful inspection by British submarine experts. The next day, however, the U-boat sank en route. By then, the submarine’s capture and its trove of materials had been given a top-secret designation with the code name “Primrose.” Great effort went into limiting the number of people made aware of Primrose, and the capture was kept secret for several decades after the war.

U-110’s sinking may have been a blessing in disguise. Had the boat been towed to Iceland, it is entirely possible that local German spies would have relayed its capture to German authorities. German naval commanders would have assumed their encrypted communications could be compromised and they would have made changes to the Enigma machine and its codes much sooner than was actually the case. Even after the Germans made modifications in an effort to restore the naval Enigma’s integrity, insights gained by British intelligence from the materials taken from U-110 helped reduce code-breaking to a matter of hours or days instead or weeks.

At least one naval historian went so far as to characterize Operation Primrose on a scale commensurate with the outcomes of the Battle of Midway in the Pacific and the Battle of Stalingrad in Europe – not a bad day’s work for a Royal Navy convoy escort group and a junior naval officer barely out of his teens.

Crew from H.M.S. Bulldog prepares to board U-110 Photo credit: Wikipedia

Lemp’s Fatal Mistake

by Thomas Sanger • Thomas C. Sanger • Leave a Comment

The man who sank the unarmed British passenger ship Athenia on the first day of World War II, Kapitanleutnant Fritz-Julius Lemp, had managed to become a “U-boat Ace” in the 20 months of the war since his tragic mistake. Lemp had been credited with 22 ships sunk or damaged and awarded the Knights Cross, Germany’s highest award for valor. But in May of 1941 the brash, young U-boat commander’s luck was about to run out.

Two days after the Enigma code books for June were taken off the German trawler München (see blog post for Aug. 6. 2018), Lemp, now in command of U-110, attacked a westbound convoy off Greenland in the middle of the day. He fired a fan of four torpedoes at a horizon filled with Allied ships. Two shots struck home, adding two ships to Lemp’s tally. His third torpedo missed, and the fourth failed to launch from its tube. As Lemp waited at periscope depth to reset his forth torpedo for another shot, he was discovered by a British corvette that crippled U-110 with a depth charge attack.

Commander Joe Baker-Cresswell, the man in charge of the convoy escorts, was surprised to see U-110 pop to the surface in front of his flagship, H.M.S. Bulldog. He ordered his destroyer ahead at full speed, intent on ramming the U-boat, but thought better of it when he realized the Germans were abandoning ship. At almost that same instant, Kapitanleutnant Lemp was telling his radio operator not to worry about destroying the boat’s Enigma machine and code books, and to get off the ship immediately because it was sinking.

But U-110 did not sink, at least not immediately. Sensing a unique opportunity, Baker-Cresswell brought Bulldog to a stop just near U-boat He put David Balme, a 20-year-old sub-lieutenant, in charge of a boarding party and sent them off in small boat with instructions to gather up any signal books he could find on the submarine.

When they were nearly alongside the U-boat, their small boat was swept up by a large swell and smashed onto U-110’s deck. The men scrambled out onto the U-boat and climbed to the top of the conning tower, where Balme was surprised to find the entry hatch closed tight. Why close a hatch if the boat was intended to sink, he wondered? He opened the hatch and had to holster his revolver to climb down the ladder, feeling totally exposed if any Germans were still aboard.

“This was a nasty moment,” Balme later wrote, “one looked down below and wondered how many Germans were there. I went down the ladder to the lower conning tower where there was a similar closed hatch. On opening this hatch I found the control room deserted! Hatches leading forward and aft were open and all lighting on.”

He could hear air escaping somewhere in the U-boat, but there was no hint of chlorine, a deadly gas that could be produced by the boat’s batteries being submerged in seawater. For young Balme, the discoveries were just beginning, as we will see in our next blog.

German trawler Munchen is captured by a British destroyer. Photo credit: Warcovers website

Sea Battles Turn Tide of Events for Enigma Codebreakers

by Thomas Sanger • Thomas C. Sanger • Leave a Comment

After a brief lull in the Battle of the Atlantic during January, 1941, German U-boats began to sink increasing numbers of Allied ships: 47 ships in February and 50 ships in March. But in March, a naval engagement off the coast of Norway was about to produce a valuable prize for Britain’s Bletchley Park code breakers. (See my blog, “Decoding Enigma: Success and Setback,” June 18, 2018.)

During a March 4th British commando raid, a Royal Navy destroyer engaged in a brief gun battle that left a German trawler disabled and burning. While the Germans abandoned their crippled ship, a three-man boarding party went across to the trawler. The leader of the party, Lt. Sir Marshall Warmington, broke into a locked desk in the captain’s quarters and found a wooden box containing two small, ratcheted wheels. Although he hadn’t been briefed on the German Navy’s Enigma coding device, Warmington thought the box looked intriguing. He retrieved it and some unimportant looking papers.

