The Type UB I was a class of small coastal submarines (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 in Germany

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...

 at the beginning of the First World War

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...

. 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

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....

 (Kaiserliche und Königliche Kriegsmarine or K.u.K. Kriegsmarine) and the Bulgarian Navy

Bulgarian Navy

The Bulgarian Navy is the navy of Republic of Bulgaria and forms part of the Bulgarian Armed Forces. It has been largely overlooked in the reforms that Bulgaria had to go through in order to comply with NATO standards, mostly because of the great expense involved and the fact that naval assaults...

. The group is sometimes known as the UB-1 class after , the class leader. In the Austro-Hungarian Navy, it was called the .

Built to meet the need for small maneuverable submarines able to operate in the narrow, shallow seas off Flanders

Flanders

Flanders is the community of the Flemings but also one of the institutions in Belgium, and a geographical region located in parts of present-day Belgium, France and the Netherlands. "Flanders" can also refer to the northern part of Belgium that contains Brussels, Bruges, Ghent and Antwerp...

, the vessels were intended to be quickly constructed, then shipped by rail and assembled at their port of operation. The design effort began in mid-August 1914 and by mid-October the first 15 boats were ordered from two German shipyards. The German Imperial Navy subsequently ordered an additional pair of boats to replace two sold 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...

, who ordered a further three boats in April 1915. A total of twenty UB Is were built. Construction of the first boats for Germany began in early November 1914; all twenty were completed by October 1915.

Several of the first boats underwent trials in German home waters, but the rest were assembled and tested at either Antwerp or 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,...

. The German boats operated primarily in the Flanders, Baltic, and Constantinople Flotilla

Constantinople Flotilla

The Constantinople flotilla was an Imperial German Navy formation set up to prosecute the U-boat campaign against Allied shipping in the Mediterranean and the Black Sea in support of Germany’s ally, the Ottoman Empire...

s. The boats were about 92 feet (28 m) long and displaced 127 tonnes (125 LT) when surfaced and 142 tonnes (139.8 LT) while submerged. All had two bow

Bow (ship)

The bow is a nautical term that refers to the forward part of the hull of a ship or boat, the point that is most forward when the vessel is underway. Both of the adjectives fore and forward mean towards the 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 two torpedo

Torpedo

The modern torpedo is a self-propelled missile weapon with an explosive warhead, launched above or below the water surface, propelled underwater towards a target, and designed to detonate either on contact with it or in proximity to it.The term torpedo was originally employed for...

es, and were equipped with a deck-mounted 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 1918 four of the surviving German boats were converted into coastal minelayer

Minelayer

Minelaying is the act of deploying explosive mines. Historically this has been carried out by ships, submarines and aircraft. Additionally, since World War I the term minelayer refers specifically to a naval ship used for deploying naval mines...

s. Of the seventeen boats in German service, two were sold to Austria-Hungary, one was sold to Bulgaria

Bulgaria

Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...

, and nine were lost during the war. One of the five Austro-Hungarian boats was sunk and another mined and not repaired. The five surviving German boats, the four surviving Austro-Hungarian boats, and the Bulgarian boat were all turned over to the Allies

Allies of World War I

The Entente Powers were the countries at war with the Central Powers during World War I. The members of the Triple Entente were the United Kingdom, France, and the Russian Empire; Italy entered the war on their side in 1915...

 after the end of the war and were broken up

Ship breaking

Ship breaking or ship demolition is a type of ship disposal involving the breaking up of ships for scrap recycling. Most ships have a lifespan of a few decades before there is so much wear that refitting and repair becomes uneconomical. Ship breaking allows materials from the ship, especially...

.

Design

In the earliest stages of the First World War the German Army

German Army (German Empire)

The German Army was the name given the combined land forces of the German Empire, also known as the National Army , Imperial Army or Imperial German Army. The term "Deutsches Heer" is also used for the modern German Army, the land component of the German Bundeswehr...

's rapid advance along the North Sea coast found the German Imperial Navy without submarines suitable to operate in the narrow and shallow seas off Flanders. By 18 August 1914, two weeks after the German invasion of Belgium

Belgium

Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...

, the planning of a series of small coastal submarines had already begun.

