[Alan Turing] is credited with breaking the Enigma code in 1941. [...] After the war, Turing built on these ideas to develop something closer to the computer we recognize today. Turing’s life and tragic end by suicide following years of persecution and “treatment” for his homosexuality were immortalized in the 2014 film The Imitation Game. [...]

Shortly after the invasion of Poland by Germany in 1939, a group of cryptanalysts were evacuated to France. The group consisted of employees from the Polish Cipher Bureau who had been working on the German Enigma code. [...] Rejewski’s work on the Enigma code was very significant. As early as 1932, while still in Poland, he developed an in-depth understanding of how the machine worked. He even managed to reconstruct its internal wiring without ever having seen the machine.

Rejewski is credited with doing groundbreaking work that allowed the code finally to be broken by Turing in 1941.

Rejewski returned to Poland after the war. For a long time, he kept quiet about his remarkable code breaking skills to avoid the government becoming interested in him. [...]

Due to the secretive nature of their work, many cryptanalysts never received recognition for their work until many years later. But their contribution to the war effort was hugely significant.