U-9, a typical Type IIB boat
|Ordered||2 February 1935|
|Laid down||4 March 1936|
|Launched||31 July 1936|
|Commissioned||3 August 1936|
|Fate||Decommissioned on 5 August 1944 at Pillau and cannibalized for spare parts|
|Class and type||Type IIB coastal submarine|
|Height||8.60 m (28 ft 3 in)|
|Draught||3.90 m (12 ft 10 in)|
|Test depth||80 m (260 ft)|
|Complement||3 officers, 22 men|
|Identification codes:||M 08 360|
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 merchant ships 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.
First, second and third patrols
U-21's first patrol was relatively uneventful.
On her second foray, the boat was attacked by the British submarine HMS Ursula which fired six torpedoes at her in the North Sea northeast of Berwick-Upon-Tweed [On the English/Scottish border] on 17 September 1939. These were the first submarine weapons launched by the Royal Navy in the Second World War. They all missed.
On her third patrol, the U-boat also had torpedoes fired at her in the central North Sea by another British submarine, HMS Sealion. The result was inconclusive as well.
Fourth and fifth patrols
The boat's first success with a torpedo came on 1 December 1939 when she sank the Finnish-registered Mercator about 12 nmi (22 km; 14 mi) southeast of Buchan Ness (near Peterhead). She also damaged the British cruiser HMS Belfast with a mine.
On her fifth sortie, she sank Mars on 21 December 1939 and Carl Henckel (both from Sweden).
She sank the British Royal Archer with a mine on 26 February 1940, but then it all went horribly wrong on 27 March when she ran aground off Oldknuppen Island after a navigational error. The boat was towed to Mandal in Norway where she was interned. She was then towed to Kristiansand for repairs and released on 9 April after the German occupation of the Nordic country.
Summary of raiding history
|21 November 1939||HMS Belfast||Royal Navy||11,500||Damaged (mine)|
|1 December 1939||Mercator||Finland||4,260||Sunk|
|21 December 1939||Carl Henckel||Sweden||1,352||Sunk|
|21 December 1939||Mars||Sweden||1,475||Sunk|
|31 January 1940||Vidar||Denmark||1,353||Sunk|
|24 February 1940||Royal Archer||United Kingdom||2,266||Sunk (mine)|
- Busch, Rainer; Röll, Hans-Joachim (1999). German U-boat commanders of World War II : a biographical dictionary. Translated by Brooks, Geoffrey. London, Annapolis, Md: Greenhill Books, Naval Institute Press. ISBN 1-55750-186-6.
- Busch, Rainer; Röll, Hans-Joachim (1999). Deutsche U-Boot-Verluste von September 1939 bis Mai 1945 [German U-boat losses from September 1939 to May 1945]. Der U-Boot-Krieg (in German). Vol. IV. Hamburg, Berlin, Bonn: Mittler. ISBN 3-8132-0514-2.
- Gröner, Erich; Jung, Dieter; Maass, Martin (1991). U-boats and Mine Warfare Vessels. German Warships 1815–1945. Vol. 2. Translated by Thomas, Keith; Magowan, Rachel. London: Conway Maritime Press. ISBN 0-85177-593-4.
- Helgason, Guðmundur. "The Type II boat U-21". German U-boats of WWII – uboat.net. Retrieved 6 December 2014.
- Hofmann, Markus. "U 21". Deutsche U-Boote 1935–1945 – u-boot-archiv.de (in German). Retrieved 6 December 2014.