Enigma History |

1918 |

Invention of the Enigma |

The history of the Enigma starts as early as 1918, when the German Arthur Scherbius filed his first patent for the Enigma coding machine. The image below shows a drawing from patent number 416219 as found in the archives of the German Reichspatentamt (patent office). Please note the time at which the Enigma was invented: 1918, just after the First World War, more then 20 years before WWII!
The image clearly shows the coding wheels (rotors) in the center part of the drawing. Below it is the keyboard and to the right is the lamp panel. At the top left is a counter, used to count the number of letters entered on the keyboard. This counter can still be found on certain Enigma models. Arthur Scherbius' company Securitas was based in Berlin (Germany) and had an office in Amsterdam (The Netherlands). As he wanted to protect his invention outside Germany, he also registered his patent in the USA (1922), Great Britain (1923) and France (1923).

The commercial Enigma |

Between 1920 and 1925 the Enigma was available as a commercial device, available for use by companies and embassies for their confidential messages. Remember that in those days, most companies had to use morse code and radio links for long distance traffic. This image shows an advert for a commercial Enigma machine in the period between 1920 and 1925. The image clearly shows the keyboard, the lamp panel and the coding wheels. Please note that this version had no Stecker board as compared to the later models used by the German army. The devices were advertised having over 800.000 possibilities. |  |

Who invented the Enigma? |

It's a common misconception that the Enigma was initially invented by the Dutchman Hugo Koch. This is probably due to the fact that Arthur Scherbius later bought Koch's patent rights in order to consolidate his own patent rights. Although both patents share some similarities, the Scherbius patent was registered first in 1918, whilst Koch's patent is dated 1919.

1926 |

The German Army buys the Enigma rights |

Initially, the German Army wasn't interested in Arthur Scherbius' invention and the Enigma had only a limited success as a commercial device. However, in 1926, with advanced plans for another war, security advisors managed to convice their superiors that this would be an ideal device to keep their radio messages secret.

Subsequently, the German Army bought the rights to the Enigma patents and the device remained commercially available until 1932. In order to improve security, the German Army made some important modifications to the Enigma. First of all, they changed the wiring of the wheels so that it would be unknown to an outside party. They also changed the Enigma setup procedure. This is the rather complex series of actions involved to prepair the Enigma for use. But the most important change of all is probably the addition of a plugboard enabling the operator to swap any pair of letters. As the German word for 'Plug' is 'Stecker', this is often referred to as the Stecker board, or Steckerbrett. If no patch cable is present, there will be no swapping. If a cable was connected between, say, the E and G, this would mean that E would be translated into a G and G would be translated into E. As there are 26 letters in the alphabet, a maximum of 13 cables could be used. However, mathematics show that the maximum number of permutations is achieved when using 11 cables. The Steckerbrett added greatly to the complexity of the Engima, especially since any number of cables could be used, from none to 11 (or 13). It would multiply the number of possible combinations by: 532,985,208,200,000! |  |

1928 |

The Poles are interested |

In 1928 the Polish secret service became interested in German radio traffic as they saw the danger of yet another war just around the corner. The German Army already transmitted most of its radio messages in enciphered form, and the Poles wanted to know what this was all about.

1932 |

The British are interested |

In 1932, British intelligence takes an interest in the German coded messages. One of their key militairy experts, Dylwyn Knox sets out to break the Enigma codes, but without success. However, due the the increasing number of radio messages sent by the Germans each day, a new form of intelligence is developed: Radio Intelligence. Despite the fact that they were unable to read the messages, the number of transmissions and the average location from which they were sent, gave them valuable strategic information. There are hardly any pictures of Dilwyn Knox left and this is the only one I could find. Click the image to read the credits by the GCHQ. |  |
Dilwyn Knox

