The code name for the British effort to crack the German military Enigma cipher machines was called Ultra. It was one of the most closely guarded secrets of the War. It was conducted at a country estate called Blechley Park. With the help of the Poles the British began working on the Enigma code machines that the German military used for radio communications. Effective German communications were part of the reason for the victories in Poland and France. The French General Staff for example was using messengers to communications. While effective, the use of messages sent by radio meant that German military communications were vulnerable. The German relying on their preceived notions of supperiority were convinced that their Enigma cipher machine could not be ceacked. The Germans did not know of the Allied success until well after the War. British code breakers at Bletchley Park faced different problems with the Wehrmacht, Luftwaffe, and Kriegsmarina code. The Luftwaffe code proved the easiest to crack, primarily because flushed with sucess, the Luftwaffe was careless about following established security procedures. Many messages were read because operators did not follow procedures. The British suceeded in dechipering some Luftwaffe messages (May 1940), although regular and timely decoding was not possible until the end of the year. (We have noted different assessments as to how useful Ultra was during the Battle of Britain.) Working with uncoded German radio messages also provided valuable information. This provided valuable intercepts with infornmation on force strength and targetting was available to the RAF. Dechipering Naval messages proved more challenging. The Kriegsmarina Enigma msachines were also cracked, but was more difficult because their operators were more careful to follow procedures and a fourth rotar was eventually added. The Royal Navy managed to obtain an intact Enigma machine and associated material needed to set the machines. Cracking the Kriegsmarina Enigma msachines played a major role in the defeat of the U-boat campaign in the North Atlantic.
The code name for the British effort to crack the German military Enigma cipher machines was called Ultra. It was one of the most closely guarded secrets of the War. It was conducted at a country estate called Blechley Park. It was an enormous task given the mathematical Complexity of the messages generated by Enigma.
The Ploes before the war were the first to crack the Enigma Machine. The Poles had first concluded that the Germans had began using a meanical cypher machine (1926-28). They began working on efforts to crack it and learned that it was based on a machine first developed by the German Railways. After the French Secret Service obtained operating manuals and old codes, the Poles sucessfully cracked into Enigma (1932). The Poles were able to read messages because the codes used for them were not changed regularly. The Germans would use the same codes fior several months. In the run up to the War, however, the Wehrmacht instituded revised signals procedures, including daily code changes. This put the Poles in the dark. This left the Poles with a possible 150 million settings to contend with on a daily basis. The Poles contacted the British and explained what they had done and the problems now experienced (Juky 1939).
The German Enigma machines were a vital component of Blitzkrieg. The German military used them for radio communications. Effective German communications were needed for modern mobil warfare. The effictiveness of Enigma was part of the reason for the victories in Poland and France. The French General Staff for example was still using messengers to communications. While effective, the use of messages sent by radio meant that German military communications were vulnerable. The German relying on their preceived notions of supperiority were convinced that their Enigma cipher machine could not be ceacked. And the Germans would not learn of the Allied success until well after the War.
Bletchely Park was an undestinguishe manor house. It became the site of the legendary secret British codebreaking activities during Workd War II and the first important use of early computers. Sir Hugh Sinclair, the Director of Naval Intelligence and the founder of the Government Code and Cypher School (GCCS) seeing that war was eminent used his own funds to purchase the Bletchley Park estate (1938). As war approached, the GCCS facility in London was evacuated to Bletchely (August 1939), At the same time, GCCS was the recepient of an envaluable and totaly unexpected gift from Polish intellgence--a Polish-built Enigma machine. Bletchley Park was located just outside Bletchley, a small country town 40 miles north of London and thus not a potential bombing target. It was at the junction of a main railway route to the north and the cross-country line linking Cambridge and Oxford Universities where much of the key staff was recruited.
