SM U-31 (Austria-Hungary) - AbsoluteAstronomy.com

SM U-31 or U-XXXI was a U-27 class

U-27 class submarine (Austria-Hungary)

The U-27 class was a class of eight submarines or U-boats built for and operated by the Austro-Hungarian Navy during World War I. The class was based upon the German Type UB II design of the German Imperial Navy and was constructed under license in Austria-Hungary.After the Austro-Hungarian Navy...

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...

or 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...

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....

. U-31, built by the Hungarian firm of Ganz Danubius at Fiume, was launched in March 1917 and commissioned in April.

U-31 had a single hull

Submarine hull

The term light hull is used to describe the outer hull of a submarine, which houses the pressure hull, providing hydrodynamically efficient shape, but not holding pressure difference...

and was just over 121 feet (36.9 m) in length. She displaced

Displacement (ship)

A ship's displacement is its weight at any given time, generally expressed in metric tons or long tons. The term is often used to mean the ship's weight when it is loaded to its maximum capacity. A number of synonymous terms exist for this maximum weight, such as loaded displacement, full load...

nearly 265 metric tons (261 LT) when surfaced and over 300 metric tons (295 LT) when submerged. Her two 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...

s moved her at up to 9 knots on the surface, while her twin electric motor

Electric motor

An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...

s propelled her at up to 7.5 knots while underwater. She was armed with two bow torpedo tube

Torpedo tube

A torpedo tube is a device for launching torpedoes. There are two main types of torpedo tube: underwater tubes fitted to submarines and some surface ships, and deck-mounted units installed aboard surface vessels...

s and could carry a load of up to four torpedoes. She was also equipped with a 75 mm (3 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 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....

.

In October 1917, U-31 sank while in port at Porto Bergudi and was out of service through April 1918 while she was raised and repaired. During her service career, U-31 sank two ships and damaged one warship, sending a combined tonnage of to the bottom. U-31 was at Cattaro at war's end and was awarded to France as war reparation in 1920, towed to Bizerta and scrapped there.

Design and construction

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...

's U-boat fleet was largely obsolete at the outbreak of 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...

. 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....

satisfied its most urgent needs by purchasing five 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...

submarines that comprised the from Germany, by raising and recommissioning the sunken French submarine Curie

French submarine Curie (Q 87)

SM U-14 or U-XIV was a U-boat or submarine of the Austro-Hungarian Navy during the First World War. She was launched in 1912 as the French Curie , but captured and rebuilt for service in the Austro-Hungarian Navy...

as ,Curie

French submarine Curie (Q 87)

had been caught in an anti-submarine net

Anti-submarine net

An anti-submarine net is a device placed across the mouth of a harbour or a strait for protection against submarines.-Examples of anti-submarine nets:*Lake Macquarie anti-submarine boom*Indicator net*Naval operations in the Dardanelles Campaign...

while trying to enter the harbor at 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,...

on 20 December 1914. See: Gardiner, p. 343. and by building four submarines of the that were based on the 1911 Danish 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...

.The plans for the Danish Havmanden class submarines

Havmanden class submarine (1911)

, three of which were built in Austria-Hungary, were seized from Whitehead & Co. in Fiume. See: Gardiner, pp. 344, 354.

After these steps alleviated their most urgent needs, the Austro-Hungarian Navy selected the German Type UB II

German type UB II submarine

The UB II type submarine was a class of U-boat built during World War I by the Kaiserliche Marine. They were enlarged from the preceding type UB I and were more effective vessels. The boats were a single hull design with a 50 metre maximum diving depth and a 30-45 second diving time...

design for its newest submarines in mid 1915. The Germans were reluctant to allocate any of their wartime resources to Austro-Hungarian construction, but were willing to sell plans for up to six of the UB II boats to be constructed under license in Austria-Hungary. The Austria-Hungarian Navy agreed to the proposal and purchased the plans from 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...

of 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...

.

U-31 displaced 264 metric tons (259.8 LT) surfaced and 301 metric tons (296.2 LT) submerged. She had a single hull

Submarine hull

The term light hull is used to describe the outer hull of a submarine, which houses the pressure hull, providing hydrodynamically efficient shape, but not holding pressure difference...

with saddle tank

Saddle tank (submarine)

Saddle tanks are a type of ballast tank configuration fitted to mid-era submarines, those of World War II.Saddle tanks are fitted in pairs external to the pressure hull, one on each side, in a similar manner to that of a horse's saddle-bags, the positioning of which they resemble in appearance.-...

s, and was 121 in 1 in (36.91 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 14 in 4 in (4.37 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 12 in 2 in (3.71 m). For propulsion, she had two shafts, twin 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...

s of 270 bhp for surface running, and twin electric motor

Electric motor

An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...

s of 280 shp for submerged travel. She was capable of 9 knots while surfaced and 7.5 knots while submerged. Although there is no specific notation of a range for U-31 in Conway's All the World's Fighting Ships, 1906–1921, the German UB II boats, upon which the U-27 class was based, had a range of over 6000 nautical miles (11,112 km) at 5 knots surfaced, and 45 nautical miles (83.3 km) at 4 knots submerged. U-27-class boats were designed for a crew of 23–24.