1933 |

The Poles break the Enigma |

As stated before, the Poles were the fist to recognise the danger of another German invasion and started to work on German ciphers in 1928. In 1932 they recruted three young billiant mathematics students of the University of Poznan: Marian Rejewski, Jerzy Rozycki and Henryk Zygalski. They began to work on the simpler German Naval codes first, until Rejewski was given a separate room and told to work on Enigma traffic. In the beginning of January 1933, Rejewski first broke the Enigma codes. Based on a combination of mathematics, statistics, computational ability and inspired guesswork. He managed to deduct the full wiring details of each wheel and also derminded the interdependance between the various parts of the Enigma, inluding the Steckerbrett. This enabled the Poles to produce replicas of the Enigma that were used to decode the German messages. Some time before, the Polish Intelligence Agency obtained the Enigma setup procedure from a French Secret Agent. From this moment on, the Poles were able to read most of the German radio traffic. |  |
Marian Rejewski

1934 |

Hitler becomes self-proclaimed Führer |

The breakthrough by the Polish cryptographers came right on time as a few weeks later, 30 January 1933 to be exact, Hitler became in power as the new Reichs Chancellor of Germany. One year later, after the death of President Von Hindenburg, Hitler became the new self-proclamed Führer. Check out this biography of Hitler |  |
Adolf Hitler

1938 |

The Poles keep breaking the Enigma |

From the first breakthrough in January 1933, the Polish cryptographers could read almost all German Enigma radio traffic. In the period between 1934 and 1938 they noticed an enormous increase in radio traffic as Germany prepared to go to war again. In March 1938 the German Army invaded and took over Austria, which then became part of the German Reich, the so called Anschluß. The Poles, capable of reading most of the German Enigma messages, must have felt the increasing thread of a full scale war. During this period, the German Army changed the Enigma again, by introducing a new radio procedure and two new wheels in addition to the existing three wheels. However, at this stage, the Germans only changed the Enigma settings once every month. In order to speed up the breaking of Enigma messages, the Polish cryptographers constructed an electro-mechanical machine, called the Bomba.

1939 |

The Poles give away their secrets |

By mid 1939, the threat of an invasion reaches its peak and on 24 July, the Poles invite the British and French Intelligence Services to Pyry, near Warsaw. At this meeting, the Polish cryptographers share their knowledge with their foreign counterparts and hand over some Enigma Replicas. For the British, this was a great help which would save them some two to three years of research. At 1 September 1939, Germany invaded Poland, which marks the beginning of WWII. During the meeting in Pyry, the Poles gave away two Enigma replicas. When Germany invaded Poland, 15 Polish cryptographers fled to France where they continued their work in the secret unit named Bruno. They ordered some more replicas to be made by French technicians. The image on the right shows one of these extra replicas, which is the only Polish replica known to have survived the war. The machine is held at the Sirkorski Insitute in London. Note that the Steckers are located above the wheels, rather than at the front of the machine, like on an original Enigma. |  |

Formation of Bletchley Park |

As the threat of war loomed, the British Government Code and Cypher School (GC&CS), based in London, was looking for a safer more quiet place to carry out its intelligence work. They would find a private estate, called Bletchley Park that was suitable for their purposes. Bletchley would probably be safe in case of bomb raids and it had good road and train connections to London, The North, Cambridge and Oxford. In August of 1939, just a week before Poland was invaded by the Germans, The first codebreakers arrived at Bletchley Park. In order to hide their true identity, they masqueraded as Captain Ridley's Shooting Party. Initially, a team of some 50 cryptographers started work at Bletchley Park. Among them, the now famous British mathematician Alan Turing. |  |
Bletchley Park today

England is at war |

On 3 September, two days after the invasion of Poland, both France and Great Britain declare war to Germany. At the start of the war, the Germans again changed the Enigma setup procedure and from then on, they would change the Enigma settings on a daily basis. In order to cope with the increasing number of radio messages, many listening stations, the so called Y-Stations or intercepts stations were setup along the coast line. They were operated by radio hams, but also house wifes who were given an intensive training in reading morse code signals. Many house wifes were so good at this, that they could sometimes recognise the 'morse handwriting' of the German operator at the other end. |  |

Codename ULTRA |

The whole operation at Bletchley Park was so secret, that it was only known to those who actually needed to know it. As it was even more secret then Top Secret, they codenamed it ULTRA. The importance of the Ultra Intelligence and the influence it had on the outcome of the war, has only become known in recent years. An still today, not all fact are out in the open...

