SM U-20 or U-XX was the lead boat

Lead ship

The lead ship or class leader is the first of a series or class of ships all constructed according to the same general design. The term is applicable military ships and larger civilian craft.-Overview:...

 of the of submarine

Submarine

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

s or U-boat

U-boat

U-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...

s built for and operated by the Austro-Hungarian Navy

Austro-Hungarian Navy

The Austro-Hungarian Navy was the naval force of Austria-Hungary. Its official name in German was Kaiserliche und Königliche Kriegsmarine , abbreviated as k.u.k. Kriegsmarine....

  during the First World War. The design for U-20 was based on submarines of the Royal Danish Navy

Royal Danish Navy

The Royal Danish Navy is the sea-based branch of the Danish Defence force. The RDN is mainly responsible for maritime defence and maintaining the sovereignty of Danish, Greenlandic and Faroese territorial waters...

's Havmanden class

Havmanden class submarine (1911)

The Havmanden class was a class of six submarines built for the Royal Danish Navy from 1911 to 1914. Also later known as the A class, the boats were designed by the Austro-Hungarian firm Whitehead & Co. of Fiume...

 (three of which had been built in Austria-Hungary

Austria-Hungary

Austria-Hungary , more formally known as the Kingdoms and Lands Represented in the Imperial Council and the Lands of the Holy Hungarian Crown of Saint Stephen, was a constitutional monarchic union between the crowns of the Austrian Empire and the Kingdom of Hungary in...

), and was largely obsolete by the beginning of the war.

U-20 was just over 127 feet (38.7 m) long and was armed with two bow torpedo tubes, a deck gun

Deck gun

A deck gun is a type of artillery cannon mounted on the deck of a ship or submarine.The deck gun was used as a defensive weapon against smaller boats or ships and in certain cases where torpedo use was limited. Typically a crew of three; gunner, loader, and layer, operated the gun, while others...

, and a machine gun

Machine gun

A machine gun is a fully automatic mounted or portable firearm, usually designed to fire rounds in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute....

. 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

Conning tower

A conning tower is a raised platform on a ship or submarine, often armored, from which an officer can con the vessel; i.e., give directions to the helmsman. It is usually located as high on the ship as practical, to give the conning team good visibility....

 is on display in a military museum in Vienna

Vienna

Vienna is the capital and largest city of the Republic of Austria and one of the nine states of Austria. Vienna is Austria's primary city, with a population of about 1.723 million , and is by far the largest city in Austria, as well as its cultural, economic, and political centre...

.

Design and construction

When it became apparent to the Austro-Hungarian Navy

Austro-Hungarian Navy

The Austro-Hungarian Navy was the naval force of Austria-Hungary. Its official name in German was Kaiserliche und Königliche Kriegsmarine , abbreviated as k.u.k. Kriegsmarine....

 that the First World War would not be a short war, they moved to bolster their U-boat fleet by seizing the plans for Denmark's Havmanden class submarines

Havmanden class submarine (1911)

The Havmanden class was a class of six submarines built for the Royal Danish Navy from 1911 to 1914. Also later known as the A class, the boats were designed by the Austro-Hungarian firm Whitehead & Co. of Fiume...

, three of which had been built at Whitehead & Co. in Fiume. Although the Austro-Hungarian Navy was not happy with the design, which was largely obsolete, it was the only design for which plans were available and which could be begun immediately in domestic shipyards. The Austro-Hungarian Navy unenthusiastically placed orders for U-20 and her three sister boats

Sister ship

A sister ship is a ship of the same class as, or of virtually identical design to, another ship. Such vessels share a near-identical hull and superstructure layout, similar displacement, and roughly comparable features and equipment...

 on 27 March 1915.

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

U-20 was an ocean-going submarine that displaced 173 tonnes (190.7 ST) surfaced and 210 tonnes (231 ST) submerged and was designed for a complement of 18. She was 127 in 2 in (38.76 m) long with a beam

Beam (nautical)

The beam of a ship is its width at the widest point. Generally speaking, the wider the beam of a ship , the more initial stability it has, at expense of reserve stability in the event of a capsize, where more energy is required to right the vessel from its inverted position...

 of 13 feet (4 m) and a draft

Draft (hull)

The draft of a ship's hull is the vertical distance between the waterline and the bottom of the hull , with the thickness of the hull included; in the case of not being included the draft outline would be obtained...

 of 9 feet (2.7 m). For propulsion, she featured a single propeller shaft, a single 450 bhp diesel engine

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

 for surface running, and a single 160 shp electric motor for submerged travel. She was capable of 12 knots while surfaced and 9 knots 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 1400 nautical miles (2,592.8 km) at 10 knots, surfaced, and 23 nautical miles (42.6 km) at 8 knots submerged.

