SM U-11 or U-XI was a in 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 World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

. She was originally a German

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 Type UB I

German type UB I submarine

The Type UB I was a class of small coastal submarines built in Germany at the beginning of the First World War. Twenty boats were constructed, most of which went into service with the German Imperial Navy. Boats of this design were also operated by the Austro-Hungarian Navy and the Bulgarian...

 submarine commissioned

Ship commissioning

Ship commissioning is the act or ceremony of placing a ship in active service, and may be regarded as a particular application of the general concepts and practices of project commissioning. The term is most commonly applied to the placing of a warship in active duty with its country's military...

 into the German Imperial Navy  as SM UB-15.

SM UB-15 was constructed in Germany and shipped by rail to Pola

Pula

Pula is the largest city in Istria County, Croatia, situated at the southern tip of the Istria peninsula, with a population of 62,080 .Like the rest of the region, it is known for its mild climate, smooth sea, and unspoiled nature. The city has a long tradition of winemaking, fishing,...

, where she was assembled and launched. She was commissioned into the German Imperial Navy in April and sank an Italian 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...

 in June. The boat was handed over to 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 commissioned as SM U-11 on 14 June. In early 1916, U-11 fired on a British submarine, but missed. After the end of the war, U-11 was handed over to Italy as a war reparation and scrapped at Pola by 1920.

Design and construction

U-11 was a small coastal submarine that displaced 125.5 long tons (127.5 t) surfaced and 140.25 long tons (142.5 t) submerged. She featured a single shaft, a single 60 bhp Körting 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 120 shp electric motor for submerged travel. U-11 was capable of up to 6.5 knots while surfaced and 5.5 knots while submerged at a diving depth of up to 50 metres (164 ft). She was designed for a crew of 17 officers and men.

U-11 was equipped with two 45 cm (17.7 in) torpedo tubes located in the front and carried a complement of two torpedoes. German Type UB I submarines were additionally equipped with a 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....

, but it is not clear from sources if U-11 a former German boat was fitted with one, or if it was, retained it in Austro-Hungarian service. In October 1916, U-11s armament was supplemented with a 66 mm/18 (2.6 in) gun.

UB-15 was laid down on 9 November 1914 at AG Weser

AG Weser

Aktien-Gesellschaft Weser was one of the great German shipbuilding companies, located at the Weser River in Bremen. Founded in 1873 it was finally closed in 1983. Altogether, AG Weser built about 1400 ships of different types, including many war ships...

 in Bremen

Bremen

The City Municipality of Bremen is a Hanseatic city in northwestern Germany. A commercial and industrial city with a major port on the river Weser, Bremen is part of the Bremen-Oldenburg metropolitan area . Bremen is the second most populous city in North Germany and tenth in Germany.Bremen is...

. The submarine was shipped by rail in sections to Pola

Pula

Pula is the largest city in Istria County, Croatia, situated at the southern tip of the Istria peninsula, with a population of 62,080 .Like the rest of the region, it is known for its mild climate, smooth sea, and unspoiled nature. The city has a long tradition of winemaking, fishing,...

, where the sections were riveted together. There is no known surviving record of how long it took for UB-15's sections to be assembled. However, a similar ship (UB-3) was built in two weeks.

Operational history

SM UB-15 was commissioned into the German Imperial Navy under the command of Oberleutnant zur See Heino von Heimburg

Heino von Heimburg

Heino von Heimburg was a German U-boat commander in the Kaiserliche Marine during World War I and served also as Vice Admiral in the Kriegsmarine during World War II.-World War I:...

 on 11 April. An Austro-Hungarian Navy officer was assigned to the boat for piloting and training purposes. On 10 June, UB-15 sank the Italian submarine Medusa for a loss of 245 tons off Porto di Piave Vecchia in the Northern Adriatic.Sources differ as to whether the U-boat was under German or Austro-Hungarian ownership when she sank the Medusa. See Stern, p. 193. Like all Type UB I and U-10 class submarines, UB-15 was equipped with compensating tanks designed to flood and offset the loss of one of the 1700 pounds (771.1 kg) C/06 torpedoes. However, they did not always function correctly; when firing from periscope depth the boat could broach after firing or, if too much weight was taken on, plunge to the depths. When UB-15 torpedoed and sank Medusa, the tank failed to properly compensate, forcing all of the crewmen to run to the stern to offset the trim imbalance and prevent the ship from sinking.

On 14 June, UB-15 was handed over to the Austro-Hungarian Navy and commissioned as U-11 under the command of Linienschiffsleutnant Lüdwig Eberhardt. U-11 retained its German crew until 18 June 1916, when they were replaced by an all Austro-Hungarian one. In early 1916, U-11 unsuccessfully attacked the British submarine in the Gulf of Fiume. U-11 sank no ships in her Austro-Hungarian service, and was handed over to Italy as a war reparation and scrapped at Pola by 1920.