View source for Type XXI submarine

{{Short description|German World War II submarine class}}
{{Infobox ship
|section1={{Infobox ship/image
 | image = 2004-Bremerhaven_U-Boot-Museum-Sicherlich_retouched.jpg
 | image_caption = {{GS|U-2540||2}} in wartime configuration and exhibited at the Maritime Museum in Bremerhaven. It is the only floating example of a Type XXI U-boat.
 }}

|section2={{Infobox ship/class overview
 | name = Type XXI
 | builders = *[[Blohm+Voss]]
              *[[AG Weser]]
              *[[Schichau-Werke]]
 | operators = *{{navy|Nazi Germany|name=''Kriegsmarine''}}
               *''Postwar:''
               *{{navy|France}}
               *{{navy|West Germany}}
               *{{navy|United Kingdom}}
               *{{navy|Soviet Union}}
               *{{navy|United States|1912}}
 | class_before = *[[Type VII Submarine|Type VII]] (patrol submarine)
                  *[[Type IX submarine|Type IX]] (oceanic submarine)
                  *[[Type XVIII submarine|Type XVIII]] (cancelled oceanic AIP project)
 | class_after = [[Type XXVI submarine|Type XXVI]] (none completed)
 | cost = {{Reichsmark|5,750,000|link=yes}} per boat{{sfn|Gröner|Jung|Maass|1991|p=84–85}}
 | built_range = 1943–1945{{sfn|Gröner|Jung|Maass|1991|p=84–85}}
 | in_service_range = 
 | in_commission_range = 1944–1982
 | total_ships_building = 267{{sfn|Gröner|Jung|Maass|1991|pp=84–89}}
 | total_ships_planned = 1,170{{sfn|Gröner|Jung|Maass|1991|pp=84–89}}
 | total_ships_completed = 118
 | total_ships_canceled = 785{{sfn|Gröner|Jung|Maass|1991|pp=84–89}}
 | total_ships_active = 
 | total_ships_laid_up = 
 | total_ships_lost = 
 | total_ships_retired = 
 | total_ships_preserved = 1
 }}

|section3={{Infobox ship/characteristics
 | hide_header = 
 | header_caption = 
 | class = 
 | displacement = *{{convert|1,621|t|LT|lk=on|abbr=on}} surfaced
                  *{{convert|1,819|t|LT|abbr=on}} submerged{{sfn|Gröner|Jung|Maass|1991|p=84–85}}
 | length = *{{convert|76.70|m|ftin|abbr=on}}{{sfn|Gröner|Jung|Maass|1991|p=84–85}}
 | beam = *{{convert|8|m|ftin|abbr=on}}{{sfn|Gröner|Jung|Maass|1991|p=84–85}}
 | draught = {{convert|6.32|m|ftin|abbr=on}}{{sfn|Gröner|Jung|Maass|1991|p=84–85}}
 | propulsion = *Geared Diesel/Geared battery-electric/CODABEL/Diesel-electric beltdrive/Low-noise electric beltdrive.
                *2× [[MAN SE|MAN]] M6V40/46KBB geared supercharged 6-cylinder [[diesel engine]]s, {{convert|4000|PS|shp kW|lk=on|abbr=on}}, driving:
                *2× [[Siemens-Schuckert|SSW]] geared GU365/30 [[Motor–generator|double-acting electric motors]], {{convert|5000|PS|shp kW|abbr=on}}{{sfn|Gröner|Jung|Maass|1991|p=84–85}}
                *2 × SSW GV232/28 "creep motors", {{convert|226|PS|shp kW|abbr=on}} for [[Silent running (submarine)|silent running]], and to keep the boat moving while the batteries are being recharged.
                *2 shafts
 | speed = *{{convert|15.6|kn}} surfaced
           *{{convert|17.2|kn}} submerged{{sfn|Gröner|Jung|Maass|1991|p=84–85}}<ref>{{Cite web|url=http://www.uboatarchive.net/Design/DesignStudiesTypeXXI.htm|title = U-boat Archive - Design Studies - Type XXI}}</ref>
           *{{Convert|6.1|kn}} (silent running motors)
 | range = *{{convert|15,500|nmi|lk=on|abbr=on}} at {{convert|10|kn}} surfaced
           *{{convert|340|nmi|abbr=on}} at {{convert|5|kn}} submerged{{sfn|Gröner|Jung|Maass|1991|p=84–85}}
 | test_depth = *{{convert|240|m|ft|0|abbr=on}}{{sfn|Gröner|Jung|Maass|1991|p=84–85}}
 | complement = 5 officers, 52 enlisted men{{sfn|Gröner|Jung|Maass|1991|p=85}}
 | armament = *6 × {{convert|53.3|cm|in|0|abbr=on}} [[torpedo tube]]s (bow)
              *23 [[G7e torpedo|G7 torpedoes]] (or 17 torpedoes and 12 [[Naval mine|mine]]s)
              * 2 x twin [[2 cm FlaK 30|{{convert|2|cm|in|sp=us|abbr=on}} C/30]] anti-aircraft guns{{sfn|Gröner|Jung|Maass|1991|p=85}}
 | type = Oceanic conventional [[Submarine]]
 | armour = *Bridge: 17mm
 }}
}}