The GCCS staff at first occupied rooms in the Mansion, but huts had to built on the grounds to handel the rapidly expanding code breaking effort. Their primary task was to intercept and decipher coded radio messages sent by the Germans using the Enima machine, but as time permitted they also worked on other Axis transmissiins (Italy and Japan) and transmissions of neutral countries. The heart of Bletchly Park became Hut 8 where Alan Turing and a group of other remarkable individuals using 'cribbs' begn to paintstakingly unravel the Enigma secret.
The British before the War and durung the first year of the war worked closely with the French. After the fall of France this coopration ended, but ties were not broken. The French effort with a few Poles continued at a low level in the Vichy unoccupied zone. When the Germans occupied Vichy, the French codebreakers dispersed some espaced to Algeria. The Germans managed to capture some, but were at first not aware of who they had. Late in the War, using torture, the Germans managed to extract some details of Ultra, butnot by anu means the full story.
All three German Wehrmacht servives (Heer, Kriegsmarine, and Luftwaffe) adopted the Enigma machine. But once adopted each services modified the machines and adopted varying procedures and codes for the machines. British code breakers at Bletchley Park faced different problems with the Wehrmacht, Luftwaffe, and Kriegsmarine codes. So the Bletchely Park codebreakers in essence had to crack three different, but related machines. And ech Service had several different keys which further complicated the code breaking effort. While this created complications, it also meant that because the machines were related, advances on one of the service Enigma machines were often helpful in cracking the other service machines. The easiest keys to break were those of the Luftwaffe, notiriously lax with security measures. The most difficult challenge was the Kriegsmaine Shark key used by Admiral Dönitz to control his U-boats in the North Atlantic.
The Bletchely Park effort achieved its first major success with the Heer (Army) Enigma machines (January 20, 1940).
Dilly Knox's team including two brilliant mathematicians, John Jeffreys and Alan Turing, suceeded in working out the Heer's administrative key which the named "The Green".
Dechipering Naval messages proved more challenging. After surviving the Battle of Britain (September 1940), the Kriegsmarine codes took on greater urgency, primarily but not only because of the U-boat campaign in the North Atlantic. The Kriegsmarina Enigma machines were also cracked, but was more difficult because Dönietz insisted that operators carefully folow security procedure. Bletchely Parks' work was aided by Royal Navy actions at sea. The Royal Navy minesweeper HMC Gleaner on patrol off Scotland happened upon U-33 laying mines (February 12, 1940). The U-boat was defensless as its torpedoes tubes were loaded with mines. After enduring depth charge runs, the U 33erupted at the surface, but befor making a run was hammered by surface fire. The U-boat lieutenant during the depth charge runs removed the eight rotors from the U-boat's Enigma and instructed the men he gave them to drop them overboard if they had to surface. In the choas tht followed, one of the men forgot to drop the rotors overboard. As a result, rotors VI and VII (the two which had wiring unknown to the Btitish) exclusively used by the Kreigsmarine reached Bletchely Park. [Budinsky, pp. 150-151.] The effort was given another major assist when the Royal Navy captured the German armed trawler Krebs off Norway (March 1941). The boarding party found the Enigma machines in tact along with associated codes. Admiral Döntiz had growing security concerns and as a result, a four rotar naval Enigma was developed. This sounds not all that important, but mathamatically in greatly increased the complexity of the transmissions. The introduction of the more complex Enigma cypher put the Allies in the dark at a critical time of the Battle of the Atlantic (early-1942). Turing was joined by Hugh Alexander, a British chess grandmaster and others to attack the naval Enigma messages. Alexander became one of the most important Bletchley code breakers. [Smith] The Royal Navy again managed to obtain an intact Enigma machine and associated material needed to set the machines. It took several months, but Bletchley Park finally broke back into the four rotor naval Enigma messages (late-1942). This set up the final phase of the campaigmn against the U-boats (early-1943). Cracking the Kriegsmarina Enigma machines would play a major role in the defeat of the U-boat campaign in the North Atlantic.
