SM U-15 or U-XV was a 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...

 of 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...

. U-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 in April 1915. She was 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...

 in October 1915. U-15 was the most successful boat of the U-10 class, sinking six ships totaling more than . The boat survived the war and was handed over to Italy as a war reparation and scrapped in 1920.

Design and construction

U-15 was constructed 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...

 for 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....

 and then 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. Though there is no specific mention of how long it took for U-15s sections to be assembled, a sister boat, the German Type UB I submarine

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...

 UB-3, shipped to Pola from Germany in mid-April 1915, was assembled in about two weeks.The Austro-Hungarian and the German 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...

 were virtually identical. U-15 was launched in April.

U-15 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 Daimler 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-15 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-15 was equipped with two 45 cm (17.7 in) torpedo tubes located in the front and carried a complement of two torpedoes. In October 1916, U-15s armament was supplemented with a 37 mm/23 (1.5 in) quick-firing

Quick-firing gun

A quick-firing gun is an artillery piece, typically a gun or howitzer, which has several characteristics which taken together mean the weapon can fire at a fast rate...

 (QF) gun. This gun was replaced by a 47 mm/23 (1.9 in) QF gun in November 1917.

Operational history

SM U-15 was commissioned into the Austro-Hungarian Navy on 6 October under the command of Linienschiffsleutnant Friedrich Schlosser. On 28 November, Linienschiffsleutnant Friedrich Fähndrich was assigned to the first of two stints in command of the boat. On 18 December, Fähndrich and U-15 attacked and sank two Albania

Albania

Albania , officially known as the Republic of Albania , is a country in Southeastern Europe, in the Balkans region. It is bordered by Montenegro to the northwest, Kosovo to the northeast, the Republic of Macedonia to the east and Greece to the south and southeast. It has a coast on the Adriatic Sea...

n sailing vessels near Lezhë

Lezhë

Lezhë is a city in northwest Albania, in the district and county with the same name. It is located at and has a population of about 27,500...

. The Erzen, of , and the Figlio Preligiona, of , were both sunk at position 41°47′N 19°31′E.

After being relieved by Linienschiffsleutnant Franz Rzemenowsky von Trautenegg from late March to early May 1916, Fähndrich resumed command on 10 May. One week later, on 17 May, U-15 torpedoed and sank the Italian steamer in the Adriatic some 18 nautical miles (33.3 km) east of Brindisi

Brindisi

Brindisi is a city in the Apulia region of Italy, the capital of the province of Brindisi, off the coast of the Adriatic Sea.Historically, the city has played an important role in commerce and culture, due to its position on the Italian Peninsula and its natural port on the Adriatic Sea. The city...

.Stura, launched in 1883, had sailed in passenger duty for Navigazione Generale Italiana

Navigazione Generale Italiana

Navigazione Generale Italiana was an Italian shipping company formed in 1881 by the merger of I & V. Florio of Palermo and Raffaele Rubattino of Genoa...

 between the Mediterranean and New York before the war. See: Immigration Information Bureau, pp. 8–9, 16, 23.

The following month, Fähndrich and the crew of U-15 scored their second double kill when they sank the Italian auxiliary cruiser  and the French destroyer

Destroyer

In naval terminology, a destroyer is a fast and maneuverable yet long-endurance warship intended to escort larger vessels in a fleet, convoy or battle group and defend them against smaller, powerful, short-range attackers. Destroyers, originally called torpedo-boat destroyers in 1892, evolved from...

 Fourche . While about 20 nautical miles (37 km) east of Otranto

Otranto

Otranto is a town and comune in the province of Lecce , in a fertile region once famous for its breed of horses.It is located on the east coast of the Salento peninsula. The Strait of Otranto, to which the city gives its name, connects the Adriatic Sea with the Ionian Sea and Italy with Albania...

 on 23 June, U-15 torpedoed and sank Cittá di Messina. The escorting destroyer Fourche began a depth charge

Depth charge

A depth charge is an anti-submarine warfare weapon intended to destroy or cripple a target submarine by the shock of exploding near it. Most use explosives and a fuze set to go off at a preselected depth in the ocean. Depth charges can be dropped by either surface ships, patrol aircraft, or from...

attack on U-15 and assumed success when an oil slick appeared on the surface. After the captain of Fourche turned his attentions to the rescue Cittá di Messinas survivors, U-15 launched a single torpedo that struck Fourche amidships and sank her.

On 25 October, U-15, back under the command of von Trautenegg, sank the Italian steamer , a sister ship to Stura (sunk by U-15 in May). Polcevera was the last ship sunk by U-15.

From October 1916 to the end of the fighting in November 1918, U-15s activities are unknown. U-15 was at Pola at the end of the war when Austria-Hungary handed her over to Italy. U-15 was scrapped at Pola by 1920.