Enigma

Polish codebreakers crack the Enigma secret

In 1932, three Polish mathematicians — Marian Rejewski, Jerzy Różycki, and Henryk Zygalski — were the first in the world to break the German Enigma cipher, giving the Allies invaluable intelligence advantage. Their achievements, passed to France and Britain in 1939, became the foundation of Project Ultra and contributed to shortening World War II by several years. The Polish breakthrough remained classified for decades, only recognized after archives were declassified.