Colossus

Colossus computer

Colossus, the first large-scale electronic computer, which went into operation in 1944 at Britain’s wartime code-breaking headquarters at Bletchley Park.

During World War II the British intercepted two very different types of encrypted German military transmissions: Enigma, broadcast in Morse code, and then from 1941 the less-well-known “Fish” transmissions, based on electric teleprinter technology. The most important source of Fish messages was a German cipher machine that the British code-named “Tunny.” Tunny was the Schlüsselzusatz (SZ) cipher attachment, manufactured by Berlin engineering company C. Lorenz AG. Tunny sent its messages in binary code—packets of zeroes and ones resembling the binary code used inside present-day computers.

Tunny encrypted top-level messages from Hitler and his army high command in Berlin. The messages went by radio to the field marshals and generals fighting at the battlefronts in Europe and North Africa. After a lengthy struggle, British code breakers broke the new cipher in 1942, and it was soon realized that Tunny rivaled, or even exceeded, Enigma in importance. Colossus was built to carry out a fundamental stage of the Tunny code-breaking process—at electronic speed.