German submarine U-21 (1936)

U-9, a typical Type IIB boat
History
Nazi Germany
Name:	U-21
Fate:	Stranded, March 1940 after running aground in southern Norway
General characteristics
Class and type:	IIB coastal submarine
Displacement:	279 t (275 long tons) surfaced 328 t (323 long tons) submerged
Length:	42.70 m (140 ft 1 in) o/a 27.80 m (91 ft 2 in) pressure hull
Beam:	4.08 m (13 ft 5 in) (o/a) 4.00 m (13 ft 1 in) (pressure hull)
Height:	8.60 m (28 ft 3 in)
Draught:	3.90 m (12 ft 10 in)
Installed power:	700 PS (510 kW; 690 bhp) (diesels) 410 PS (300 kW; 400 shp) (electric)
Propulsion:	2 shafts 2 × diesel engines 2 × electric motors
Range:	1,800 nmi (3,300 km; 2,100 mi) at 12 knots (22 km/h; 14 mph) surfaced 35–43 nmi (65–80 km; 40–49 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged
Test depth:	80 m (260 ft)
Complement:	3 officers, 22 men
Armament:	3 × 53.3 cm (21 in) torpedo tubes 5 × torpedoes or up to 12 TMA or 18 TMB 1 × 2 cm (0.79 in) anti-aircraft gun
Service record
Part of:	Kriegsmarine 1st U-boat Flotilla 3rd U-boat Flotilla 21st U-boat Flotilla 30th U-boat Flotilla
Commanders:	Kptlt. Kurt Freiwald 18 July 1935 – 3 October 1937 Kptlt. Werner Lott September 1936 – 31 March 1937 Kptlt. Wilhelm Ambrosius 1937 Kpt. Erwin Sachs 1937 Kptlt. Fritz Frauenheim 1 October 1937 – 6 January 1940 Wolf-Harro Stiebler 6 January – 28 July 1940 Oblt.z.S. Hans Heidtmann 1 August – 20 December 1940 Kptlt. Ernst-Bernard Lohse 21 December 1940 – 18 May 1941 Oblt.z.S. Karl-Heinz Herbsleb 19 May 1941 – 3 January 1942 Oblt.z.S. Hans-Heinrich Döhler 4 January – 24 September 1942 Lt.z.S. Hans-Ferdinand Geisler 25 September 1942 – 28 January 1943 Oblt.z.S. Rudolf Kugelberg 29 January 1943 – 11 May 1944 Oblt.z.S. Wolfgang Schwazkopf 12 May – 5 August 1944
Operations:	16; 1st patrol: 25 August – 5 September 1939 2nd patrol: 9 September – 1 October 1939 3rd patrol: 22 October – 8 November 1939 4th patrol: 27 November – 5 December 1939 5th patrol: 17–24 December 1939 6th patrol: 27 January – 9 February 1940 7th patrol: 21–27 March 1940
Victories:	Five ships sunk for a total of 10,706 GRT one auxiliary warship sunk, of 605 GRT; one warship damaged of 11,500 tons

German submarine U-21 was a Type IIB U-boat of Nazi Germany's Kriegsmarine. Her keel was laid down 4 March 1936, by Germaniawerft of Kiel as yard number 551. She was commissioned on 3 August 1936. During World War II, she conducted operations against enemy shipping.

U-21 went on seven war patrols, sinking five ships, one auxiliary warship and damaging one warship.

German Type IIB submarines were enlarged versions of the original Type IIs. U-21 had a displacement of 279 tonnes (275 long tons) when at the surface and 328 tonnes (323 long tons) while submerged. Officially, the standard tonnage was 250 long tons (250 t), however. The U-boat had a total length of 42.70 m (140 ft 1 in), a pressure hull length of 28.20 m (92 ft 6 in), a beam of 4.08 m (13 ft 5 in), a height of 8.60 m (28 ft 3 in), and a draught of 3.90 m (12 ft 10 in). The submarine was powered by two MWM RS 127 S four-stroke, six-cylinder diesel engines of 700 metric horsepower (510 kW; 690 shp) for cruising, two Siemens-Schuckert PG VV 322/36 double-acting electric motors producing a total of 460 metric horsepower (340 kW; 450 shp) for use while submerged. She had two shafts and two 0.85 m (3 ft) propellers. The boat was capable of operating at depths of up to 80–150 metres (260–490 ft).

The submarine had a maximum surface speed of 12 knots (22 km/h; 14 mph) and a maximum submerged speed of 7 knots (13 km/h; 8.1 mph). When submerged, the boat could operate for 35–42 nautical miles (65–78 km; 40–48 mi) at 4 knots (7.4 km/h; 4.6 mph); when surfaced, she could travel 3,800 nautical miles (7,000 km; 4,400 mi) at 8 knots (15 km/h; 9.2 mph). U-21 was fitted with three 53.3 cm (21 in) torpedo tubes at the bow, five torpedoes or up to twelve Type A torpedo mines, and a 2 cm (0.79 in) anti-aircraft gun. The boat had a complement of twentyfive.