The German Imperial Navy stipulated that the submarines must be transportable by rail, which imposed a maximum diameter of 10 in 4 in (3.15 m). The rushed planning effort—which had been assigned the name "Project 34"—resulted in the Type UB I design, created specifically for operation from Flanders. The boats were to be about 92 feet (28 m) long and to displace about 125 tonnes (123 LT) with two bow torpedo tubes.A further refinement of the design—replacing the torpedo tubes with mine chutes but changing little else—led to the Type UC I

German Type UC I submarine

The Type UC I submarines were a class of small coastal minelaying U-boats built in Germany during the early part of World War I. They were the first operational minelaying submarines in the world . A total of fifteen boats were built...

 coastal minelaying submarine. Miller, p. 458.

Boats of the Type UB I design were built by two manufacturers, Germaniawerft

Friedrich Krupp Germaniawerft

Friedrich Krupp Germaniawerft was a German shipbuilding company, located in the harbour at Kiel, and one of the largest and most important builders of U-boats for the Kaiserliche Marine in World War I and the Kriegsmarine in World War II.-History:The company was founded in 1867 by Lloyd Foster, as...

 of Kiel and 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, which led to some variations in boats from the two shipyards. The eight Germaniawerft-built boats were slightly longer at 92 in 2 in (28.09 m) length overall, while the twelve Weser-built boats came in 8 inches (20.3 cm) shorter than their counterparts. All were 10 in 6 in (3.2 m) abeam

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...

 and had a draft of 9 in 10 in (3 m). The boats all displaced 127 tonnes (125 LT) while surfaced, but differed slightly in displacement submerged. The slightly longer Germaniawerft boats displaced 142 tonnes (139.8 LT) while submerged, as they weighed 1 tonne (0.984203533290685 LT) more than the Weser boats.

The drivetrain of the boats consisted of a single propeller shaft driven by a Daimler (Germaniawerft) or Körting

Körting Hannover

Körting Hannover AG is a long-standing industrial engineering company in Hanover.At the end of the 19th and beginning of the 20th century, the company played a leading role in the development of injector pumps in Germany and Europe.Körting still produces pump and pump-based vacuum technology, but...

 (Weser) 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...

 on the surface, or a Siemens-Schuckert

Siemens-Schuckert

Siemens-Schuckert was a German electrical engineering company headquartered in Berlin, Erlangen and Nuremberg that was incorporated into the Siemens AG in 1966....

 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...

 for underwater travel. The Weser boats were capable of nearly 7.5 knots on the surface and a little more than 6 knots submerged. The Germaniawerft boats were about 1 knots slower than their Bremen-made counterparts. The boats were equipped with two 45 centimetres (17.7 in) bow torpedo tubes and carried two torpedoes. They were also armed with a single 8 millimetre (0.31496062992126 in) machine gun affixed to the deck.

Construction

The German Imperial Navy ordered its first fifteen Type UB I boats on 15 October 1914. Eight boats—numbered UB-1 to UB-8—were ordered from Germaniawerft of Kiel, and seven boats—numbered UB-9 to U-15—from AG Weser of Bremen. After two of the class, UB-1 and UB-15, were sold in February 1915 to ally Austria-Hungary (becoming U-10 and U-11 in the Austro-Hungarian Navy), the German Imperial Navy ordered UB-16 and UB-17 from Weser. A further three for Austria-Hungary —U-15, U-16, and U-17—had been ordered from Weser by April, bringing the total number constructed to twenty.In the Austro-Hungarian Navy, the Type UB I boats were known as the U-10 class.

UB-1 and UB-2 were laid down on 1 November 1914 at the Germaniawerft yard at Kiel. UB-1 was launched on 22 January 1915, just 75 working days later. UB-2s launch followed on 13 February. Among the Weser boats, UB-9 was laid down first, on 6 November 1914, and launched on 6 February 1915, a week ahead of UB-2. These first three boats launched underwent trials in home waters, but most of the other members of the class were shipped via rail and underwent trials at their assembly point.

The process of shipping the submarines by rail involved breaking the submarines down into what was essentially a knock down kit. Each boat was broken into approximately fifteen pieces and loaded on to eight railway flatcar

Flatcar

A flatcar is a piece of railroad or railway rolling stock that consists of an open, flat deck on four or six wheels or a pair of trucks or bogies . The deck of the car can be wood or steel, and the sides of the deck can include pockets for stakes or tie-down points to secure loads...

s. Type UB I boats destined for service with the Flanders Flotilla made a five-day journey to Antwerp for the two- to three-week assembly process. After assembly at Antwerp the boats were towed by barge to Bruges

Bruges

Bruges is the capital and largest city of the province of West Flanders in the Flemish Region of Belgium. It is located in the northwest of the country....

 for trials. Boats selected for service in the Mediterranean were sent to the Austro-Hungarian port of Pola for assembly. The total time from departure of the railcars from the shipyard to operational readiness for the boats was about six weeks.