'''Type XXI submarines''' were a class of German [[diesel–electric]] ''[[Elektroboot]]'' (German: "electric boat") [[submarine]]s designed during the [[Second World War]]. One hundred eighteen were completed, with four being combat-ready. During the war only two were put into active service and went on patrols, but these were not used in combat.

They were the first submarines designed to operate primarily submerged, rather than spending most of their time as [[surface ship]]s that could submerge for brief periods as a means of escaping detection. They incorporated many batteries to increase the time they could spend submerged, to as much as several days, and they only needed to surface to periscope depth for recharging via a [[Submarine snorkel|snorkel]]. The design included many general improvements as well: much greater underwater speed by an improved hull design, greatly improved diving times, power-assisted torpedo reloading and greatly improved crew accommodations. However, the design was also flawed in many ways, with the submarines being mechanically [[unreliable]]<ref>Jones, Marcus O. (2014) "Innovation for Its Own Sake: The Type XXI U-boat", ''Naval War College Review'', Vol. 67, No. 2, Article 9  https://digital-commons.usnwc.edu/nwc-review/vol67/iss2/9|{{Dead link|date=October 2022 |bot=InternetArchiveBot |fix-attempted=yes }} p10 "Early Type XXI hulls suffered from defective diesel-engine superchargers, faulty hydraulic torpedo-loading systems, trouble-prone steering systems..."</ref> and, according to post-war analysis, vulnerable to combat damage. The Type XXI submarines were also rushed into production before design work was complete, and the inexperienced facilities which constructed the boats were unable to meet necessary quality standards.

After the war, several navies obtained Type XXIs and operated them for decades in various roles, while large navies introduced new submarine designs based on them. These include the Soviet {{sclass|Whiskey|submarine|5}}, American {{sclass|Tang|submarine|5}}, British [[British Porpoise-class submarine|''Porpoise'']], and Swedish {{sclass|Hajen III|submarine|5}} classes, all based on the Type XXI design to some extent.<ref>{{cite web |url=http://www.hisutton.com/World-Submarine-Family-Tree.html |title= World-Submarine-Family-Tree |author= H I Sutton |date=7 March 2021|website= Covert Shores}}</ref>

==Description==
The main features of the Type XXI were the hydrodynamically streamlined hull and [[conning tower]] and the large number of [[Battery cell|battery cells]], roughly triple that of the [[Type VII submarine]]. This gave these boats great underwater range and dramatically reduced the time spent on or near the surface. They could travel submerged at about {{convert|5|kn|lk=in}} for about 75 hours<ref>{{cite book|url=https://books.google.com/books?id=azQVDAAAQBAJ&q=Type+XXI+u+boat+capacity+57&pg=PA57|title=Wolf Pack: The Story of the U-Boat in World War II|author=Gordon Williamson |page=59|date=February 5, 2005|publisher=Osprey|isbn=978-1841768724 |access-date=October 12, 2018}}</ref> before recharging batteries, which took less than five hours using the [[Submarine snorkel|snorkel]] due to the new super-charged diesel engines. Being designed primarily for submerged use, the Type XXI's maximum surface speed {{nowrap|(15.6 knots)}} was lower than that of the [[Type IX submarine|Type IX]] (18.2 knots) but its submerged speed was more than twice that of the Type IX (17.2 knots versus 7.7 knots) because they were equipped with much more powerful electric drive motors and had less drag.<ref>{{Cite web|url=http://www.uboataces.com/uboat-type-ix.shtml|title = German Type IX U-Boat - history, specification and photos}}</ref><ref>{{cite book|url=https://books.google.com/books?id=azQVDAAAQBAJ&q=Type+XXI+u+boat+capacity+57&pg=PA57|title=Wolf Pack: The Story of the U-Boat in World War II|author=Gordon Williamson |page=58|date=February 5, 2005|publisher=Osprey|isbn=978-1841768724 |access-date=October 12, 2018}}</ref>

