An Enigma Machine
A German Enigma cipher machine, on display in Warsaw, used to encrypt military communications before and during World War II.
Polish mathematicians Marian Rejewski, Jerzy Różycki, and Henryk Zygalski first broke the daily-changing settings of the German Enigma cipher in the early 1930s, reconstructing its wiring through mathematics alone before ever seeing a genuine military machine. In July 1939, with war looming, Polish intelligence handed their techniques and working Enigma replicas to British and French codebreakers — a gift that gave Alan Turing's team at Bletchley Park its crucial head start. The intelligence they extracted, code-named Ultra, is credited by many historians with shortening the Second World War by a significant margin, though its existence remained secret for decades afterward.
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