Colossus: The Secrets of Bletchley Park's Codebreaking Computers

Colossus: The Secrets of Bletchley Park's Codebreaking Computers

Colossus: The Secrets of Bletchley Park's Codebreaking Computers

Colossus: The Secrets of Bletchley Park's Codebreaking Computers


The American ENIAC is customarily regarded as having been the starting point of electronic computation. This book rewrites the history of computer science, arguing that in reality Colossus--the giant computer built by the British secret service during World War II--predates ENIAC by two years.

Colossus was built during the Second World War at the Government Code and Cypher School at Bletchley Park. Until very recently, much about the Colossus machine was shrouded in secrecy, largely because the code-breaking algorithms that were employed during World War II remained in use by the British security services until a short time ago. In addition, the United States has recently declassified a considerable volume of wartime documents relating to Colossus. Jack Copeland has brought together memoirs of veterans of Bletchley Park--the top-secret headquarters of Britain's secret service--and others who draw on the wealth of declassified information to illuminate the crucial role Colossus played during World War II. Included here are pieces by the former WRENS who actually worked the machine, the scientist who pioneered the use of vacuum tubes in data processing, and leading authorities on code-breaking and computer science.

A must read for anyone curious about code-breaking or World War II espionage,Colossusoffers a fascinating insider's account of the world first giant computer, the great great grandfather of the massive computers used today by the CIA and the National Security Agency.


The story of the Enigma cipher machine and its defeat by the Bletchley Park codebreakers astounded the world. This book describes Bletchley’s success against a later and more advanced German cipher machine that the British codenamed Tunny (see photograph 28). How Bletchley Park broke Tunny has been a closely guarded secret since the end of the war.

Unlike Enigma, which dated from 1923 and was marketed openly throughout Europe, the ultra-secret Tunny was created by scientists of Hitler’s Third Reich for use by the German Wehrmacht. Tunny was technologically more sophisticated than Enigma and—theoretically—more secure. From 1942 Hitler and the German High Command in Berlin relied increasingly on Tunny to protect their communications with Army Group commanders across Europe. The Tunny network carried the highest grade of intelligence.

Tunny messages sent by radio were first intercepted by the British in June 1941. After a year-long struggle with the new cipher, Bletchley Park had its first successes against Tunny in 1942. Broken Tunny messages contained intelligence which changed the course of the war, saving an incalculable number of lives.

Central to the Bletchley attack on Tunny was Colossus, the world’s first large-scale electronic digital computer. The first Colossus was built during 1943 by Thomas H. Flowers and his team of engineers and wiremen, a tightknit group who worked in utmost secrecy and at terrific speed. The construction of the machine took them ten months, working day and night, pushing themselves until (as Flowers said) their ‘eyes dropped out’.

The racks of complex electronic equipment were transferred from Flowers’ laboratory at Dollis Hill in London to Bletchley Park, where Colossus was reassembled. Despite the fact that no such machine had previously been . . .

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