After breaking into the Heer 'Green' key, thev Bletchely Park code breakers next suceeded in cracking the 'Red' Enigma keys being used by the used by the Luftwaffe liaison officers coordinating air support for Heer units.
Bletchley Park for a time lost the critical Red cypher. A student named John Herivel developed a system that helped break back in (May 1940). [Smith] This meant that the Bletchely code breakers could support the RAF in the Battle for Britain.
The Luftwaffe code proved the easiest to crack, primarily because flushed with sucess, the Luftwaffe was the most careless about following established security procedures. Many messages were read because operators did not follow the established procedures. And of course because the Lufwaffe launched the the Battle of Britain (Juky 1940), the Luftwaffe codes were of great priority. The British suceeded in dechipering some Luftwaffe messages (May 1940), although regular and timely decoding was not possible until the end of the year. (We have noted different assessments as to how useful Ultra was during the Battle of Britain.) Working with uncoded German radio messages also provided valuable information. This provided valuable intercepts with infornmation on force strength and targetting was available to the RAF.
The German Railway System also had Enigma machines as did the SS. The German Railway System of course had originated the Enigma machine (1920s). By the time of World War II they had the upgraded military Enigmas. The Railway Enigmas provided useful inteligence. Bletchly Park had worked out that the Germans had decided to invade the Sovietv Union using Railway decrypts (March 1941).
Not all German military messages were sent by Enigma machines. There were several lower level German codes. Of these the most useful and chilling proved to be the German police codes.
Bletchly Park had begun working on German police ciphers (1939). The effort was directed by John Titman. The principal German police force was the Order Police. This included municipal and local police, firemen, and gendarmerie. Since tge NAZIs seized power, the moved to cntralize the police which during the Weimar Republic was primarily a number of different state and municipal forces under no central control. There was also a few para-military batalions established during the early years of the Weimar republic to confront political party para-military groups. This also served as aay of evading Versailles Treaty restructions on the Army. This was not a high priority operation, but Bletchly codebreakers felt that some useful kinfiormstion might turn up, if nothing else, clues as to morale and dissent. The effort was also considered good training as both the Army and Airforce used ciphers for medium-grade messages. It was a complicated effort because there was such a large volume of traffic, many different frquencies and from a large number of locations. The hand cioher system, however, was easily broken. The problem was obtaining intercepts, espoecially sfter the fall of France (June 1940). The Bletchly cryptologists were stunned after Hitker launched Barbstossa, the invasion of the Soviet Union (June 1941). They began decrypting messages about killing Jews, primarily reports of the number of Jewd being killed. This was not what the British had expected to learn from the police messages. The police units were apparently filling these reports to establish their achievements. Similsr reports appeared from the SS Orange Enigma decrypts. So many of these reports came in that Bletchly had to enquire if they should continue to submit them. The Foreign Offive asked that detailed records be kept for procecutions after the War. As it turned out, there was so much information available to the procecutoirs after the Wat, thst the poliuce decrypts were not needed. [Budiansky, pp. 196-202.]
The Germans provided their Italian Allies Enigma machines because Italian units were fighting with the Germans in North Africa and the Eastern Front. The Italians used German provided Enigmas during the Spanish American War and after they entered World War II. The Enigmas the Italians used did not have many of the compications added to the German machines over time. As a result they provedrelatively easy to crack. In fact the first tactical victory from an Enigma decrypt came from an Italian message ans led to the Royal Navy victory in Battle of Cape Matapan (March 1941).
The Finns, Hungarians, and Romanians were also fighting on the Eastrern Front, but we are not yet sure if they were provided with Enima Macgines. The Japanese had their own code systems.
Ultra proved to be one of many beneficiaries of the Anglo-American alliance. The British codebreakers in Bletchely Park began breaking into German Enigma cyphers (April 1940) and slowly increased their initial penetration. Churchill became primeminister (May 1940). He had been secretly corresponding with the President. Churchill at very early point decided to marry the British war effort with the Americans at a time the United States was still neutral.