By July 1915 all seventeen of the German Imperial Navy Type UB Is had been completed.

Service

During their trials the Type UB Is were found to be too small and too slow and had a reputation for being underpowered; one commander compared his Type UB I to a "sewing machine

Sewing machine

A sewing machine is a textile machine used to stitch fabric, cards and other material together with thread. Sewing machines were invented during the first Industrial Revolution to decrease the amount of manual sewing work performed in clothing companies...

". According to authors R. H. Gibson and Maurice Prendergast in their 1931 book The German Submarine War, 1914–1918, the UBs did not have enough power to chase down steamers while surfaced and lacked the endurance to spend any extended amount of time underwater, exhausting their batteries after little over an hour's running. In-service use revealed another problem: with a single propeller shaft/engine combination, if either component failed, the U-boat was almost totally disabled.Many of the problems with the Type UB I design were rectified in the larger 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...

 which had twin propellers, larger engines, and a higher top speed. Williamson, p. 13.

Another reported problem with the Type UB Is was the tendency to break trim after the firing of torpedoes. The boats were equipped with compensating tanks designed to flood and offset the loss of the C/06 torpedo's 1700 pounds (771.1 kg) weight, but this system did not always function properly; as a result, 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 in June 1915, the tank failed to properly compensate, forcing the entire crew to run to the stern to offset the trim imbalance.

Despite the problems, the "tin tadpoles", as the Germans referred to them, were in active service from March 1915 through the end of the war, with half of the twenty boats lost during the war. Boats of the class served in three navies: the German Imperial Navy, the Austro-Hungarian Navy, and the Bulgarian Navy. In German service, they served primarily in the Flanders Flotilla, the Baltic Flotilla, and the Constantinople Flotilla.

Flanders Flotilla

The first Type UB I to enter service was UB-10, which formed the nucleus of the Flanders Flotilla, on 27 March 1915. By the end of April five more Type UB I boats had become operational. UB-10 was eventually joined in the Flanders Flotilla by UB-2, UB-4, UB-5, UB-6, UB-12, UB-13, UB-16, and UB-17; of these, only UB-2 made the journey to Flanders by sea rather than rail.

UB-4 departed on the first patrol from Flanders on 9 April, and was responsible for sinking the first ship sent down by the flotilla. The Type UB I boats of the Flanders Flotilla originally patrolled the area between the United Kingdom and the Netherlands, but began patrolling the English Channel

English Channel

The English Channel , often referred to simply as the Channel, is an arm of the Atlantic Ocean that separates southern England from northern France, and joins the North Sea to the Atlantic. It is about long and varies in width from at its widest to in the Strait of Dover...

 after UB-6 pioneered a route past British antisubmarine nets and mines in the Straits of Dover in late June.

Over the Type UB Is' first year of service, UB-4 and UB-13 were both lost, and UB-2 and UB-5 were transferred to the Baltic Flotilla. In March 1917, UB-6 ran aground in Dutch waters and was interned for the rest of the war, along with her crew.UB-6 entered Dutch territorial waters due to a navigational error, and ran aground. Because the Netherlands was neutral during the war, and UB-6 did not leave Dutch territorial waters within 24 hours as required by international law, the submarine and her crew were interned by the Dutch. Germany protested, but because UB-6's grounding was the result of an error and not because of distress, the Dutch could not release the submarine. The four remaining Type UB Is in Flanders—UB-10, UB-12, UB-16, UB-17—were all converted to minelayers by 1918, having their torpedo tubes removed and replaced with chutes to carry up to eight mines. All but UB-10 were lost in 1918; UB-10, in poor repair and out of service, was scuttle

Scuttling

Scuttling is the act of deliberately sinking a ship by allowing water to flow into the hull.This can be achieved in several ways—valves or hatches can be opened to the sea, or holes may be ripped into the hull with brute force or with explosives...

d in October 1918 when the Germans evacuated from Flanders.

Baltic Flotilla

UB-9 was initially assigned to the Baltic Flotilla, and was joined by UB-2 and UB-5 in early 1916. All three became training boats at Kiel in 1916, joining UB-11 in that duty. Little information is available about the Type UB I boats operating in the Baltic

Baltic Sea

The Baltic Sea is a brackish mediterranean sea located in Northern Europe, from 53°N to 66°N latitude and from 20°E to 26°E longitude. It is bounded by the Scandinavian Peninsula, the mainland of Europe, and the Danish islands. It drains into the Kattegat by way of the Øresund, the Great Belt and...