The papers turned out to be a bonanza for the Bletchley cryptanalysts. They contained Enigma settings for February, helping the analysts read several encoded German Navy messages from the previous month. With the help of these “cribs,” the analysts were able to construct the German bi-gram (two-letter) table used in transmitting the Enigma settings for individual messages. Even with this advantage, however, the decoding process still took weeks to complete.

To speed up the process, the Royal Navy quietly began putting together plans to capture a U-boat or other German naval vessel in hopes of obtaining more current Enigma codebooks. Thus far in the war, however, the Royal Navy had realized only limited success in sinking U-boats, let alone capturing one.

At this point, a radio traffic analyst at Bletchley Park proposed an inspired solution. In looking through the decrypted messages, Harry Hinsley saw that the Germans were sending trawlers to the seas north of Iceland to observe and report the weather conditions back to naval headquarters. Hinsley believed these lonely ships were equipped with Enigma machines and codebooks in order to send and receive certain secret messages. If such a ship suddenly came under attack, he reasoned, the crew might think to throw overboard their Enigma device and current codebooks, but likely would be too panicked to take the time to retrieve and destroy the next month’s codes, locked away for safekeeping.

The plan worked exactly as envisioned. On the afternoon of May 7, 1941, a Royal Navy destroyer opened fire as it raced toward the German trawler München. Moments after the trawler’s crew were picked up by the British, a boarding party from the destroyer climbed aboard the München, and this time they were joined by a London-based Intelligence officer who had been told what to look for and where he was likely to find it.

As expected, München’s crew had disposed of the Enigma machine and current codebooks, but not the codebooks for June. Three days later, the June codes were delivered to cryptanalysts at Bletchley, a gift that would allow them to read the German Navy’s June radio traffic within hours of it being sent.

Yet even as this operation was being hailed, another trove of information was falling into Royal Navy hands, courtesy of the same U-boat commander whose attack on the passenger ship Athenia had begun the Battle of the Atlantic 20 months earlier. More about that dramatic action in our next blog.

Alan Turing, one of the leading British cryptanalysts at Bletchley Park. Photo credit: A & E Biography

Decoding Enigma: Success and Setback

by Thomas Sanger • Thomas C. Sanger • Leave a Comment

By the spring of 1940, British cryptographers had a general idea of how the German Naval Enigma cypher device worked, but could not break its code without “cribs” ( see my blog, “British Codebreaking and the Bletchley Park Connection,” May 31, 2018).

To read the Naval Enigma messages, Bletchley Park analysts needed to know identity and order of the three wheels used to send messages, plus the settings on the wheels, and the plugboard setup for the day the message was sent. All this information had to be transmitted to the Enigma operators in the field before they could decode messages. The question was, how did the operators obtain the information?

A significant breakthrough happened in late April when a Royal Navy destroyer captured a German trawler off the Norwegian coast. The Germans had managed to throw two bags overboard filled with codebooks and the ship’s Enigma device. The bag with the Enigma sank, but the second bag did not and was recovered.

That second bag contained coded messages along with their related plain text translations (valuable cribs needed to help break the Naval code). This information, along with the Enigma wheel and plugboard settings for two of the days, allowed Alan Turing and his associates to read the first German Naval messages since the start of the war, albeit nearly two weeks after they were sent. However, access to these messages helped Turing work out how the Naval Enigma indicators were sent (see my May 31, 2018, blog).

To read the messages in real time, the codebreakers would need a copy of the bigram (a two-letter configuration) table used to send the messages, and no bigram tables were recovered from the trawler. Undaunted, British cryptanalysts were able to use the cribs to work backwards and begin to fill in the bigram pairings. With enough cribs, they were able to reconstruct most of the bigram table in use at that time.

Turing devised a system to help eliminate most of the wheel positions not used to encrypt a message. The smaller number of remaining possibilities could then be tested using his “bombe,” a pioneering computer that worked out the eventual correct wheel positions. Through this sped-up trial-and-error methodology, cryptanalysts were able to break a few months-old Naval Enigma messages without first having the wheel or plugboard settings.

But in decoding one of the messages, Turing discovered that a new bigram table would be introduced July 1, 1940. The change sent Bletchley Park’s Naval Enigma deciphering efforts nearly back to square one. Despite this setback, the British had developed more effective tools and methods for breaking the German Naval codes.

Now, however, the question was whether they would be able to read the German messages in real time before the rising U-boat toll could starve Britain into submission.

Bletchley Park estate, center of British WWII code breaking efforts. Photo credit: Art Fund

British Codebreaking and the Bletchley Park Connection

by Thomas Sanger • War History • Leave a Comment

As the German Army began invading Poland on Sept. 1, 1939, the Polish codebreakers prepared to vacate Warsaw. They were careful to take with them or destroy all evidence of their years of success in reading German military messages sent by the Enigma cypher device (see my blog, “The Evolution of Enigma,” May 16, 2018).