The Type XXI was also much quieter than the VIIC, making it more difficult to detect when submerged, and the design eliminated protruding components that had created drag in earlier models. The new, streamlined hull design allowed submerged speed of {{convert|17.2|kn|mph km/h|abbr=on|lk=on}}, versus   {{convert|7.6|kn|mph km/h|abbr=on|lk=on}} for the Type VIIC.<ref>{{cite web|url=https://u-boot-wilhelm-bauer.de/en/history.html|title=History, U-Boot Wilhelm-Bauer|date=October 2, 2015|website=Museum Harbour of Bremerhaven|access-date=October 11, 2018|archive-date=October 12, 2018|archive-url=https://web.archive.org/web/20181012054022/https://u-boot-wilhelm-bauer.de/en/history.html|url-status=dead}}</ref> The ability to outrun many surface ships while submerged, combined with improved dive times (also a product of the new hull form), made the Type XXI much more difficult to pursue and destroy.<ref name="Wolf Pack: The Story of the U-Boat in World War II">{{cite book|url=https://books.google.com/books?id=azQVDAAAQBAJ&q=Type+XXI+u+boat+capacity+57&pg=PA57|title=Wolf Pack: The Story of the U-Boat in World War II|author=Gordon Williamson |date=February 5, 2005|publisher=Osprey|isbn=978-1841768724 |access-date=October 12, 2018}}</ref> It also provided a sprint ability when positioning itself for an attack. Older boats had to surface to sprint into position. This often revealed a boat's location, especially after aircraft became available for convoy escort. The Type XXI was also equipped with a pair of electric "creep motors" for silent running.<ref name="Wolf Pack: The Story of the U-Boat in World War II" />

The Type XXI was equipped with six bow torpedo tubes (instead of the more common four in German submarines) and carried 23 torpedoes.<ref>{{cite book|url=https://books.google.com/books?id=azQVDAAAQBAJ&q=Type+XXI+u+boat+capacity+57&pg=PA57|title=Wolf Pack: The Story of the U-Boat in World War II|author=Gordon Williamson |date=February 5, 2005|page=59|publisher=Osprey|isbn=978-1841768724 |access-date=October 12, 2018}}</ref> 
It featured an electric [[torpedo]]-reloading system that allowed all six bow torpedo tubes to be reloaded faster than a Type VIIC could reload one tube.{{sfn|Breyer|1999|pp=18–19}} The Type XXI could fire 18 torpedoes in less than 20 minutes. The class also featured a very sensitive passive [[sonar]] for the time, housed in the "chin" of the hull.

The Type XXIs also had better facilities than previous U-boat classes, with much roomier crew berths, and a [[freezer]] to prevent food spoilage.<ref>{{cite book|last1=Gerken|first1=Louis|title=Torpedo Technology|date=1989|publisher=Pennsylvania State University|location=United States|isbn=978-0961716325|page=57|edition=Illustrated|url=https://books.google.com/books?id=6NTiAAAAMAAJ|access-date=30 June 2017}}</ref> The increased capacity allowed for a crew of 57.<ref>{{cite book|last1=Gardiner|first1=Robert|title=Warships - 1990|date=1990|publisher=Conway Maritime Press|location=London, UK|isbn=978-0851775470|page=183}}</ref><ref>{{cite book|url=https://books.google.com/books?id=azQVDAAAQBAJ&q=Type+XXI+u+boat+capacity+57&pg=PA57|title=Wolf Pack: The Story of the U-Boat in World War II|author=Gordon Williamson |date=February 5, 2005|page=60|publisher=Osprey|isbn=978-1841768724 |access-date=October 12, 2018}}</ref>

