German submarine ''U-21'' was a

Type IIB In theoretical physics, type II string theory is a unified term that includes both type IIA strings and type IIB strings theories. Type II string theory accounts for two of the five consistent superstring theory, superstring theories in ten dimens ...

U-boat U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. Although at times they were efficient fleet weapons against enemy naval warships, they were most effectively used in an economic warfare role ...

Nazi Germany Nazi Germany (lit. "National Socialist State"), ' (lit. "Nazi State") for short; also ' (lit. "National Socialist Germany") (officially known as the German Reich from 1933 until 1943, and the Greater German Reich from 1943 to 1945) was ...

's ''

Kriegsmarine The (, ) was the navy of Germany from 1935 to 1945. It superseded the Imperial German Navy of the German Empire (1871–1918) and the inter-war (1919–1935) of the Weimar Republic. The was one of three official branches, along with the a ...

''. Her keel was

laid down Laying the keel or laying down is the formal recognition of the start of a ship's construction. It is often marked with a ceremony attended by dignitaries from the shipbuilding company and the ultimate owners of the ship. Keel laying is one o ...

4 March 1936, by Germaniawerft of

Kiel Kiel () is the capital and most populous city in the northern Germany, German state of Schleswig-Holstein, with a population of 246,243 (2021). Kiel lies approximately north of Hamburg. Due to its geographic location in the southeast of the J ...

as yard number 551. She was commissioned on 3 August 1936. During

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

, she conducted operations against enemy shipping. ''U-21'' went on seven war patrols, sinking five merchant ships and damaging one warship.

Design

German Type IIB submarine The Type II U-boat was designed by Nazi Germany as a coastal U-boat, modeled after the CV-707 submarine, which was designed by the Dutch dummy company NV Ingenieurskantoor voor Scheepsbouw Den Haag (I.v.S) (set up by Germany after World War I ...

s were enlarged versions of the original Type IIs. ''U-21'' 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 A submarine hull has two major components, the ''light hull'' and the ''pressure hull''. The light hull (''casing'' in British usage) of a submarine is the outer non-watertight hull which provides a hydrodynamically efficient shape. The pressure ...

length of , a

beam Beam may refer to: Streams of particles or energy *Light beam, or beam of light, a directional projection of light energy **Laser beam *Particle beam, a stream of charged or neutral particles **Charged particle beam, a spatially localized grou ...

of , a height of , and a draught of . The submarine was powered by two MWM RS 127 S four-stroke, six-cylinder

diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-call ...

s 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

propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...

s. 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-21'' was fitted with three

torpedo tube A torpedo tube is a cylindrical device for launching torpedoes. There are two main types of torpedo tube: underwater tubes fitted to submarines and some surface ships, and deck-mounted units (also referred to as torpedo launchers) installed aboa ...

s at the bow, five

torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, su ...

es 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-21''s first patrol was relatively uneventful. On her second foray, the boat was attacked by the British submarine which fired six

es at her in the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

northeast of

Berwick-Upon-Tweed Berwick-upon-Tweed (), sometimes known as Berwick-on-Tweed or simply Berwick, is a town and civil parish in Northumberland, England, south of the Anglo-Scottish border, and the northernmost town in England. The 2011 United Kingdom census recor ...

n the English/Scottish borderon 17 September 1939. These were the first submarine weapons launched by the

Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against F ...

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, . 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 southeast of

Buchan Ness Buchan is an area of north-east Scotland, historically one of the original provinces of the Kingdom of Alba. It is now one of the six committee areas and administrative areas of Aberdeenshire Council, Scotland. These areas were created by th ...

(near Peterhead). She also damaged the British cruiser with a mine. On her fifth sortie, she sank ''Mars'' on 21 December 1939 and ''Carl Henckel'' (both from Sweden).

Sixth patrol

Patrol number six saw her sink the Danish ''Vidar'' east of the

Moray Firth The Moray Firth (; Scottish Gaelic: ''An Cuan Moireach'', ''Linne Mhoireibh'' or ''Caolas Mhoireibh'') is a roughly triangular inlet (or firth) of the North Sea, north and east of Inverness, which is in the Highland council area of north of Scotl ...

on 31 January 1940.

Seventh patrol

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 Kristiansand is a seaside resort city and municipality in Agder county, Norway. The city is the fifth-largest and the municipality the sixth-largest in Norway, with a population of around 112,000 as of January 2020, following the incorporation ...

for repairs and released on 9 April after the German occupation of the Nordic country.

Fate

In July she was transferred to the

21st U-boat Flotilla ''21st U-boat Flotilla'' ("21. Unterseebootsflottille") was a unit of Nazi Germany's '' Kriegsmarine'' before and during World War II. It was formed in 1935 as a ''Schulverband'' ("School Unit") based at Kiel under the command of ''Kapitän zur See ...

in Kiel as a training boat, with whom she remained for the rest of the war. ''U-21'' was scrapped in February 1945.

Summary of raiding history

References

Notes

Citations

Bibliography

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External links

* * {{DEFAULTSORT:U0021 German Type II submarines U-boats commissioned in 1936 World War II submarines of Germany 1936 ships Ships built in Kiel Grounded U-boats Maritime incidents in March 1940