1940 |

First successes at Bletchley Park |

In the beginning of 1940, Alan Turing achieves his first breakthrough in breaking Enigma messages. More and more people are recruted to work at Blethley Park to handle the enormous amount of messages each day. In order to speed up the breaking of Enigma traffic, Turing constructed his own variant of the Polish Bomba, called the Bombe. During this period, Germany invaded Norway and France. At the same time, they introduced three more wheels to the Enigma, giving a total of eight wheels. As each Enigma has three movable wheels, any three out the total of eight could be used, in any order. This would greatly increase the maximum number of permutations! But that's not all. They soon discovered that the Enigma setup procedures used by the German Navy (Marine) was far more complex that the procedure used by other departments of the army (Wehrmacht and Luftwaffe). Furthermore the Navy used codebooks for almost anything, even the weather report. Despite an occasional break of Naval traffic, the messages sent to and from the U-boats were completely unbreakable. This would keep the cryptographers at Bletchley Park puzzled for a long time to come. |  |
Alan Turing

Traitise on Enigma |

In 1940, Alan Turing starts to write his Treatise on Enigma, a paper describing the ins and outs of the Enigma, both mechanically and mathematically. This paper has been unknown until its release by the NSA (National Security Agency) of the United States Government in April 1996. Turing must have written this document, sitting in a small room of The Cottage (see picture) at Bletchley Park. At present, the full document of the Treatise on Enigma is held by the PRO (Public Record Office) and is Crown Copyright. However, you may download parts of it for private use, directly from the PRO website (see below). Click here to see the first page of the original document Read the (partly) retyped and reworked document Andrew Hodges' analysis of the Treatise |  |
The Cottage

1941 |

The Capture of U-110 |

Apart from writing his Treatise on Enigma, Turings spent most of his time in 1940 and 1941 on the Naval U-boat cyphers. All this time, the U-boat Enigma messages remained unbreakable. All that changed with the capture of the German U-boat U-110 on 9 May 1941 by the British HMS Bulldog. The U-boat was attacked with depth charges and was forced to the surface. The captain ordered his men to abandon ship, assuming that the boat was bound to sink... However, the U-boat remained afloat, and the crew of the Bulldog managed to recover an Enigma and some secret documents, which later turned out to be code books. |  |
The U-110 being towed away

This image shows one of the German code books, the so called Kurzsignalheft 1941. The code books were printed with special ink that would dissolve in water. The sinking of a U-boat would be enough to make the code books unusable. As the allies now had a code book, they had a clue as to what the contents of a message could be. Breaking the U-boat codes was important as the U-boats sank many supply ships traveling from the USA to the UK every day. There were times when 140 supply ships would set for the UK, whilst 120 of them were sunk by German U-boats. This part of the war is often refered to as The Battle of the Atlantic. |  |
Kurzsignalheft

Breaking the daily Enigma keys would still be difficult, as they would have to recover the settings for Walzenlage (wheel order), Ringstellung (ring settings), Steckerverbindungen (patch cables), Grundstellung (initial position), etc. The image below shows part of a page from a code book containing the settings for a 3-wheel Enigma (not used for the U-boats).
As you can see, the settings were changed each day. As the columns for Ringstellung show numbers rather than letters, we may assume that this was meant for a Heeres Enigma, used by either the Luftwaffe or the Wehrmacht.

Breakthrough in Naval M4 Enigma traffic |

With the capture of the U-110, Bletchley Park was no longer in the dark. They now knew that the U-boat Enigma had four rotors, rather than three as on the other models. Furthermore, they now had the complete wiring of all wheels and they had, of course, the short message code book. This lead to the breaking of the M4 keys on a daily basis for quite some time to come. As they managed to keep the capture of the U-110 secret, the Germans didn't have a clue and therefore didn't change the Enigma procedures. This period must have been one of the most critical ones of the war as it had great influence on the outcome of the war. It is now believed that it shortened the war by some 2 years. In addition to the broken Enigma messages, a new and advance method of radio direction finding was deviced. This is known as HFDF or HufDuf, which stands for 'High Frequency Direction Finding'. U-boats could receive messages, transmitted on long-wave frequencies, under water. But if they wanted to answer a message, using short-wave frequencies, they would have to surface, as short-wave frequencies cannot be used under water. With the HFDF method it was possible to determine the position of a U-boat in just a few seconds. |  |
A 4-wheel Enigma M4