A post-war assessment of the Type XXI by the [[United States Navy]] concluded that while the design had some admirable features, it was seriously flawed.{{sfn|Blair|2000|p=x}} The submarines' engines were underpowered, which limited the surface speed and increased the time required to charge the batteries. The hydraulic system was unduly complex, and its main elements were located outside the pressure hull. This made the system highly vulnerable to corrosion and damage. The [[submarine snorkel|snorkel]] was also badly designed, and difficult to use in practice.{{sfn|Blair|2000|p=xi}}

==Construction==
[[File:Type XXI section.jpg|thumb|left|Construction consisted of nine prefabricated sections]]
This was the first U-boat to be constructed of modular components to allow for the manufacture of the various components in different factories and subsequent assembly at the shipyard.<ref name="Wolf Pack: The Story of the U-Boat in World War II" />

Between 1943 and 1945, 118 boats were assembled by [[Blohm & Voss]] of [[Hamburg]], [[AG Weser]] of [[Bremen (city)|Bremen]] and [[Schichau-Werke]] of [[Danzig]]. Each hull was constructed from nine prefabricated sections with final assembly at the shipyards. This new method allowed for a hypothetical construction time of less than six months per vessel, but in practice all the assembled U-boats were plagued with severe quality problems that required extensive post-production work and time to rectify.<ref name="Wolf Pack: The Story of the U-Boat in World War II" /> One of the reasons for these shortcomings was that sections were made by companies having little experience with shipbuilding, after a decision by [[Albert Speer]]. As a result, of 118 Type XXIs constructed, only four were fit for combat before the Second World War ended in Europe. Of these, only two conducted combat patrols and neither sank any Allied ships.<ref>{{cite book | last=Tooze | first=Adam |author-link=Adam Tooze| title=The Wages of Destruction | publisher= [[Penguin Books]]| location=London| year = 2006|isbn=978-0-14-100348-1 | pages=616–618| title-link=The Wages of Destruction }}</ref> Post-war assessments by the US Navy and British [[Royal Navy]] also found that the completed submarines had poor structural integrity due to the manufacturing problems. This rendered the submarines highly vulnerable to [[depth charge]]s, and gave them a lesser maximum diving depth than earlier U-boat designs.{{sfn|Blair|2000|p=x}}

It was planned that final assembly of Type XXI boats would eventually be carried out in the [[Valentin submarine pens]], a massive, bomb–hardened concrete bunker built at the small port of [[Farge]], near Bremen.<ref name="flower350">{{cite book |last= Flower |first= Stephen |title= Barnes Wallis' Bombs |publisher= Tempus |year= 2004 |isbn= 978-0-7524-2987-8|page=350}}</ref> The pens were constructed between 1943 and 1945, using about 10,000 concentration camp prisoners and prisoners of war as forced labour.<ref>{{cite encyclopedia | url =http://www.ushmm.org/wlc/en/article.php?ModuleId=10007390 | title =Neuengamme / Bremen-Farge | author =Marc Buggeln | encyclopedia = Holocaust Encyclopedia| publisher =United States Holocaust Memorial Museum | access-date = 29 January 2011}}</ref> The facility was 90% completed when, during March 1945, it was heavily damaged by Allied bombing with [[Grand Slam bomb|Grand Slam]] "earthquake" bombs and abandoned. A few weeks later the area was captured by the British Army.<ref name="flower351">{{cite book |last= Flower |first= Stephen |title= Barnes Wallis' Bombs |publisher= Tempus |year= 2004 |isbn= 978-0-7524-2987-8|page=351}}</ref>

Due to the combination of design and construction problems, historian [[Clay Blair]] judged that "the XXI could not have made a big difference in the [[Battle of the Atlantic]].{{sfn|Blair|2000|p=x}}

[[File:SRH025-p40.jpg|thumb|right|U.S. Navy diagram of a Type XXI U-boat. Note the teardrop-shaped fairing for the large hydrophone array beneath the bow and the wasp-waist pressure hull. The large sonar array and its housing did slow the boat down, but its placement and size allowed for a very sensitive system to be installed, and gave it near-360 degree coverage around the submarine.]]

