German submarine U-20 was a Type IIB U-boat of Nazi Germany's Kriegsmarine. Her keel was laid down on 1 August 1935, by Germaniawerft of Kiel as yard number 550. She was commissioned on 1 February 1936. During World War II, she conducted operations against enemy shipping. U-20 went on 16 war patrols, sinking 13 ships totalling and 9 tons , damaging one more of . Design German Type IIB submarines were enlarged versions of the original Type IIs. U-20 had a displacement of when at the surface and while submerged. Officially, the standard tonnage was , however. The U-boat had a total length of , a pressure hull length of , a beam of , a height of , and a draught of . The submarine was powered by two MWM RS 127 S four-stroke, six-cylinder diesel engines of for cruising, two Siemens-Schuckert PG VV 322/36 double-acting electric motors producing a total of for use while submerged. She had two shafts and two propellers. The boat was capable of operating at depths of up to . The submarine had a maximum surface speed of and a maximum submerged speed of . When submerged, the boat could operate for at ; when surfaced, she could travel at . U-20 was fitted with three torpedo tubes at the bow, five torpedoes or up to twelve Type A torpedo mines, and a anti-aircraft gun. The boat had a complement of twentyfive. Operational history First, second and third patrols U-20s first three patrols involved observation (in August 1939) and the laying of mines in the North Sea and off the British east coast. She would start in Kiel and finish in Wilhelmshaven; then reverse the process. Fourth and fifth patrols She sank Magnus about east northeast of Peterhead in Scotland. The ship went down in 90 seconds; there was only one survivor. She also sank Ionian and Willowpool in November and December respectively, with mines laid in November. The boat sank Sylvia northeast of Aberdeen on her fifth sortie on 13 October 1940. Sixth to eighth patrols U-20 sank a steady number of ships on her sixth and seventh patrols, (her eighth foray was relatively quiet), but a series of changes were on the way. She was transferred to the U-Ausbildungsflottille as a school boat on 1 May 1940, then the Black Sea, avoiding the heavy British presence at Gibraltar and throughout the Mediterranean