Action this day |

In October 1941, Churchill pays Bletchley Park a visit and recognises the importance of the work carried out there. By this time the workload at Bletchley Park is enormous. There are too many messages every day and they are short of money, supplies and most of all staff. On 21 October 1941, four of the leading codebreakers (Alan Turing, Gordon Welchman, Hugh Alexander and Stuart Milner-Barry) wrote a confidential letter directly to Churchill. For months they had been trying to get their requirements through the normal channels, but to no avail. Hence the reason to write the Prime Minister directly. Churchill, impressed by the letter and conviced of the neccesity of the work carried out at Bletchley Park, responds the next day with a letter, labelled 'Action this day', to General Ismay with the following contents:

`Secret In a box Gen. Ismay Make sure they have all they want on extreme priority and report to me that this has been done. WSC`

1944 |

Activity at Bletchley Park |

Exactly how many man and woman worked at Bletchley Park during its peak, is unknown. There are guesses between 1,000 and 10,000 people, the latter probably being more acurate as it's the figure given by the GCHQ. At some point in 1944, 7000 man and woman worked there in 4 shifts, every day and night to handle the enormous amount of radio messages: many thousands each day! People worked in huts (small wooden buildings) and they didn't know what went on in the other huts. They were allowed to socialise with other employees, but they could never talk about work. Which, of course, they didn't. |  |

1945 |

Hitler commits suicide |

The U-boat section of the German Navy was headed by their commander Karl Dönitz. Dönitz was a stubborn man, and despite the fact that he lost many U-boats, he never doubted the security of the Enigma. At some point his advisers asked the German Abwehr (Intelligence Agency) to check the security of the Enigma, but cryptographic experts assured them that it was impossible to break. On 30 April 1945 he sent the following message to his crews around the globe: |  |

`HRQN SMAD LVIO DMMW JLKN GSRJ VNLC IKGT MDRB IDAW YLIK IFIF CMCG HRQN SMAD`

Decrypted with the Enigma settings for that day, it reads the following: Der Führer ist tod. Der Kampf geht weiter, Dönitz.

Britain's Best Kept Secret |

Despite the fact that some parts of the German army still wanted to continue their battle, Hitler's death more or less marked the biginning of the end. Shortly after his suicide, the war would be over and the allies would be in charge again. Winston Churchill, always a great fan of the Ultra Intelligence work, visited Bletchley Park shortly after the war was over, and asked for confidentiality. As he didn't want anyone to know anything about what happened here, he instructed all evidence to be destroyed. Machines were dismantled and most paperwork was burned on site. And for may years this would remain Britain's Best Kept Secret. It is rumoured that a significant number of captured Enigma machines was subsequently sold or given to foreign nations, who could use it for their own confidential radio traffic, e.g. between embassies. Enigma machines have been used at least by Norway, Switserland, Argentina and The Netherlands until the 1960's. |  |

1946 |

The Cold War |

The end of the Second World War, also marks the beginning of the Cold War. It was of vital importance that the former ally, the USSR, would never find out about the Bletchley Park wartime achievements. By March 1946 they were all gone. Every scrap of 'incriminating' evidence was destroyed, just like Churchill had orderd. With respect to the codebreakers and their ultra secret work, Churchill once called them: The geese that laid the golden eggs and never cackled. Most people went off to other jobs or back to their studies. Some continued their codebreaking efforts under a new name: the Government Communications Headquarters (GCHQ). Turing moved to Manchester University were he worked on the British computer initiative. He also remained active for the GCHQ. Bletchley Park remained in use by the Post Office and GCHQ as a training centre for teachers, Post Office workers, air traffic control system engineers and members of GCHQ. |  |
The Manchester Computer

1952 |

Alan Turing arrested |

Being an openly gay man, Alan Turing, was considered a security risk. In 1952, he was arrested and put on trial. In order to avoid going to prison, he had to take hormone treatment, which they believed would cure him. He lost his security clearance and found himself under watch. Eventually, he took his own life in 1954 by ating an apple dipped in cyanide. Read all about it on the Turing home page

1974 |

Winterbotham's book: The Ultra Secret |

The full story about the Enigma and the breaking of its codes, whas kept secret for many years, just like Churchil had instructed. The first publication that really came as a shock to many people was the book The Ultra Secret by Winterbotham. This was the first time anyone outside Ultra would learn anything about the allied codebreaking efforts. Winterbotham wrote the book from memory, as he had no access to the classified information of those days. His book therefore contained some minor inacuracies and errors, but it gives a good insight as to what happened during WWII. The book caused great upset with the British authorities, but gradually more and more would be reveiled in the following years. It also triggered other former codebreakers to tell their story or write a book themselves.

