German submarine U-121 (1940)

German submarine U-121 was a long-lived Type IIB U-boat built during World War II for service in Nazi Germany's Kriegsmarine. U-121 spent the entire war as a training vessel and was scuttled at the end of the conflict.

U-121 was one of two Type II U-boats built at Flender Werke in Lübeck. Like her sister boat GS U-120 (1940) (also built in Lübeck), she was originally constructed for export to China. The advent of World War II and the increased training needs of the U-Boot-Waffe led the German high command to assign U-120 and U-121 to the training command instead.

Built for China
The Chinese Nationalist Government used 10,000,000 Marks to order two Type IIB U-boats in 1937. They also dispatched 80 men to Germany for training in submarine operations. The Japanese Government complained over this transaction, so the Chinese took their money back and the pair of Type IIB submarines joined the Kriegsmarine after the outbreak of the Second World War in Europe. They were U-120 and U-121.

Design
German Type IIB submarines were enlarged versions of the original Type IIs. U-121 had a displacement of 279 t when at the surface and 328 t while submerged. Officially, the standard tonnage was 250 LT, however. The U-boat had a total length of 42.70 m, a pressure hull length of 28.20 m, a beam of 4.08 m, a height of 8.60 m, and a draught of 3.90 m. The submarine was powered by two MWM RS 127 S four-stroke, six-cylinder diesel engines of 700 PS for cruising, two Siemens-Schuckert PG VV 322/36 double-acting electric motors producing a total of 460 PS for use while submerged. She had two shafts and two 0.85 m propellers. The boat was capable of operating at depths of up to 80 - 150 m.

The submarine had a maximum surface speed of 12 kn and a maximum submerged speed of 7 kn. When submerged, the boat could operate for 35 - 42 nmi at 4 kn; when surfaced, she could travel 3800 nmi at 8 kn. U-121 was fitted with three 53.3 cm torpedo tubes at the bow, five torpedoes or up to twelve Type A torpedo mines, and a 2 cm anti-aircraft gun. The boat had a complement of twentyfive.