World War 2 was the first war to be fought with the use of computers. Both the Axis and the Allies employed them for use, some more effectively than others, but trial and error proved that modern warfare could not be fought without them. Computers did more than just plot the trajectories of projectiles or tell a submariner when to fire a torpedo. The computer played a vital role in winning the war in another way and with the anniversary of VE Day yesterday it is important to acknowledge this.

What was Enigma?

Wireless communications were used by both sides to communicate over vast distances. It allowed both side’s navies to be in contact with headquarters despite being thousands of miles away. Since communications were made over the airwaves the other side was able to listen in so encrypting these communications were imperative. The Germans were extremely secretive about their cipher machines, most famously the Enigma Machine, and the Lorenz cipher that it utilized.

Enigma used a series of electro-mechanical rotor ciphers to encode and decode both military and diplomatic communication. Both of Germany’s principal allies, the Italians and Japanese also used their own versions of these machines. Rotors (also called wheels or drums) were rotated to set the program for encryption. A user would hit a key on the keyboard and a corresponding character would light up on the lampboard thereby either deciphering the code or encrypting the code for later transmission via Morse Code. Enigma had been developed in the 1920s but was still in use in the 1940s and the German military model was the most complex version developed. French spies and Polish codebreakers had managed to build a copycat of the machine before the war and had managed to break Enigma. The Germans responded by adding two more rotors increasing the complexity of the code and proved too much for Polish codebreakers in the limited time that they had before Poland was invaded at the beginning of World War 2.

How did the English know about Enigma?

The Poles did build a new copy of the Enigma machine and handed it over to the British government shortly before Germany invaded in 1939. The Royal Navy was also able to obtain an authentic German model from U-110 in 1941 when HMS Bulldog captured the ship. The Kriegsmarine sailors were convinced that their boat was going to sink and simply abandoned it but it stayed afloat long enough for British sailors to snoop around and take anything that looked valuable. In a bit of luck the device was taken only because it looked out of place to the boarding party.

The Allies had the machines but needed to break the code and efforts to break the Enigma code became known as Project Ultra. Outside of the Manhattan Project was possibly the most tightly kept secret of the war. The codebreakers were set up at Bletchley Park outside of Milton Keynes with the objective of breaking the Lorenz cipher. There was some success reading German intercepts but it was slow work made more complicated when the Germans also began using a new device, the Lorenz Schlüsselzusatz (known to the British as Tunny or their slang for a tuna fish sandwich) teleprinter cipher machine but these devices worked along some of the same principles as Enigma. What little information was gleaned was used with decisive results like knowing the location of German U-Boats which helped to win the Battle of the Atlantic and prevent the starvation of the British Isles.

Why was Enigma so hard to break?

While codebreakers could read the messages Enigma and Tunny machines offered somewhere around 151,000,000,000,000 different combinations of the Lorenz cipher to test before a successful reading the message. One could imagine how long it would take to decrypt a message using each cipher and there was also no guarantee that the same cipher would be used for other messages as the Germans changed ciphers daily. British code breakers were having some success but it was not coming fast enough. Speed was essential as intelligence is only as good as the speed that it can be acted upon.

Only one thing offered the speed needed

There was only one option to break the Lorenz cipher, a computer and the War Government turned to Max Newman to lead the team that would build it. Newman had previously worked on a device designed to attack Tunny but that had proven ineffective against Enigma. Alan Turing, an engineer, brought in to help with the project and invented a method to produce tables for manual analysis known as rectangling. Tommy Flowers designed the machine with help from Harry Fensom, Allen Coombs, Sid Broadhurst and Bill Chandler at Dollis Hill. The project built on a previous effort called Heath Robinson that had difficulty working with the paper tapes that were used to feed in information. A new tape input method was devised that was capable of reading 1,000 to 2,000 characters per second and work began in February of 1943. Turing’s work played an important role in cracking the code and his work was aided by sloppy German radiomen which sped up decryption. It also helped that each message ended with Heil Hitler which helped to speed up decryption.

A prototype was complete by December of 1943 and shipped to Bletchley Park. It tried its first message on February 5, 1944. The prototype worked and four units were ordered in April, which increased to twelve by June. The first Mark II unit became operational on June 1 and was immediately used to procure intelligence to aid the Invasion of Normandy scheduled for a few days hence. These units had a tape transport system with an 8-photocell reading mechanism, twelve thyratron ring stores that simulated a Lorenz code machine, panels for input, five electronic counters and an electric typewriter. Paper tags with punched paper tapes were used and the Mark II could read 5,000 characters per second. It was operated by cryptanalysts from the Women’s Royal Naval Service with engineers on hand for maintenance. Ten of the machines were in use by the end of the war with an eleventh ordered.

The benefits (and pitfalls) of knowing what the enemy was doing

With the Lorenz cipher broken and the Allies able to read their enemy’s messages it made winning the war much easier but there were consequences. This was a Top Secret effort and while the British government knew the targets of German air raids they could not move resources to stop them. They deduced that the German High Command would figure out that the Lorenz cipher was broken and adapt nullifying their advantage. Several British cities like Coventry were leveled by the Luftwaffe when it could have been stopped or slowed. There were other far reaching consequences. The British government was well aware of what became known as the Holocaust but refused to release any information in the fear it would compromise Ultra. Whether releasing any information about the Holocaust would have saved any lives is doubtful though. MI5 often withheld information from Winston Churchill to prevent an accidental release and Churchill himself did not tell American President Franklin Roosevelt about the captured Enigma until the United States entered the war.

The fate of Ultra

Following the war all of the active machines were dismantled. Two units that were under construction were completed and retained for use with GCHQ but were also dismantled by 1960. They had been unable to be adapted to other purposes. Many of the people involved like Newman, Turing and Harry Huskey became pioneers in the computer field in Great Britain but were never able to speak about their work and thus never recognized until well after the fact. It seemed to some that computer geniuses simply emerged from nowhere after World War 2. That was until 1974 when RAF Group Captain Frederick Winterbotham wrote a book about Project Ultra and spilled the secret.

Rebuilding Ultra

In 1991 the idea of rebuilding Colossus was introduced by Tony Sale, a former MI5 computer engineer and co-founder of the Bletchley Park Museum. With little information to go on he began work in 1993 and had a functional model by 1996. One of the original team members, Tommy Flowers, was present when it was switched on. It took another eleven years to complete the project. A competition was staged at the museum pitting modern machines up against Colossus. Colossus was out of its class against modern technology but all involved were impressed by what a piece of 1943 World War 2-era technology could do. While there is no way to possibly quantify it, it is believed that it shortened the war by two years and may have saved as many as fourteen million lives.

The Enigma machine is one of the most famous pieces of technology to come from World War 2 but very few survived. Most were destroyed by retreating German soldiers or lost when a ship was sunk and it is believed that there are about 150 in existence today. In 2015 one was auctioned and sold to a private collector for $365,000. Another was sold in 2014 for $265,000.

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