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SM U-20 (Austria-Hungary)

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The design for U-20 was based on the Havmanden class of the Royal Danish Navy (Havmanden pictured)
The design for U-20 was based on the Havmanden class of the Royal Danish Navy (Havmanden pictured)
Name: SM U-20
Ordered: 27 March 1915[1]
Builder: Pola Navy Yard, Pola[2]
Laid down: 29 September 1915[3]
Launched: 18 September 1916[2]
Commissioned: 20 October 1917[3]
Fate: sunk by Italian submarine F-12, 4 July 1918, raised and partially scrapped in 1962, remaining parts donated to museum[4]
Service record
  • Klemens Ritter von Bezard (May 1916 – April 1917)[5]
  • Franz Rzemenowsky von Trautenegg (July – November 1917)
  • Hermann Rigele (November 1917 – March 1918)
  • Ludwig Müller (March – July 1918)
Victories: None[5]
General characteristics
Class and type: U-20-class submarine
  • 173 t, surfaced
  • 210 t, submerged[2]
Length: 127 ft 2 in (38.76 m)[2]
Beam: 13 ft (4.0 m)[2]
Draft: 9 ft (2.7 m)[2]
  • 12 knots (22 km/h) surfaced
  • 9 knots (17 km/h) submerged[2]
  • 1,400 nautical miles (2,600 km) at 10 knots (19 km/h) surfaced[6]
  • 23 nautical miles (43 km) at 8 knots (15 km/h) submerged
Complement: 18[2]

SM U-20 or U-XX was the lead boat of the U-20 class of submarines or U-boats built for and operated by the Austro-Hungarian Navy (German: Kaiserliche und Königliche Kriegsmarine or K.u.K. Kriegsmarine) during the First World War. The design for U-20 was based on submarines of the Royal Danish Navy's Havmanden class (three of which had been built in Austria-Hungary), and was largely obsolete by the beginning of the war.

U-20 was just over 127 feet (39 m) long and was armed with two bow torpedo tubes, a deck gun, and a machine gun. U-20 had no wartime successes and was sunk in early July 1918 by the Italian submarine F-12. The wreck of U-20 was located in 1962 and salvaged. A portion of her conning tower is on display in a military museum in Vienna.

Design and construction[edit]

When it became apparent to the Austro-Hungarian Navy that the First World War would not be a short war,[1] they moved to bolster their U-boat fleet by seizing the plans for Denmark's Havmanden class submarines,[7] three of which had been built at Whitehead & Co. in Fiume.[6] Although the Austro-Hungarian Navy was not happy with the design, which was largely obsolete,[8][9] it was the only design for which plans were available and which could be begun immediately in domestic shipyards.[9] The Austro-Hungarian Navy unenthusiastically placed orders for U-20 and her three sister boats on 27 March 1915.[1]

U-20 was one of two boats of the class to be built at the Pola Navy Yard.[7] Due to demands by the Hungarian government,[1] subcontracts for the class were divided between Hungarian and Austrian firms,[2] but this politically expedient solution worsened technical problems with the design and resulted in numerous modifications and delays for the class in general.[7]

U-20 was an ocean-going submarine that displaced 173 tonnes (191 short tons) surfaced and 210 tonnes (231 short tons) submerged and was designed for a complement of 18. She was 127 feet 2 inches (38.76 m) long with a beam of 13 feet (4.0 m) and a draft of 9 feet (2.7 m). For propulsion, she featured a single propeller shaft, a single 450 bhp (340 kW) diesel engine for surface running, and a single 160 shp (120 kW) electric motor for submerged travel.[2] She was capable of 12 knots (22 km/h) while surfaced and 9 knots (17 km/h) while submerged. Although there is no specific notation of a range for U-20, the Havmanden class, upon which the U-20 class was based, had a range of 1,400 nautical miles (2,600 km) at 10 knots (19 km/h), surfaced, and 23 nautical miles (43 km) at 8 knots (15 km/h) submerged.[6]

U-20 was armed with two 45 cm (17.7 in) torpedo tubes located in the front and carried a complement of two torpedoes. She was also equipped with a 66 mm (2.6 in) deck gun and an 8 mm (0.31 in) machine gun.[2]

U-20 was laid down on 29 September 1915,[3] six months after she was ordered,[1] and was launched on 18 September 1916.[2]

Service career[edit]

The conning tower of U-20 on display at the Heeresgeschichtliches Museum in Vienna
Details of U-20 conning tower.

Upon completion, U-20 began diving trials. On her 15 March 1917 trial, she was accidentally rammed by Admiral Spaun in the Fasana Channel. The collision with the Austro-Hungarian light cruiser twisted U-20's periscope, extensively damaged the conning tower, and knocked off her deck gun. After seven months of reconstruction, U-20 was commissioned into the Austro-Hungarian Navy on 20 October.[3]

After initially operating out of Pola, U-20 was transferred to Trieste in February 1918. Over the next three months, the U-boat patrolled in the northern Adriatic between the Tagliamento estuary and Venice. U-20 had an encounter with an enemy submarine on 7 April but was not able to successfully launch an attack.[3] On 3 July, Linienschiffsleutnant Ludwig Müller sailed U-20 out from Trieste for the Gulf of Venice. A day later, U-20 was spotted by the Italian submarine F-12, which was on patrol in the northern Adriatic. F-12 initially pursued U-20 underwater, and then on the surface. At a range of 650 yards (590 m), F-12 torpedoed U-20 at position 45°29′N 13°05′E / 45.483°N 13.083°E / 45.483; 13.083 (SM U-20), sinking her with all hands. There was no wreckage on the surface, only an oil slick.[4][Note 1] Like all of her sister boats,[7] U-20 had no wartime successes.[5]

In mid 1962, the wreck of U-20 was discovered in the northern Adriatic. Italian salvage crews raised the boat's rear portion on 22 July and her front section on 21 November.[4] The conning tower and a small midships section of U-20 were donated to the Heeresgeschichtliches Museum in Vienna, where they are on display, while the rest of the boat was scrapped.[7] The remains of the crewmen were buried on the grounds of the Theresian Military Academy at Wiener Neustadt.[10]


  1. ^ Grant (p. 163) gives the date of U-20's loss as 4 July 1918. Compton-Hall (p. 235) reports it on 9 July, while Baumgartner and Sieche report it on 6 July.
    For Baumgartner and Sieche, see excerpt here (reprinted and translated into English by Sieche). Retrieved 29 November 2008.


  1. ^ a b c d e Halpern, p. 382.
  2. ^ a b c d e f g h i j k l m n Gardiner, p. 343.
  3. ^ a b c d e "Tengeralattjárók" (pdf) (in Hungarian). Imperial and Royal Navy Association. p. 20. Retrieved 2 February 2009.
  4. ^ a b c Grant, p. 163.
  5. ^ a b c Helgason, Guðmundur. "WWI U-boats: KUK U20". German and Austrian U-boats of World War I - Kaiserliche Marine - Retrieved 29 November 2008.
  6. ^ a b c Gardiner, p. 354.
  7. ^ a b c d e Gardiner, p. 344.
  8. ^ Halpern, p. 383.
  9. ^ a b Gardiner, p. 341.
  10. ^ Baumgartner and Sieche, as excerpted here (reprinted and translated into English by Sieche). Retrieved 17 November 2008.