She was laid down as the merchant ship Ems at the yard of Bremen Vulkan, DeSchiMAG 16 January 1937 building no.7 for account of the Norrdeutscher Lloyd and bought by the German Kriegsmarine in 1939. After being fitted out as an auxiliary cruiser was she commissioned 2 June 1940. According to the German administration she was known as Schiff 45 [Ship No. 45) while the British Royal Navy knew her as the Raider B. She was also known as the HSK-7. She sunk due to a torpedo fired by a British MTB off Cape de la Hague on 14 October 1942 with loss of all men.
With a displacement of 7,500 tons or 3,287 tons GRT were her dimensions 115,5 x 15,3 x 6,5 metres. Her two diesel engines allowed a speed of 16 knots while she had a range of 35,100 nautical miles. Her crew numbered 274 men. When fitted out she was armed with 6-15cm guns, 1-7,5cm gun, 1-3,7cm gun, 4-2cm anti aircraft guns, 6-53,3cm torpedo tubes, 30 EMC mines (for laying this she had a small fast LS2-class boat called Meteorit on board) and she carried with her one or two Arado Ar 196 A-1 sea planes.