==Sensors==

===Radar detector===
The FuMB Ant 3 ''Bali'' radar detector and antenna was located on top of the snorkel head.

===Radar transmitter===
The Type XXI boats were fitted with the [[Hohentwiel (Radar)|FuMO 65 ''Hohentwiel'' U1]] with the Type F432 D2 radar transmitter.
<gallery>
File:FuMO-61 Hohentwiel U Radar Transmitter Type F 432 D2.jpg|Radar Transmitter Type F432 D2
</gallery>

==Wartime and post-war service==

===Germany===
[[File:U2511 Bergen.jpg|thumb|Three Type XXI U-boats and one [[Type VII U-boat]] moored at [[Bergen, Norway]] (May 1945). The Type XXI in the middle is ''U-2511'']]

{{GS|U-2511||2}} and {{GS|U-3008||2}} were the only Type XXIs used for war patrols, and neither sank any ships. The commander of ''U-2511'' claimed the U-boat had a British cruiser in his sights on 4 May when news of the German cease-fire was received. He further claimed he made a practice attack before leaving the scene undetected.<ref>{{cite book | last=Van der Vat| first=Dan|author-link=Dan van der Vat| title=Stealth at Sea| publisher= Orion| location=London| year = 1994|isbn=978-1-85797-864-3 | page=353}}</ref>

During 1957, {{GS|U-2540||2}}, which had been [[Scuttling|scuttled]] at the end of the war, was raised and refitted as [[research vessel]] ''Wilhelm Bauer'' of the ''[[Bundesmarine]]''. It was operated by both military and civilian crews for research purposes until 1982. During 1984, it was made available for display to the public by the ''[[Deutsches Schiffahrtsmuseum]]'' (German Maritime Museum) in [[Bremerhaven]], Germany.

===France===
{{GS|U-2518||2}} became {{ship|French submarine|Roland Morillot|S613|6}}. It was used for active service during the [[Suez Crisis]] in 1956, and remained in commission until 1967. It was scrapped in 1969.

===Soviet Union===
Four Type XXI boats were assigned to the USSR by the [[Potsdam Agreement]]; these were  {{GS|U-2529||2}}, {{GS|U-3035||2}}, {{GS|U-3041||2}}, and {{GS|U-3515||2}}, which were commissioned into the [[Soviet Navy]] as {{ship|Soviet submarine|B-27||2}}, {{ship|Soviet submarine|B-28||2}}, ''B-29'', and {{ship|Soviet submarine|B-30||2}} (later ''B-100'') respectively. However, Western intelligence believed the Soviets had acquired several more Type XXI boats; a review by the [[United States Joint Intelligence Community Council|U.S. Joint Intelligence Committee]] for the [[Joint Chiefs of Staff]] during January 1948 estimated the Soviet Navy then had 15 Type XXIs operational, could complete construction of 6 more within 2 months, and could build another 39 within a year and a half from prefabricated sections, since several factories producing Type XXI components and the assembly yard at Danzig had been captured by the Soviets at the end of World War II. ''U-3538'' — ''U-3557'' (respectively ''TS-5'' – ''TS-19'' and ''TS-32'' – ''TS-38'') remained incomplete at Danzig and were scrapped or sunk during 1947. The four boats assigned by Potsdam were used in trials and tests until 1955, then scuttled or used for weapon testing between 1958 and 1973. The Type XXI design formed the basis for several Soviet design projects, Projects 611, 613, 614, 633, and 644. These became the submarine classes known by their NATO codes as {{sclass2|Zulu|submarine|5}}, {{sclass2|Whiskey|submarine|5}} and {{sclass2|Romeo|submarine|5}} submarine classes.<ref>{{cite book | last = Polmar| first = Norman | author2 = Kenneth J. Moore | title = Cold War Submarines: The Design and Construction of U.S. and Soviet Submarines | publisher = Brassey's | year = 2004 | pages = 23–24 | isbn = 978-1-57488-594-1}}</ref>

===United Kingdom===
[[File:German submarine U 3008.jpg|thumb|right|German submarine ''U-3008'' in [[Portsmouth Naval Shipyard]], [[Kittery, Maine]]]]

{{GS|U-3017||2}} was commissioned into the [[Royal Navy]] as {{HMS|N41}}. It was used for tests until being scrapped during November 1949.

