SM ''U-73'' was one of 329

submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...

s serving in the

Imperial German Navy The Imperial German Navy or the Imperial Navy () was the navy of the German Empire, which existed between 1871 and 1919. It grew out of the small Prussian Navy (from 1867 the North German Federal Navy), which was mainly for coast defence. Wilhel ...

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

. She engaged in the commerce war as part of the

First Battle of the Atlantic The Atlantic U-boat campaign of World War I (sometimes called the "First Battle of the Atlantic", in reference to the World War II campaign of that name) was the prolonged naval conflict between German submarines and the Allied navies in Atla ...

. ''U-73'' has the distinction of being responsible for planting the underwater mine that later led to the sinking of the largest ship sunk during World War I, the 48,158 tons

hospital ship A hospital ship is a ship designated for primary function as a floating medical treatment facility or hospital. Most are operated by the military forces (mostly navies) of various countries, as they are intended to be used in or near war zones. ...

''Britannic''.

Operations

After completion at Danzig in November 1915, ''U-73'' was commissioned by ''

Kapitänleutnant ''Kapitänleutnant'', short: KptLt/in lists: KL, ( en, captain lieutenant) is an officer grade of the captains' military hierarchy group () of the German Bundeswehr. The rank is rated OF-2 in NATO, and equivalent to Hauptmann in the Heer and ...

'' Gustav Sieß. She joined the Kiel School, where she remained until February 1916, conducting trials and crew training. She then left for the North Sea and was attached to the 1st Half Flotilla. Her activities were monitored throughout the war by

Room 40 Room 40, also known as 40 O.B. (old building; officially part of NID25), was the cryptanalysis section of the British Admiralty during the First World War. The group, which was formed in October 1914, began when Rear-Admiral Henry Oliver, the ...

, and most of her recorded movements are based on that information. Her first operational cruise began 1 April 1916, when she left

Heligoland Bight The Heligoland Bight, also known as Helgoland Bight, (german: Helgoländer Bucht) is a bay which forms the southern part of the German Bight, itself a bay of the North Sea, located at the mouth of the Elbe river. The Heligoland Bight extends fro ...

, bound for the

Mediterranean The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the e ...

by way of the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

. En route, she attacked one steamer in the

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

and laid

mine Mine, mines, miners or mining may refer to: Extraction or digging * Miner, a person engaged in mining or digging *Mining, extraction of mineral resources from the ground through a mine Grammar *Mine, a first-person English possessive pronoun ...

s off Lisbon and Malta. On 27 April 1916 she laid a minefield of 22 mines outside the

Grand Harbour The Grand Harbour ( mt, il-Port il-Kbir; it, Porto Grande), also known as the Port of Valletta, is a natural harbour on the island of Malta. It has been substantially modified over the years with extensive docks (Malta Dockyard), wharves, and ...

Valletta Valletta (, mt, il-Belt Valletta, ) is an Local councils of Malta, administrative unit and capital city, capital of Malta. Located on the Malta (island), main island, between Marsamxett Harbour to the west and the Grand Harbour to the east, i ...

in which four ships were sunk: the battleship ; the sloop ; HMT Crownsin, sunk 4 May 1916 with the loss of 11 men; and the yacht HMY ''Aegusa''. On arriving in

Cattaro Kotor (Montenegrin Cyrillic: Котор, ), historically known as Cattaro (from Italian: ), is a coastal town in Montenegro. It is located in a secluded part of the Bay of Kotor. The city has a population of 13,510 and is the administrative c ...

on about 1 May (the date is uncertain), ''U-73'' joined the Pola-Cattaro Flotilla. The minelaying cruises of ''U-73'' in the Mediterranean cannot be reconstructed. The battleship HMS ''Russell'' hit two of the mines and sank. On 7 October 1916 she is reported to have left

Pola Pola or POLA may refer to: People *House of Pola, an Italian noble family *Pola Alonso (1923–2004), Argentine actress *Pola Brändle (born 1980), German artist and photographer *Pola Gauguin (1883–1961), Danish painter *Pola Gojawiczyńska (18 ...

Croatia , image_flag = Flag of Croatia.svg , image_coat = Coat of arms of Croatia.svg , anthem = "Lijepa naša domovino"("Our Beautiful Homeland") , image_map = , map_caption = , capit ...

, and the French put down to her the mine sunk off Cape Male on 12 October, as well as a minefield in the Gulf of Salonika, and mines in the Gulf of Athens on which two Greek ships were blown up. It seems certain ''U-73'', still commanded by Sieß, laid the mine by which the hospital ship HMHS ''Britannic'' (currently the largest passenger ship resting on the seafloor and the largest ship sunk during World War I) was lost, only one hour after ''U-73'' laid the mine. It is possible the hospital ship HMHS ''Braemar Castle'' was also damaged by one of her mines. ''U-73'' suffered from constant machinery trouble in common with her class. At the end of October 1918, now in the hands of Kptlt. Fritz Saupe, she was

scuttled Scuttling is the deliberate sinking of a ship. Scuttling may be performed to dispose of an abandoned, old, or captured vessel; to prevent the vessel from becoming a navigation hazard; as an act of self-destruction to prevent the ship from being ...

at Pola in Croatia.

Summary of raiding history

References

Notes

Citations

Bibliography

* {{DEFAULTSORT:U0073 World War I submarines of Germany North Sea operations of World War I Mediterranean naval operations of World War I 1915 ships U-boats commissioned in 1916 Ships built in Kiel U-boats scuttled in 1918 Maritime incidents in 1918 German Type UE I submarines