Some of the earliest supercomputers that could be considered as such were developed during the late 1930s and early 1940s. Though mechanical calculating devices had existed earlier, these were the first devices that were electrically operated and carried out calculations in a series of steps.
In 1936 the British mathematician Alan Turing wrote a paper describing a machine that could be used to perform any calculation that could be calculated, laying some important groundwork for the idea of the computer. As one of the leading lights of the British effort to crack the German Enigma code, he also introduced Royal Mail telephone engineer Tommy Flowers to Max Newman, under whose supervision Flowers built Colossus, an early British computer.
The first electrically-driven computer that counted in binary was made by Konrad Zuse, a German civil engineer, in the late 1930s. By 1941 his Z3 was fully functioning and what would later be called Turing-complete i.e. theoretically able to carry out any computation, given enough time. Unfortunately, being from Germany meant that Zuse did not receive worldwide recognition for his achievements until long after the Second World War, despite none of his work ever having being used by the Nazi government.