U-31 was armed with two 45 cm (17.7 in) bow torpedo tube

Torpedo tube

s and could carry a complement of four torpedoes. She was also equipped with a 75 mm/26 (3.0 in) deck gun

Deck gun

and an 8 mm (0.31496062992126 in) machine gun

Machine gun

.

After intricate political negotiations to allocate production of the class between Austrian and Hungarian firms, U-27 was ordered from Ganz Danubius on 12 October 1915. She was laid down on 4 July 1916 at Fiume and launched on 20 March 1917.

Service career

After undergoing trials at Fiume during March, U-31 made a training voyage to Brioni in April. On 24 April 1917, SM U-31 was commissioned into the Austro-Hungarian Navy under the command of Linienschiffsleutnant Franz Nejebsy. Nejebsy, a 32-year-old native of Teplitz-Schönau, Bohemia

Bohemia

Bohemia is a historical region in central Europe, occupying the western two-thirds of the traditional Czech Lands. It is located in the contemporary Czech Republic with its capital in Prague...

(present-day Czech Republic

Czech Republic

The Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest....

), had previously served two stints as commander of .

U-31 departed from Pola

Pula

on 29 May to patrol along the Adriatic coast of Italy and returned on 5 June. U-31 departed for a patrol in the Mediterranean on 19 June. After a problem with a pump required a stop at Brioni, the U-boat continued on. Nejebsy launched a torpedo attack on an armed yacht

Armed yacht

An armed yacht was a yacht that was armed with weapons and was typically in the service of a navy. Their speed and maneuverability made them useful as patrol vessels. In the United States Navy armed yachts were typically private yachts expropriated for government use in times of war. Armed yachts...

west of Strovathi on 25 June, but the torpedoes missed their mark. U-31 ended her patrol at Cattaro after ventilation problems kept the temperature in the engine room from falling below 45 °C (113 °F).

After a month of repairs at Cattaro, U-31 headed out on another patrol on 6 August. On each of the next two days the U-boat had to crash dive

Crash dive

A crash dive is a maneuver performed by a submarine to submerge as quickly as possible to avoid attack. Crash diving from the surface to avoid attack has been largely rendered obsolete with the advent of nuclear-powered submarines as they operate constantly submerged and are unlikely to be found on...

to avoid bombing attacks by French airplanes, the second day's attack damaging the boat slightly. On 10 August, Nejebsy and U-31 scored their first kill with the sinking of am Italian cargo ship

Cargo ship

A cargo ship or freighter is any sort of ship or vessel that carries cargo, goods, and materials from one port to another. Thousands of cargo carriers ply the world's seas and oceans each year; they handle the bulk of international trade...

. The 4,021-ton Lealta was carrying ammunition from Syracuse to Malta

Malta

Malta , officially known as the Republic of Malta , is a Southern European country consisting of an archipelago situated in the centre of the Mediterranean, south of Sicily, east of Tunisia and north of Libya, with Gibraltar to the west and Alexandria to the east.Malta covers just over in...

when U-31 intercepted her in the Ionian Sea

Ionian Sea

The Ionian Sea , is an arm of the Mediterranean Sea, south of the Adriatic Sea. It is bounded by southern Italy including Calabria, Sicily and the Salento peninsula to the west, southern Albania to the north, and a large number of Greek islands, including Corfu, Zante, Kephalonia, Ithaka, and...

east of Malta. An escorting 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...

dropped a pattern of ten 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...

s over U-31. The following day, Nejebsy was maneuvering U-31 into position to attack a convoy when the U-boat was rammed from behind by a destroyer. U-31s 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....

was hit and twisted by the impact, forcing Nejebsy to end his attack and U-31s patrol. On the way back to Cattaro, U-31 was attacked by an aircraft in the Straits of Otranto, but reached the safety of the port on 15 August.

U-31 was assigned to patrol the Austro-Hungarian and 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 coasts over the next six weeks. She headed to Fiume via Spalato on 16 October, reaching there three days later. On 26 October U-31 sank from an unknown cause in the harbor at Porto Bergudi. When raised from her resting depth of 8 metres (26.2 ft) the next day, one crewman was found alive inside the boat. U-31 was taken first to the Danubius shipyard at nearby Fiume, and, later, on to Pola for repairs and trials.