.

Constantinople Flotilla

Four of the German Imperial Navy boats—UB-3, UB-7, UB-8, and UB-14—were selected for service with the Constantinople Flotilla. All were sent to Pola for assembly and trials there as part of the Pola Flotilla

Pola Flotilla

The Pola flotilla was an Imperial German Navy formation set up to prosecute the U-boat campaign against Allied shipping in the Mediterranean during the First World War in support of Germany’s ally, the Austro-Hungarian Empire...

before sailing on to join the Constantinople Flotilla. UB-3 disappeared en route to Constantinople in May 1915, but the other three arrived there by mid-June.

The three Type UB I boats of the Constantinople Flotilla seem to have patrolled primarily in the Black Sea

Black Sea

The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...

. UB-8 was transferred to the Bulgarian Navy in May 1916, and UB-7 disappeared in the Black Sea in October 1916, leaving UB-14 as the sole remaining German Type UB I in the flotilla; she was surrendered at Sevastopol

Sevastopol

Sevastopol is a city on rights of administrative division of Ukraine, located on the Black Sea coast of the Crimea peninsula. It has a population of 342,451 . Sevastopol is the second largest port in Ukraine, after the Port of Odessa....

 in November 1918 to French armies stationed there during the Russian Civil War

Russian Civil War

The Russian Civil War was a multi-party war that occurred within the former Russian Empire after the Russian provisional government collapsed to the Soviets, under the domination of the Bolshevik party. Soviet forces first assumed power in Petrograd The Russian Civil War (1917–1923) was a...

.

Austro-Hungarian Navy

UB-1 and the still incomplete UB-15 were sold to the Austria-Hungary in February 1915; both were dismantled and shipped to Pola in May. After one cruise under the German flag, each boat was commissioned into the Austro-Hungarian Navy. The pair—renamed U-10 and U-11, respectively—were joined by U-15, U-16, and U-17 in October. Known as the U-10 or the Okarina (Ocarina

Ocarina

The ocarina is an ancient flute-like wind instrument. Variations do exist, but a typical ocarina is an enclosed space with four to twelve finger holes and a mouthpiece that projects from the body...

) class as a part of the Austro-Hungarian Navy, the five boats operated primarily in the Adriatic in patrols off Italy 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...

. U-10 (ex UB-1) hit a mine in July 1918 and was beached, but had not been repaired by the end of the war. U-16 was sunk after she torpedoed an Italian destroyer in October 1916, and the remaining three (and the unrepaired U-10) were ceded to Italy at the end of the war.

Bulgarian Navy

After UB-8 was transferred to the Bulgarian Navy in May 1916, she was renamed Podvodnik No. 18 (in Cyrillic

Cyrillic alphabet

The Cyrillic script or azbuka is an alphabetic writing system developed in the First Bulgarian Empire during the 10th century AD at the Preslav Literary School...

: Пoдвoдник No. 18). She was Bulgaria's first submarine, and was engaged primarily in coastal defense duties off Bulgaria's main Black Sea port of Varna

Varna

Varna is the largest city and seaside resort on the Bulgarian Black Sea Coast and third-largest in Bulgaria after Sofia and Plovdiv, with a population of 334,870 inhabitants according to Census 2011...

. Podvodnik No. 18 survived the war and was ceded to France after the Treaty of Neuilly-sur-Seine.

List of Type UB I submarines

Twenty Type UB I submarines were built, 17 for the German Imperial Navy and three for the Austro-Hungarian Navy. Two of the German submarines—UB-1 and UB-15—were sold to Austria-Hungary and commissioned into the Austro-Hungarian Navy as U-10 and U-11, respectively. Those two and a further three built by AG Weser comprised the virtually identical U-10 class for the Austro-Hungarian Navy. Another of the German submarines, UB-8, was sold to Bulgaria in May 1916, becoming Podvodnik No. 18.

German Imperial Navy

• SM UB-1 (became the Austro-Hungarian U-10, July 1915) (became the Bulgarian Podvodnik No. 18, May 1916) (became the Austro-Hungarian U-11, June 1915)

Austro-Hungarian Navy

In the Austro-Hungarian Navy the Type UB I boats were known as the U-10 class, which consisted of two former German Type UB I boats and three built specifically for Austria-Hungary.

