Officers of  the <a href="https://en.wikipedia.org/wiki/Biuro_Szyfr%C3%B3w" class="extiw" title="en:Biuro Szyfrów">Biuro Szyfrów</a> (Cipher Bureau) - Polish General Staff's Second Department's organizational unit charged with SIGINT and both cryptography (the use of ciphers and codes) and cryptanalysis (the study of ciphers and codes, particularly for the purpose of "breaking" them). From the left: <a href="https://pl.wikipedia.org/wiki/Jakub_Plezia" class="extiw" title="pl:Jakub Plezia">Jakub Plezia</a>, Jerzy Suryn, Yamawaki Masataka, Paweł Misiurewicz, <a href="https://pl.wikipedia.org/wiki/Franciszek_Pokorny" class="extiw" title="pl:Franciszek Pokorny">Franciszek Pokorny</a>, <a href="https://pl.wikipedia.org/wiki/Maksymilian_Ci%C4%99%C5%BCki" class="extiw" title="pl:Maksymilian Ciężki">Maksymilian Ciężki</a>
unknown-anonymous
<a href="https://pl.wikipedia.org/wiki/Centralne_Archiwum_Wojskowe" class="extiw" title="pl:Centralne Archiwum Wojskowe">Centralne Archiwum Wojskowe</a>