1942: Jerzy Różycki, Polish Cipher Bureau mathematician, died.
In 1929, while still a student, Różycki, proficient in German, was one of twenty-odd Poznań University mathematics students who accepted an invitation to attend a secret cryptology course organized at a nearby military installation by the Polish General Staff's Cipher Bureau, headquartered in Warsaw.
From September 1932 Różycki served as a civilian cryptologist with the Polish General Staff's Cipher Bureau, housed till 1937 in Warsaw's Saxon Palace. He worked there together with fellow Poznań University mathematics alumni and Cipher Bureau cryptology-course graduates Marian Rejewski and Henryk Zygalski.
The deciphering of the mathematical basis of the Enigma, and the construction of a copy of the coding machine were the work of Polish mathematicians from the General Staff Code Bureau 4 (BS4): Marian Rejewski, Jerzy Różycki and Henryk Zygalski, who broke the Enigma secret in 1932 and started to read the German secret dispatches. Based on their research, Warsaw based AVA company built several copies of the Enigma machine in 1933.
After Rejewski had reconstructed the German military Enigma machine in December 1932, Różycki and Zygalski likewise worked at ongoing development of methods and equipment to exploit Enigma decryption as a source of intelligence. Różycki invented the "clock" method, which sometimes made it possible to determine which of the machine's rotors was at the far right, that is, in the position where the rotor always revolved at every depression of a key.