In January, while U-31s repairs were still ongoing, Nejebsy was reassigned, leaving the U-boat without a commander for the next three months. On 11 March Linienschiffsleutnant Hermann Rigele was transferred from the helm of to assume command of U-31. Rigele, who had been born in Sarajevo

Sarajevo

Sarajevo |Bosnia]], surrounded by the Dinaric Alps and situated along the Miljacka River in the heart of Southeastern Europe and the Balkans....

, was 26 years old and had also been in command of and, before that, at age 25.Rigele went on to command two German U-boats in the Second World War

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

, and , both captured Dutch submarines. See: Rigele and U-31 departed Pola on 30 April for a three-day cruise to Cattaro via Sebenico. On 20 May, the boat left Cattaro for a Mediterranean patrol, but had to turn back with leaks after a day.

In June, the Austro-Hungarian Navy planned an assault on the Otranto Barrage

Otranto Barrage

The Otranto Barrage was an Allied naval blockade of the Otranto Straits between Brindisi in Italy and Corfu on the Albanian side of the Adriatic Sea in World War I. The blockade was intended to prevent the Austro-Hungarian Navy from escaping into the Mediterranean and threatening Allied operations...

, similar to a May 1917 action that evolved into the Battle of Otranto Straits. U-31 was deployed from Cattaro on 9 June in advance of the attack. One of the seven separate groups participating in the attack—dreadnoughts and —came under attack from Italian MAS torpedo boats in the early morning hours of 10 June. Szent István was hit and sank just after 06:00, and the entire operation was called off. U-31 returned to Cattaro on 12 June.

On 16 June, Rigele and U-31 again set out for a Mediterranean patrol, but had to immediately return with clutch problems. Two days later, the U-boat set out again for the Mediterranean. The next day, 19 June, Rigele had to take the boat to a depth of 40 metres (131.2 ft) to avoid a depth charge attack. On 7 July, Rigele stopped the Italian sailing vessel Giuseppino Padre and, using explosive charges, sank the 67-ton ship. U-31 ended her patrol at Cattaro on 10 July. Over the next two months, the submarine operated in the Adriatic out of Cattaro and Pola, patrolling off Durazzo and the Albania

Albania

n coast.

After the Armistice with Bulgaria on 29 September ended Bulgaria's participation in the war, Durazzo gained importance to the remaining Central Powers

Central Powers

The Central Powers were one of the two warring factions in World War I , composed of the German Empire, the Austro-Hungarian Empire, the Ottoman Empire, and the Kingdom of Bulgaria...

as the main port for supplying their forces fighting in the Balkans

Balkans

The Balkans is a geopolitical and cultural region of southeastern Europe...

. Anticipating this, the Allies put together a force to bombard Durazzo. While the second echelon of the attacking force got into position to shell the town, U-31 and sister boat , both patrolling off Durazzo, maneuvered to attack. Although U-29 was blocked by screening ships and experienced a heavy depth charge attack, U-31 was able to get in position to launch torpedoes at the British cruiser . One of them hit its mark and blew the stern off of Weymouth, killing four sailors in the process. The other British cruisers involved in the attack took the damaged Weymouth under tow and departed. United States Navy

United States Navy

The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

submarine chaser

Submarine chaser

A submarine chaser is a small and fast naval vessel specially intended for anti-submarine warfare. Although similar vessels were designed and used by many nations, this designation was most famously used by ships built by the United States of America...

s were involved in the depth charge attacks on U-29 and U-31 and erroneously claimed that they had sunk both of the submarines. U-31 was able to make her way back to Cattaro on 6 October.

Over the next three weeks, U-31 patrolled between Cattaro and Antivari, Montenegro

Montenegro

Montenegro Montenegrin: Crna Gora Црна Гора , meaning "Black Mountain") is a country located in Southeastern Europe. It has a coast on the Adriatic Sea to the south-west and is bordered by Croatia to the west, Bosnia and Herzegovina to the northwest, Serbia to the northeast and Albania to the...

. After her arrival back at Cattaro on 26 October, she remained there until she was awarded to France as a war reparation in 1920. U-31 was towed, along with sister boats U-29 and , from Cattaro for scrapping at Bizerta. In total, U-31 sank two ships with a combined tonnage of 4,088, and damaged one warship.

Ships sunk or damaged

Ships sunk or damaged by SM U-31
Name	Tonnage	Nationality
Lealta	4,021	Italian
Giuseppino Padre	67	Italian
Weymouth*	5,250	British
Sunk: Damaged: Total:	4,088 5,250 9,338

* damaged but not sunk

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