He decided to make the resulting Ultra intelligence available to the President through the British Security Coordination (BSC) unit and Federal Bureau of Investigation (FBI). William Stephenson who headed the BSC was authorized to view raw Ultra transcripts. Churchill allowed him to decide what Ultra information to pass along to the President. We are not sure yet about just what was provided or to what extent the source of the information was made clear at this early point. He soon went much further. He ordered British secret technology be fully shared with the Americans. This included Ultra.
As the War progressed, the Americans largely took over the effort to crack Japanse codes, an effort which they called Magic. The British shared the Ultra secret with them. This was the beginning of the very elaborate and close cooperation between Britiish and American codebreakers. American resources would play an impportant role in the Ultra effot. American codebreakers subseuently cracked the Japanese diplomatic Purple machine Magic inteligence (September 1940). The President authorized sharing the results with the British. British codebreakers would then work with the Americans on the Jpanese naval code--JN 25. The Blethley Park code breakers were reluctant to share too much with the Americans, in part seeing them as not sufficently security concious. Irionically it was tghe Briyish who committed the greatest Allied security failure of the War, not recognizing that Naval Cipher No. 3 had been broken. The British had oerformed wonders with the early cracking of Enigma with intuitive insights and Turings theoretical leaps. But as the Germans introduced further complications and as the number of messages interceoted increased, it was the Americans who stepped in by producing calculators (bombes) in large numbers and important refinements. This provided the brute force for rapid key solutions and decyphering huge numbers of messages.
Cracking Wehrmacht Enigma transmissions was only part of the Ultra story. Next the Bletchely Park team had to woek out a system of making sence out if the mass of messages that they began to read and then getting tghe information to the people who could best put the information to the best use. And this had to be done while at the samne time mainting the secret that they had cracked the Enigma machines. Bletchely Park began profucing decrypts, in fact significant numbers of decrypts, before a system had been created for analyzing and desimanting the decrypts. This is not surprising given the fact that it was not at all certain when the effort began that it was possible to crack Enigma and even if cracked producing decrypts in any number and in a usable time frame. Gordon Welchman, a mathematical genius, began this phase of the operation. He would head of the Army and Air Force section and devised a system to aid the Bletchely Park code breakers with Army and RAF officers. This group in a nearby Hut Six were given the job of turning decrypts into usable intelligence reports. Welchman played a huge role in the sucess of Ultra, but is less well known than Turing, a colleague since university. It was Welchman who adapted Turing's Bombe designs to create the indespensible device for decrypting the German transmissions. His devise
became known as the 'diagonal board'. Welchman set up Hut Six and oversaw its operation. They would decrypt more than one million German messages during the War. [Greenburg]
Ultra had a significant impact on several major military campaigns. The Bletchely Park codebreakers began to crack Enigma codes at a very early point of the War (January 1940) and additional progress followed rapidly after that. Developing systems to evaluate and interpret the decrypts and then to deseminate actionable inteligence to military commands. As a result, although Bletchely Park was developed detailed information on the German Western offensive (May 1940), systems were not in place to get useful information to field units nor were field commands ready to accept the accuracy of the information provided, in part because the source was obscured by passing it off as MI6 espionage. Some commanders were afraid that it might be enemy disinformation. This gradually changed as commanders learned how accurate and reliable the ingormation was. The Ultra decrypts would have a major impact on the North African campaign. The greatest problem proved to be the naval Enigmas, but ultumately this proved to be some of the most valuable information. Ultra had a major role in preparing for D-Day. The greatest failure was the German Bulge offensive, but the failure here was more of command failure to use Ulta than the Blethley Park code breakers as well as German signals discipline.
