The senior Petty Officer aboard a German submarine was the Oberbootsmann. This position was normally filled by a long service regular German Navy man. He was responsible for the crew and overall discipline in the boat. The equivalent rank in the U.S Navy is Chief Bosun’s Mate, or, more formally, the Chief Boatswain’s Mate.
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