Ignacy Witczak was a GRU Illegal officer in the United States during World War II.
Witczak's code name with the GRU and as deciphered by the Venona project and other counterintelligence investigations was "R".
Evidence of espionage
Ignacy Witczak is referenced in the following Venona decryptions and FBI reports:
References
Ignacy Witczak Wikipedia(Text) CC BY-SA