In 1943, capitalizing on human error in the use of Tunny, British cryptanalysts were able to crack the system — in theory, at least. "In practice, individual Tunny messages required too much processing time for use in military operations," the NSA said. So to cut down Tunny message decryption time from weeks to hours, British engineers and cryptanalysts built the first large-valve programmable computer, Colossus.
The programmable Colossus Mark 1 system, which used 1,500 vacuum tubes to calculate, helped crack the secret codes of the Third Reich and speed up the end of World War II. By June 1944, subsequent Colossus machines using 2,000 valves were cracking German high-command codes to pave the way for D-Day.
This is a picture of the Colossus Mark II, still residing at the Bletchley Park in England, on which a group of enthusiasts worked for nearly a decade to rebuild. The British government had dismantled it to prevent any Cold War enemy from discovering such advanced technology.
Credit: Colossus Rebuild Project
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