At Bletchley Park, breaking Enigma codes and winning WW II

Road Trip 2011: Code breakers led by Alan Turing were able to beat the Germans at their cipher games, and in the process shorten the war by as much as two years. At Bletchley Park, all the work took place in secret, where it stayed for decades.

Daniel Terdiman Former Senior Writer / News
Daniel Terdiman is a senior writer at CNET News covering Twitter, Net culture, and everything in between.
Daniel Terdiman
4 min read

This is one of just a few surviving photographs of the original Colossus. Based on this and the few others, vintage computer experts and World War II historians have been able to recreate the Colossus machine that helped break the Enigma codes and win the war. Daniel Terdiman/CNET

BLETCHLEY, England--The list of important sites is endless: Omaha Beach, Dunkirk, London, Paris, Toulon. But if you're a real World War II aficionado, you may think of Bletchley Park with special fondness.

This nondescript town about 45 minutes outside London is where famed mathematician Alan Turing led a group of master code breakers in a successful battle against Germany and its once-unbreakable cipher codes.

Over the course of several years, the British government assembled a team and sequestered it here, working on various devices intended to break the codes. In the days prior to the war, the Germans rarely changed the code key for Enigma. But as the war developed, they changed it daily, and sometimes more than that. And that forced the code breakers to find a way to fight back and swiftly.

Breaking the Nazis' Enigma codes at Bletchley Park (photos)

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What that meant was big, sophisticated devices like what was known as the Bombe, which broke the Enigma codes andColossus, a machine that was purpose-built to take on the daily key changes made by the German high command and solve the codes they sent using a machine called the Lorenz.

The machines and the work done at Bletchley Park were so secret that not only could those who toiled there not talk about it during the war, but not afterward either. And it's only since the early 1990s that the world really began to understand what Colossus was and the way that it helped the British crack the Enigma codes. I got a chance to visit as part of Road Trip 2011, and being able to see the re-creations of the machines that cracked the Enigma codes was one of the highlights of the project.

Polish mathematicians had figured Enigma out in 1932 and had in fact fashioned a reconstruction of it. The problem was that in the early days, Enigma's cypher was changed infrequently. But with the outbreak of war, the Germans changed the cypher at least daily. Though the Poles were unable to solve the rapidly changing Enigma code, they transferred their knowledge to the French and British, who promptly put their best code breakers on the job. Those people, whose jobs were so top secret they were not allowed to talk about their work for years after the war, were able to advance the knowledge of the way the Enigma keys were connected to its electrical circuits--something that was not possible without the Polish Enigma machine to work on.

With this, the teams exploited an Enigma weakness, according to the Bletchley Park Web site: "A fundamental design flaw meant that no letter could ever be encrypted as itself; an A in the original message, for example, could never appear as an A in the code," the Web site reads. "This gave the code breakers a toehold. Errors in messages sent by tired, stressed or lazy German operators also gave clues. In January 1940 came the first break into Enigma.

"It was in Huts 3,6,4 and 8 [at Bletchley Park] that the highly effective Enigma decrypt teams worked. The huts operated in pairs and, for security reasons, were known only by their numbers...Their raw material came from the 'Y' Stations: a web of wireless intercept stations dotted around Britain and in a number of countries overseas. These stations listened in to the enemy army's radio messages and sent them to Bletchley Park to be decoded and analyzed.

"To speed up the code breaking process, the brilliant mathematician Alan Turing developed an idea originally proposed by Polish cryptanalysts. The result was the Bombe: an electro-mechanical machine that greatly reduced the odds, and thereby the time required, to break the daily-changing Enigma keys."

And then there was the effort to crack the high command's codes. According to Tony Sale, who was the first curator of the Bletchley Park Museum and who spearheaded the efforts to rebuild Colossus--it was destroyed, as was its design documents, after the war--the first information about the machine began to come to light in the 1970s.

"When I and some colleagues started, in 1991, the campaign to save Bletchley Park from demolition by property developers, I was working at the Science Museum in London restoring some early British computers," Sale writes on his Web site, Codes and Ciphers. "I believed it would be possible to rebuild Colossus. Nobody believed me.

"In 1993, I gathered together all the information available. This amounted to the eight 1945 wartime photographs taken of Colossus plus some fragments of circuit diagrams, which some engineers had kept quite illegally, as engineers always do."

And from there the work began--to find a way to re-create the plans for Colossus and then to build a new, fully functional version of the code-breaking machine. And if you take the train from Euston Station in London, or drive your way to Bletchley and visit the National Museum of Computing at Bletchley Park, where the rebuilt machine, and many others used in the battle against the Germans, are kept, you can get a rare view of one of the most important stories in the history of World War II and what it took to defeat the Nazis.

But while you're there, keep an eye for Sale, one of the true heroes of World War II history. Were it not for his efforts and those like him, we wouldn't know much about how the Allies cracked the Enigma code. But you're more likely to find Sale with a screwdriver in hand, tending to George, his humanoid robot. It was featured in a Wallace & Gromit movie, and it was the first-ever walking humanoid robot. It didn't win the war, but with its smile, it will certainly win your attention.

Correction (Monday, 3:34 p.m. PDT): This article has been modified to correct errors that confused work done at Bletchley Park on Colossus with that done there on the Bombe machine.