===United States===

The United States Navy acquired {{GS|U-2513||2}} and {{GS|U-3008||2}}, operating them both in the Atlantic Ocean. During November 1946 President [[Harry S. Truman]] visited ''U-2513''; the submarine dived to {{convert|440|ft|m}} with the President aboard.<ref>[https://news.google.com/newspapers?id=p1kbAAAAIBAJ&sjid=1EwEAAAAIBAJ&pg=3101,1930838&dq=truman+sub&hl=en "Truman Dives 440 Feet In German Sub"], ''The Pittsburgh Press'', November 21, 1946, p9</ref> ''U-2513'' was sunk as a target on 7 October 1951; ''U-3008'' was sold for scrap on 15 September 1955.

==Survivor==
[[File:U-Boot Typ XXI U-2540 ( Wilhelm Bauer ) (9447881765) b.jpg|thumb|''Wilhelm Bauer'' (''U-2540''), preserved as a floating museum ship at the [[German Maritime Museum]] in Bremerhaven (2013)]]

The only boat to survive intact is {{GS|Wilhelm Bauer||2}} (ex-''U-2540''), at the [[German Maritime Museum]] in Bremerhaven.<ref name="Hitler's U-boat Bases">''Hitler's U-boat Bases'' (2002), Jak P Mallmann Showell, Sutton Publishing {{ISBN|0-7509-2606-6}}</ref> Records indicate that this sub was scuttled by her crew in 1945, salvaged in 1957 and refurbished for use by the West German ''Bundesmarine'' until retirement in 1982. She was then modified to appear in wartime configuration for exhibition purposes.<ref>{{cite book|author=Gordon Williamson |url=https://books.google.com/books?id=94SICwAAQBAJ&q=u-boat+type+XXI+only+two+went+out+on+patrol&pg=PT61|title=Kriegsmarine U-boats 1939–45|publisher=841763640|date=2002 |isbn=9781780966618}}</ref>

==Notable wrecks==
The wrecks of several Type XXI boats are known to exist. During 1985, it was discovered that the partially scrapped remains of {{GS|U-2505||2}}, {{GS|U-3004||2}}, and {{GS|U-3506||2}} were still in the partially demolished "Elbe II" U-boat bunker in [[Hamburg]]. The bunker has since been filled in with gravel, although even that did not initially deter many souvenir hunters who measured the position of open hatches and dug down to them to allow the removal of artifacts.<ref name="Hitler's U-boat Bases" /> The wrecks now lie beneath a car park (parking lot), making them inaccessible.<ref>{{cite web | title = 3 Type XXI boats in the Elbe II in Hamburg | publisher = uboat.net | url = http://uboat.net/history/hamburg_elbe2.htm }}</ref>

{{GS|U-2513||2}} lies in {{convert|213|ft|m}} of water {{convert|70|nmi|km}} west of [[Key West]], Florida. The boat has been visited by divers, but the depth makes this very difficult and the site is considered suitable for only advanced divers. Four other boats lie off the coast of Northern Ireland, where they were sunk during 1946 as part of [[Operation Deadlight]]. Both {{GS|U-2511||2}} and {{GS|U-2506||2}} were found by nautical archaeologist [[Innes McCartney]] during his ''Operation Deadlight'' expeditions between 2001 and 2003.<ref>{{cite web | url = http://www.uboat.net/gallery/DivingE/ | title = Uboat.net Operation Deadlight dives 2001}}</ref><ref>{{cite web | url = http://www.uboat.net/gallery/DivingF/ | title = Uboat.net Operation Deadlight dives 2002}}</ref> Both were found to be in good condition. In April 2018 the wreck of {{GS|U-3523||2}} was found north of Skagen in Denmark.<ref>{{cite web|author1=Ritzau|author-link1=Ritzau|title=Rare wreckage of groundbreaking nazi submarines found in the Skagerrak|url=http://nyheder.tv2.dk/samfund/2018-04-13-sjaeldent-vrag-af-banebrydende-nazi-ubad-fundet-i-skagerrak|website=tv2.dk|access-date=13 April 2018|language=da|date=13 April 2018}}</ref>

