British intelligence has released new photos showing the World War II era "Colossus" computer.
It marked the 80th anniversary of the code-breaking computer's invention.
The device's existence was largely kept secret until the early 2000s.
British intelligence has released "rare and never-before-seen images" of the World War II era "Colossus" code-breaking computer.
GCHQ, the UK's intelligence, security and cyber agency, said in a press release that the new photos were released to celebrate the 80th anniversary of the computer's invention.
Colossus, which was shrouded in secrecy until the early 2000s, was designed by engineer Tommy Flowers to decipher coded messages between some of Nazi Germany's most senior officers.
It played a key role in helping the Allies win World War II. It provided critical intelligence that German leader Adolf Hitler had been duped into believing the Allies would invade occupied France via Pas-de-Calais rather than Normandy, where they would carry out the famous and pivotal D-Day landings on June 6, 1944 — codenamed Operation Overlord.
The huge machine was at the cutting edge of technology for its time, contained 2,500 valves, and was a precursor to the computer age.
GCHQ said the images shed "new light on the genesis and workings of Colossus, which was over two meters tall and considered by many to be the first-ever digital computer."
Soldiers from the Women's Royal Naval Service (Wrens) were recruited to the large teams of operators and technicians needed to run and maintain Colossus' spy operation against Nazi Germany.
Bill Marshall, a former GCHQ engineer who worked on the computer during the 1960s, said he had to sign the "Official Secrets Act" and "was told very little" about the machine he was working on, per GCHQ.
"What the machine was actually doing was not for me to know," he added. "It wasn't until much later that I found out that the several of the systems and detailed design information were supposedly destroyed at the end of WWII."
Andrew Herbert, a computer scientist who has served as the chairman of Microsoft Research and is the chairman of trustees at The National Museum of Computing, said: "Colossus was perhaps the most important of the wartime code breaking machines because it enabled the Allies to read strategic messages passing between the main German headquarters across Europe."
Housed at the UK's code-breaking center, Bletchley Park, 10 Colossus computers helped 550 people decrypt "63 million characters of high-grade German communications" by the end of World War II, according to The National Museum of Computing.
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