B-Dienst

The B-Dienst (Beobachtungsdienst) (surveillance service) was a German naval codebreaking organisation. During World War II, B-Dienst solved British Naval Cypher No. 3, providing intelligence for the Battle of the Atlantic, until the British Admiralty introduced Naval Cypher No. 5 on 10 June 1943. B-Dienst also solved a number of merchant codes.