B-Dienst: the German Navy Signals Intelligence Service. One of their great triumphs was breaking the code the Allies used to give instructions to merchant convoys. This was finally discovered by the US Navy in mid 1943 and the code was replaced.
Charles McCain is a Washington DC based freelance journalist and novelist. He is the author of "An Honorable German," a World War Two naval epic. You can read more of his work on his website: http://charlesmccain.com/ View all posts by Charles McCain