The Bletchely Park code breakers were the first to learn of the mass killing of Jews in the wake of Barbarossa (June 1941). The Einstatzgruppen units (SS paramilitary death squads), anxious to inform Berlin of their achievements began sending messages whichg included body counts of the Jews they were killing. Even at this early stage, the messages indicated the horrendous news that the Germans were murdering ten of thousands of Jewish civilians. They informed the Primeminister. Churchill went ffurther in this instance in risking the Ultra secret. He announced that the Germans were killing civilians in large numbers, alling it "a crime without a name". He ordered Bletchely Park to detail a specialist to collect evidence from decrypts for use as evidence in the war crimes trials after the War. This was not possible because Ultra was kept secret after the War when the International Military Tribunals were held. The Germans certainly heard Churchill's broadcasts. Einstatzgruppen were discouraged from reporting their killing electronically, but of course not from pursuing their murderous rampage.
Enigma was not the only German code system with which the Allies had to conted. The German High Command (OKW) asked the Lorenz company to build a high security teleprinter cipher machine to give them the ability to send and receive radio messages in absolute secrecy. This was a system even more secure than the Enigma machines. The Lorenz company came up with a cipher machine based on the additive method for enciphering teleprinter messages. The system has been invented by Gilbert Vernam in America (1918). Teleprinters are not based on the standard 26-letter English alphabet (which is very similar to the German alphabet) and Morse code on which the Enigma machines are based. Rather teleprinters use the 32-symbol Baudot code. This consists of five channels each of which is a stream of bits which can be represented variously as no-hole or hole, 0 or 1, dot or cross. The Lorenz code presented an order of complexity above that of the standard Enigma system.
OKW beginning in 1942 used the Lorenz system to communicat with senior Army Group commanders meany very important messages. The British codenamed thevLorenz Cipher system Tunny. By this time the Bletchhly Park was developing Colossus, a proto-electronic digital computer. The British using Colossus by 1943 were decryting Tunny messages in quantity. Colossus enabled them to decrypt the messages faster than the Germans and in real time.
Cambridge graduate John Cairncross worked at Bletchley Parrk (1942-43). He is believed to have joined the Communist Party (1943). At Bletchley he worked on Ultra ciphers. The definitive history on his activities has not yet been written, but some infirmation is known. Cairncross is known to have secretly passed raw decrypts to the Soviet Union. His Soviet code name was Liszt because he loved classicl music. His NKVD handler ordered him to get into Bletchley Park (called Kurort by the Soviets). The process at Bletchly Park was to pass the raw decrypts to intelligence officers who created reports based on this material and disguising its origin. The raw decrypts were then destroyed.m Cairncross was able to smuggle raw Tunny decrypts designated for destruction out of Hut 3. He hid them in his trousers, transferring them to his bag at the railway station. He then turned then over to his NKVD contact in London. The decrypts made it clear to the Soviets tht thev Brutish had cracked German codes. As far as we know, the Soviets while they got the decrypta dis not gt detils on how the codes were being broken. At the time, the Allies were pasing some of tge reports to the Soviets. The wary Stalin, however did not trust such reports unless he knew the sources. The material passed to the Soviets by the allies as well as the decrypts from Caircross provided the Soviets a great deal of detailed information on Operation Citadel which is part of the reason tht the Red rmywas so preapred for the Bttke if Kursk (July 1943). [Copeland, pp. 1-6.] There are rumors that MI-6 knew of Cairncross, as saw it as beneficial to pass the raw Colossus decrypts to the Soviets. We know of no real evidebce of this. Caircross is believed to be the Fifth Man in the Cambridge Soy Ring, but he appears to have worked independently of Philby, Burgess, and the others.
Budiansky, Stephen. Battle of Wits: The Complete Story of Codebreaking in World War II (Simon and Schuster--Touchstone: New York, 2002), 436p.
Copeland, Jack. "Introduction" in Colossus The Secrets of Bletchley Park's Codebreaking Computers. Oxford University Press: 2010).
Greenberg, Joel. Gordon Welchman: Bletchley Park's Architect of Ultra Intelligence.
Smith, Michael. Station X: The Code Breakers of Bletchley Park.
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