B-Dienst
The B-Dienst (German: Beobachtungsdienst, observation service), also called xB-Dienst, X-B-Dienst and χB-Dienst, was a Department of the German Naval Intelligence Service (German: Marinenachrichtendienst, MND III) of the OKM that dealt with the interception and recording, decoding and analysis of the enemy. In particular, it focused on British radio communications before and during World War II. B-Dienst worked on cryptanalysis and deciphering (decrypting) of enemy and neutral states' message traffic and security control of Kriegsmarine key processes and machinery.