==Influences==
The Type XXI design directly influenced advanced post-war submarines, the [[Greater Underwater Propulsion Power Program]] (GUPPY) improvements to the [[United States]] {{sclass|Gato|submarine|5}}, {{sclass|Balao|submarine|5}}, and {{sclass|Tench|submarine|5}}-class submarines,<ref>{{cite book |last=Friedman |first=Norman |title=U.S. Submarines Since 1945: An Illustrated Design History |pages=23–28, 35, 40–43 |publisher=[[United States Naval Institute]] |year=1994|location=[[Annapolis, Maryland]] |isbn=1-55750-260-9}}</ref> and the [[Soviet Union|Soviet]] submarine projects designated {{sclass2|Whiskey|submarine|5}}, {{sclass2|Zulu|submarine|5}},<ref>Fitzsimons, Bernard, general editor. ''The Encyclopedia of 20th Century Weapons and Warfare'' (London: Phoebus Publishing Company, 1978), Volume 24, p.2594, "'Whiskey'", and p.2620, "'Zulu'".</ref> and {{sclass2|Romeo|submarine|5}} [[NATO reporting name|by NATO]]. The Chinese-built Romeo-class submarines, and the subsequent {{sclass2|Ming|submarine|4}}, were based on Soviet blueprints.

==See also==
* [[List of Type XXI submarines]]
* [[British R-class submarine]]
* {{sclass|I-201|submarine|1}}

==Notes==
{{Reflist|35em}}

==References==
*{{cite book |last1=Blair |first1=Clay |title=Hitler's U-boat War: The Hunters 1939-1942 |date=2000 |publisher=Cassel & Co |location=London |isbn=0304352608}}
* {{cite book
|last=Breyer
|first=Siegfried
|title=German U-Boat Type XXI
|translator-last=Force
|translator-first=Ed
|publisher=Schiffer
|location=Atglen, PA
|year=1999
|isbn=978-0-7643-0787-4
}}
* Fitzsimons, Bernard, general editor. ''The Encyclopedia of 20th Century Weapons and Warfare'' (London: Phoebus Publishing Company, 1978), Volume 24, p.&nbsp;2594, "'Whiskey'", and p.&nbsp;2620, "'Zulu'".
* {{cite book
|last1=Gröner
|first1=Erich
|last2=Jung
|first2=Dieter
|last3=Maass
|first3=Martin
|translator-last1=Thomas
|translator-first1=Keith
|translator-last2=Magowan
|translator-first2=Rachel
|year=1991
|title=German Warships 1815–1945, U-boats and Mine Warfare Vessels
|volume=2
|location=London
|publisher=Conway Maritime Press
|isbn=978-0-85177-593-7
}}
* {{cite book | last = Kohl | first = Fritz | author2 = Eberhard Rossler | title = The Type XXI U-boat | publisher = Conway Maritime | year = 1991 | isbn = 978-1-55750-829-4 }}

==External links==
{{Commons category|Type XXI submarines}}
* [http://ipmsstockholm.org/magazine/2003/11/detail_uboot_xxi.htm U-Boot Type XXI in Detail] {{Webarchive|url=https://web.archive.org/web/20070927034240/http://ipmsstockholm.org/magazine/2003/11/detail_uboot_xxi.htm |date=2007-09-27 }} with photos.
* {{cite web
 |url=http://www.uboat.net/types/xxi.htm
 |title=Type XXI
 |last=Helgason
 |first=Guðmundur
 |website=German U-boats of WWII - uboat.net
 |access-date= 20 April 2015
}}
* [http://www.uboataces.com/uboat-type-xxi.shtml Type XXI] on www.uboataces.com

{{German Type XXI submarines}}
{{Uboat}}
{{WWII German ships}}
{{Authority control}}

{{DEFAULTSORT:Type 021 submarines}}
[[Category:Type XXI submarines| ]]
[[Category:Submarine classes]]
[[Category:World War II submarines of Germany]]