• SM U-10 (the former German UB-1)
• SM U-11 (the former German UB-15)

In addition, four of the German Type UB Is assigned to the Pola Flotilla based at the Austro-Hungarian Navy's main naval base at Pola were assigned Austro-Hungarian designations.After Italy had entered the First World War by declaring war on Austria-Hungary on 23 May 1915, Germany felt treaty-bound to support the Austro-Hungarians in attacks against Italian ships, even though Germany and Italy were not officially at war. As a result, German U-boats operating in Mediterranean were assigned Austro-Hungarian numbers and flags. After 28 August 1916, when Germany and Italy were officially at war, the practice continued, primarily to avoid charges of flag misuse. The practice was largely ended by 1 October 1916 except for a few large U-boats that continued using Austro-Hungarian numbers. Gardiner, p. 341.
(as U-9) (as U-7) (as U-8) (as U-26)Sometimes cited as U-26 in the Austro-Hungarian Navy but she was never officially transferred to the Austro-Hungarian Navy from the German Imperial Navy. Sokol, p. 109.

These four boats remained under commission in the German Imperial Navy, retained German crews and commanders, and received orders from the German flotilla commander at Pola.

Bulgarian Navy

Germany and Bulgaria negotiated the purchase of two UB I boats for the Bulgarian Navy, and , in 1916. Two crews of Bulgarian sailors were sent to Kiel for training. Before the purchase could be completed, UB-7 was sunk, leaving only one boat for Bulgaria. On 25 May 1916, UB-8 was officially transferred to Bulgaria for the remainder of the war.

• Podvodnik No. 18 (the former German UB-8)

Type UB I submarines

Name of U-boat	Date launched	Date commissioned	Ships sunk, damaged, or taken as a prize	Fate
UB-1/U-10			1	Handed over to Italy as a war reparation and scrapped at Pola by 1920.
UB-2			11	Broken up by Stinnes on 3 February 1920.
UB-3			0	Disappeared after 23 May 1915.
UB-4			4	Sunk by British Q ship on 15 August 1915.
UB-5			5	Broken up by Dräger Dräger The Drägerwerk AG is a German company based in Lübeck which makes breathing and protection equipment, gas detection and analysis systems, and noninvasive patient monitoring technologies. Customers include hospitals, fire departments and diving companies....  at Lübeck Lübeck The Hanseatic City of Lübeck is the second-largest city in Schleswig-Holstein, in northern Germany, and one of the major ports of Germany. It was for several centuries the "capital" of the Hanseatic League and, because of its Brick Gothic architectural heritage, is listed by UNESCO as a World...  in 1919.
UB-6			9	Scuttled by her crew at Hellevoetsluis Hellevoetsluis Hellevoetsluis is a small city and municipality on Voorne-Putten Island in the western Netherlands, in the province of South Holland...  on 18 March 1917. Her wreck was later raised and broken up at Brest Brest, France Brest is a city in the Finistère department in Brittany in northwestern France. Located in a sheltered position not far from the western tip of the Breton peninsula, and the western extremity of metropolitan France, Brest is an important harbour and the second French military port after Toulon...  in July 1921.
UB-7			1	Disappeared after 27 September 1916.
UB-8/Podvodnik No. 18			2	Handed over to the French on 23 February 1919. Later towed to Bizerta, where she was scrapped after August 1921.
UB-9			0	Broken up by Dräger at Lübeck in 1919.
UB-10			37	Scuttled off Flanders on 5 October 1918.
UB-11			0	Broken up by Stinnes on 3 February 1920.
UB-12			24	Disappeared after 19 August 1918.
UB-13			12	Sunk on 24 April 1916.
UB-14			7	Surrendered at Malta in November 1918 and broken up in 1920.
UB-15/U-11			1	Handed over to Italy as a war reparation and scrapped at Pola in 1920.
UB-16			26	Torpedoed by HMS E34 HMS E34 HMS E34 was a British E class submarine built by John Thornycroft, Woolston, Hampshire. She was laid down on 21 January 1917 and was commissioned in March 1917.-Service history:HMS E34 sank the U-Boat off Harwich in the North Sea on 10 May 1918.... on 10 May 1918.
UB-17			16	Disappeared after 11 March 1918.
U-15			6	Handed over to Italy as a war reparation and scrapped at Pola in 1920.
U-16			3	Sunk on 17 October 1916.
U-17			1	Handed over to Italy as a war reparation and scrapped at Pola in 1920.

Key

	U-boat belonging to Bulgaria.
	U-boat belonging to Germany.
	U-boat belonging to Austria-Hungary.