Two weeks later the Poles entered Rumania, took a train to Bucharest and contacted the French Embassy. By the beginning of October, they were safe in a French chateau about 25 miles northeast of Paris, along with two replica Enigma machines they had smuggled out of Poland. By now, however, the principal effort to decode Enigma was shifting across the English Channel to a country manor in Buckinghamshire, 50 miles northwest of London.

Bletchley Park, an ornate stone edifice set on 58 acres of private land, had become the new home of the British Government Code & Cypher School (GC&CS). Bletchley was considered a much safer wartime location than the school’s previous home in London.

The estate sat almost equidistant on the rail line between Oxford and Cambridge, the universities whose faculty members and top students would supply much of Britain’s codebreaking brainpower. To ramp up its efforts, the GC&CS had begun recruiting linguists, chess champions, cryptic crossword puzzlers, and mathematicians; people with skills uniquely suited to cryptanalysis.

Early efforts to read the German signals were fruitless, owing to the changes in coding procedures introduced prior to Germany’s Polish invasion. In early 1940, one of Britain’s top codebreakers, mathematician Alan Turing, visited his Polish cohorts in France and gained several key insights, including the wiring scheme for the German military Enigma. Within months of his return to Bletchley, Turing devised his initial electromechanical computing machine, which he called a “bombe.” His device helped defeat some of the new German cyphering practices..

By transmitting only once, instead of twice, the three-letter setting used to encode an Enigma message (see March 16 blog), the Germans had made it much more difficult for British codebreakers to work out the correct setting in a timely manner. Touring’s machine, however, sped up the process by quickly eliminating most of the unlikely three-letter sets.

By mid-1940 Bletchley cryptanalysts were reading the German Army and Air Force signals within days, or even hours, of receiving the coded messages. It helped that both services continued to use the same five wheels they had been using for years to make up the three-wheel combinations for their Enigma transmissions. The internal wiring of these five wheels had long-since been worked out by the Poles.

But the Naval Enigma signals remained a mystery. Instead of five wheels from which to choose, the Navy added three more individual wheels, greatly complicating Britain’s codebreaking efforts. Even more complicated was the way in which the Navy identified the three-letter settings (called “trigrams”) for encoding messages,

The process used a pre-determined list of three-letter indicators. The message sender chose one of these trigrams to encode the message and a second “dummy” trigram. The two trigrams, plus two random letters, were used to construct four two-letter “bigrams.” The sender then consulted a bigram table that showed a conversion for every possible bigram into a second, unrelated bigram. These eight letters were then sent by Morse code at the beginning of the message along with the enciphered message.

By the end of 1939, Turing believed he understood how this system worked to identify the trigram for each encoded naval message. But understanding the system did not allow him to read Navy Enigma signals without a copy of the bigram table.

By the summer of 1940, an enhanced version of Turing’s bombe was being built. If they had enough plain-text German Naval messages along with their encryptions (what cryptanalysts termed a “crib”), the “super bombe” could break the Naval Enigma. But it was a classic conundrum: without cribs they could not break Enigma messages, yet without breaking Enigma messages they could not obtain cribs.

There was, however, one other possibility, as we will see in our next blog. 

Photo caption: Dr. Arthur Scherbius, German electrical engineer who developed the Enigma machine. Photo credit: Alchetron

The Evolution of Enigma

by Thomas Sanger • Thomas C. Sanger • Leave a Comment

In my last blog (“The Mystery of Enigma,” May 1, 2018), we explored the ingenious design of the German Enigma machine. The encryption device provided so many possible permutations for each letter in a message that it seemed impossible for Enigma’s code to be broken.

Despite Enigma’s close association with World War II, the device actually was developed at the end of World War I. Arthur Scherbius, the German engineer who created the Enigma, sought to interest the German navy and the Foreign Office in his newly patented design in 1919, but both turned him down.

Scherbius formed a company and exhibited his first machine in 1924 at an international gathering of postal officials. That first model, marketed under the brand name “Enigma,” incorporated an actual typewriter, weighed just over 100 lbs., and lacked many of the refinements of later models.
By 1927 Scherbius designed a machine that was lighter and more portable. The new model proved popular, and the company sold Enigmas to commercial markets in Europe, Scandinavia, the United States, and Japan. At about the same time, the German navy and army acquired upgraded Enigmas that included the plugboard design, a feature not available on commercial models.
Over the next decade, the German military models underwent further tweaks and upgrades to become even more inscrutable than their commercial cousins. For example, the army’s Enigma version incorporated a fourth wheel, while the navy continued to use the three-wheel design but introduced two additional wheels that could be interchanged with any of the three original wheels.