1979 |

Enigma, by Wladyslaw Kozaczuk |

In 1979, the Polish Wladyslaw Kozaczuk wrote a rather complete book describing the wartime effort of the Polish Cryptographers in the time before and during WWII. Unfortunately the book was written in Polish thereby making the information unavailable for most researchers on the subject. In 1984, the book was translated and republished, this time in English. For a long time, there were doubts about the importance of the Polish contribution to the breaking of the Enigma, but recent discoveries in both British and American archives, have revealed credible evidence that the dicoveries of the Poles were of vital importance.

1982 |

The Hut 6 Story, by Gordon Welchman |

In 1982, Gordon Welchman, one of the original British cryptographers who headed Hut 6 for a substantial period, put his memories on paper and released his book: The Hut 6 Story. Despite the fact that this publication came 8 years after Winterbotham's book 'The Ultra Secret', it again caused a great shock and eventually Welchman lost his security clearance in the USA where he had been living since the war. The Hut 6 story is a very readable book, describing the early days at Bletchley Park before the war, the formation of Hut 6, the first breaking achievements and the building of the Bombes. It also gives some in-depth details about how the codes were broken and what kind of mistakes the Germans made to compromise the Enigma's security.

1991 |

Bletchley Park facing demolition |

In the years following WWII, Bletchley Park was used by the GC&CS (now called GCHQ) and the Post Office (now called British Telecom) as a training center. Extra buildings were erected and the old wartime huts were left abandoned. After some 50 years of association with British Intelligence, Bletchley Park was finially decommissioned in 1987. By 1991, Bletchley Park was almost completely deserted and plans were made for demolition of the existing buildings to make way for housing development. A farewell party was held on the grounds and over 400 former codebreakers were present. |  |

The Mansion
Hut 6
Close-up of Hut 6

Despite the fact that The Mansion was kept well preserved, most of the former huts were in a pretty bad state. In the centre image the remains of the surrounding anti-bomb wall, can still be seen.

Present time |

The Bletchley Park Museum |

In February 1992, the Milton Keynes Borough Council, declared most of Bletchley Park a conservation area and The Bletchley Park Trust was formed only three days later. They started negotiations with the landowners and first opened the site to visitors in 1993. Finally, in July 1994, Bletchley Park was officially opened as a museum. Today, Bletchley Park is a modern museum showing many aspects of the Enigma and codebreaking in general. They have a nice collection of Enigma machines, but also a working replica of the Bombe. The full story of codebreaking can be seen here, from the transmission of German messages in the field, through the intercepts stations, to Bletchley Park and finally to the decision makers. But there's more. The very rare Lorenz Geheimschreiber (used by Hitler for extremely secret messages) is on display and the first computer ever: Colossus (used to break the Lorenz cipher) is being rebuild here. More and more of the old huts are being restored and new exhibitions are added every now and then. |  |
The Mansion at Bletchley Park

Conclusion |

You might wonder why a post-war person, like me, is so interested in the technology used during WWII. I have to admit, I've asked myself this a number of times. First of all, WWII is an important period in modern history as far as technology is concerned. Never before or after the war have so many things be invented and developed as during those four years. Things that we now take for granted, such as laser, radar or computers were all invented or further developed during the war. The Enigma in particular, is a very cunning device. It's surrounded by secrecy and romantic and the story of it's breaking has only been reveiled in recent years. As the war is now about 60 years old, more and more formerly secret documents are now being released by the various Intelligence Agencies. So, despite the fact that all of this happened such a long time ago, it's still possible for us to discover new facts. Paul Reuvers, October 2003.

© Copyright Paul Reuvers. Last changed: Thu,16 Oct 2003.17:44:33