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/26 (2.6 in) deck gun

Deck gun

A deck gun is a type of artillery cannon mounted on the deck of a ship or submarine.The deck gun was used as a defensive weapon against smaller boats or ships and in certain cases where torpedo use was limited. Typically a crew of three; gunner, loader, and layer, operated the gun, while others...

 and an 8 mm (0.31496062992126 in) machine gun

Machine gun

A machine gun is a fully automatic mounted or portable firearm, usually designed to fire rounds in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute....

.

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

Service career

Upon completion, U-20 began diving trials. On her 15 March 1917 trial, she was accidentally rammed by in the Fasana Channel. The collision with the Austro-Hungarian light cruiser

Light cruiser

A light cruiser is a type of small- or medium-sized warship. The term is a shortening of the phrase "light armored cruiser", describing a small ship that carried armor in the same way as an armored cruiser: a protective belt and deck...

 twisted U-20s periscope

Periscope

A periscope is an instrument for observation from a concealed position. In its simplest form it consists of a tube with mirrors at each end set parallel to each other at a 45-degree angle....

, extensively damaged the conning tower

Conning tower

A conning tower is a raised platform on a ship or submarine, often armored, from which an officer can con the vessel; i.e., give directions to the helmsman. It is usually located as high on the ship as practical, to give the conning team good visibility....

, and knocked off her deck gun. After seven months of reconstruction, U-20 was commissioned into the Austro-Hungarian Navy on 20 October.
After initially operating out of Pola, U-20 was transferred to Trieste

Trieste

Trieste is a city and seaport in northeastern Italy. It is situated towards the end of a narrow strip of land lying between the Adriatic Sea and Italy's border with Slovenia, which lies almost immediately south and east of the city...

 in February 1918. Over the next three months, the U-boat patrolled in the northern Adriatic  between the Tagliamento estuary and Venice

Venice

Venice is a city in northern Italy which is renowned for the beauty of its setting, its architecture and its artworks. It is the capital of the Veneto region...

. U-20 had an encounter with an enemy submarine on 7 April but was not able to successfully launch an attack.

On 3 July, Linienschiffsleutnant Ludwig Müller sailed U-20 out from Trieste for the Gulf of Venice

Gulf of Venice

The Gulf of Venice is a gulf that borders modern day Italy, Slovenia and Croatia, and is at the far north of the Adriatic Sea between the delta of the Po river in northern Italy and the Istria peninsula in Croatia.- Geography :...

. 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, F-12 torpedoed U-20 at position 45°29′N 13°05′E, sinking her with all hands. There was no wreckage on the surface, only an oil slick.Grant (p. 163) gives the date of U-20s 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. Like all of her sister boats, U-20 had no wartime successes.

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. The conning tower

Conning tower

A conning tower is a raised platform on a ship or submarine, often armored, from which an officer can con the vessel; i.e., give directions to the helmsman. It is usually located as high on the ship as practical, to give the conning team good visibility....

 and a small midships section of U-20 were donated to the Heeresgeschichtliches Museum

Heeresgeschichtliches Museum

The Heeresgeschichtliches Museum is a military history museum located in Vienna, Austria. It claims to be the oldest and largest purpose-built military history museum in the world...

 in Vienna

Vienna

Vienna is the capital and largest city of the Republic of Austria and one of the nine states of Austria. Vienna is Austria's primary city, with a population of about 1.723 million , and is by far the largest city in Austria, as well as its cultural, economic, and political centre...

, where they are on display, while the rest of the boat was scrapped. The remains of the crewmen were buried on the grounds of the Theresian Military Academy

Theresian Military Academy

The Theresian Military Academy is an academy, where the Austrian Armed Forces train their officers. The Academy is located in the castle of Wiener Neustadt in Lower Austria.- History :...

 at Wiener Neustadt

Wiener Neustadt

-Main sights:* The Late-Romanesque Dom, consecrated in 1279 and cathedral from 1469 to 1785. The choir and transept, in Gothic style, are from the 14th century. In the late 15th century 12 statues of the Apostles were added in the apse, while the bust of Cardinal Melchior Klesl is attributed to...

.