Beginning in the late 1920’s military intelligence operations in Britain, France and Poland set about trying to break the German military Enigma code. They had no success until late 1931 when an executive in the German Defense Ministry began spying for the French and provided a copy of the Enigma instruction manual as well as three-letter codes used to set up the machines.

This material was passed by the French to the Poles, who were further along with their decryption efforts owing to the Poles’ greater affinity with German engineering and their proximity to a re-arming German state. Using the spy’s information, Polish mathematicians succeeded in working out the internal wiring of each of the Enigma wheels, and in 1933 Polish intelligence built several prototype Enigmas and began to read German military communications. The Poles, however, did not inform the French or British of their success.

Every day each branch of the German military set their Enigma machines to a pre-arranged master setting which included the order of the wheels, the setting of the initial letter on each wheel, and the plugboard connections. From this arrangement, the sender transmitted a new random three-letter code for the initial wheel settings then adjusted the machine’s wheels to the new settings and typed the message. The receiver decoded the initial three letters, re-set the receiving machine’s wheels accordingly and decoded the message that followed.

The Poles used an arrangement of six prototype Enigmas to determine the wheel positions of the German machines each day. To read individual messages, they relied on the German practice of repeating the random three-letter setting at the beginning of each transmission.
The Polish cryptographers were able to keep up with most German modifications, reading military communications for nearly five years. On the eve of World War II the Germans made physical changes to their Enigma machines and changed code-sending practices, leaving Polish intelligence unable to “eavesdrop” on the German military. The battle to solve Enigma shifted to a new front, as we’ll see in our next blog.

The German Enigma encryption device scrambled electrical impulses so that a different letter lit up than the letter on the key struck by the operator. Photo credit: Los Angeles Times

The Mystery of Enigma

by Thomas Sanger • Thomas C. Sanger • Leave a Comment

During World War II, German armed forces communicated via the now famous Enigma cipher device. The machine, about the size of a typewriter, encrypted messages that could not be deciphered except by another Enigma device. Both machines had to be calibrated with the same three-letter code for the system to work.

The Germans were so confident of their encryption system that they believed their enemies were incapable of breaking the Enigma code. Here’s why.

Enigma had a keyboard resembling that of a typewriter. Above the keyboard, where a typewriter’s keys would move to strike a letter on paper, the Enigma had a “lightboard.” The lightboard had the same arrangement of letters as the keyboard, with each letter able to light up individually. Striking a key on the keyboard caused a different letter to light up on the lightboard. This was because the keyboard key sent an electric impulse through a series of scrambling elements inside the Enigma before it reached a letter on the lightboard.

Above the lightboard, where a typewriter would have a platen roller to receive a piece of paper, Enigma had three wheels mounted side-by-side on a spindle. Each wheel was nearly four inches in diameter and had twenty-six electrical contact points that corresponded to the letters of the alphabet. The internal wiring of the wheels differed, so that one wheel might receive an electrical impulse through its letter “H” and output the impulse through a different letter, say its “C.” Each wheel thus scrambled the signal to change the letter.

The first wheel advanced to its next letter every time a key was struck on the keyboard. At some point in its rotation, the first wheel caused the second wheel to advance to its next letter. Likewise, the second wheel had a tripping point that caused the third wheel to advance one letter. After the impulse passed through the three wheels, a “reflector” sent the impulse back through the wheels via a different route. The reflector function made Enigma self-reciprocal, so that a receiving machine set up identical to the sending machine could decrypt the message.

The Enigma operator had five wheels from which to choose the three to place on the spindle. The wheels were designated by Roman numerals and each day, the wheels and their order on the spindle was changed, as was the starting letter setting for each wheel.

To complicate matters even more, Enigma had an additional scrambling element called a plugboard, which was located below the keyboard and resembled a small telephone switchboard. The plugboard mirrored the keyboard, with the twenty-six letters of the alphabet, each with a plug receptacle below it. The operator could randomly pair two letters by plugging a cable into each letter’s receptacle. As many as ten pairs of letters might be connected for the day’s setting.

Before the electrical impulse from the keyboard reached the first wheel, it went through the plugboard, where it might be changed to a different letter. Likewise, after the impulse went through the wheels it returned through the plugboard, possibly changing letters again, before going to the lightboard to cause a letter to light up.

The operator sending the message copied down the letters from the lightboard and transmitted them via Morse code in four- or five-letter groups. The operator on the receiving end keyed the letter groups into an Enigma machine with identical settings and copied down the letters appearing on the lightboard to decrypt the message.

The number of possible configurations totaled 3 X 10 with 114 zeros behind it. Small wonder, then, that the Germans considered their communications to be unbreakable.

Nevertheless, the Enigma code was broken. It was an effort that involved spies, cryptographers, mathematicians, and daring-do on the high seas, as we will see in succeeding blogs.