The Central Powers submarines in the Mediterranean during WWI

by Robert Derencin


The Central Powers was name of military alliance of Germany and Austro-Hungarian Monarchy in WWI. Turkey and Bulgaria then joined the alliance during WWI. On the other side, there was military alliance of Great Britain, France and Russia- "Entente" or "Triple Entente". During the war some countries joined the Entente, for example the USA, Italy and Japan. The Central Powers planned (before the war) that Italy would be part of their alliance. But, in 1915 Italy joined the Entente.

For easier understanding of this article members of the Entente will be called "the Allies" and their ships and units will be called "Allied".

On the Central Powers’ side in the Mediterranean there were the Austro-Hungarian Navy, German Mediterranean division and (small) Turkish Navy. In 1914, immediately after the beginning of the war, German Mediterranean division (battle cruiser Goeben and light cruiser Breslau, under command of Rear Admiral Souchon) succeeded in arriving at Istanbul. Then, the Mediterranean division formally joined the Turkish Navy, with the both warships and the warships’ crews. Rear Admiral Souchon became commanding officer of the Turkish Navy.

On the Allied side, in the Mediterranean, there were the French Navy, the British Royal Navy and the Italian Navy. From 1917 the naval warfare in the Mediterranean also involved the US Navy and the Imperial Japanese Navy.

Naval warfare in the Mediterranean Sea was vital for the war efforts of all nations involved. There were several war theatres around the Mediterranean basin; Balkan, Asian-Turkish (Palestine, of that time) and Italian battlefields. But, naval operations in the Mediterranean Sea also affected situation on others war theatres such as West European (France and Belgium), East European (Russian front) and Asian-Turkish (Caucasus). Intention of this article is to explain activities of the Central Powers (Austro-Hungarian and German) submarines in the Mediterranean Sea and their effect on WWI.

Austro-Hungarian Navy

The Austro-Hungarian Navy is not as well known as navies of other big countries involved in WWI. The Austro-Hungarian Navy (k.u.k. Kriegsmarine) was well organised and a very interesting navy. In the Navy there was a submarine flotilla and its submarines succeeded in keeping enemy (i.e. the Allied) warships out of Austro-Hungarian waters, as much as possible. For easier understanding, Austro-Hungarian coast was on East Side of the Adriatic Sea, from Trieste to Kotor (Cattaro). Austro-Hungarian main naval base was in Pula (Pola), a town placed on the south part of Istrian peninsula. As the time passed, the Austro-Hungarian Navy organised itself, built a strong and modern fleet and created all kinds of naval infrastructure like ports, fortifications, the naval shipyard, chain of lighthouses along the Eastern Adriatic coast and so on. Also, the Austro-Hungarian Navy charted the whole Adriatic. The Austro-Hungarian ships (cruisers) even went on very distant voyages to China and Japan, for example. The Navy also had a lot of naval hydroplanes. Together the official improvements, there were some unofficially improvements, very important to naval history, like the invention of the torpedo.

"The Coast Rescuer"
During the 19th century Fregattenkapitan Ivan Lupis (a Croat which served in the Austro-Hungarian Navy at Pula) invented a "strange" weapon called "coast rescuer". Original intention for the weapon was for it to be launched from a coast towards enemy ships, thus the name.

In 1866, Fregattenkapitan Ivan Lupis along with British engineer Robert Whitehead improved the idea and protected it by a patent. Robert Whitehead established the world’s first torpedo factory in Rijeka, Croatia and started production. In the beginning the name of the new weapon was "Minenschiff", but soon the name was changed to its current name "torpedo", after the fish named "electric ray", or Torpedo marmorata in the Latin language.

It is impossible to describe the Austro-Hungarian Navy in just one article. The Navy existed for only a few decades but during those years the Navy made incredible progress. The Navy consisted of a strong fleet, modern naval aviation, excellent naval schools, shipyard etc. Fortifications around main naval base Pula were strong and, for the period, modern. The fortifications still exist and are a testament of the presence of a strong navy one hundred years ago.

Ranks in the Austro-Hungarian Navy

The Navy ranks were divided into few groups; sailors, junior non-commissioned officers (NCO’s), senior NCO’s, naval officers. In this chapter just some branches, interesting to submarines will be covered: helm (Steuer), torpedo, telegraphy (Telegraphen), engine (Maschinen), electricity (Elektro).

Military service (conscription) in the Austro-Hungarian Navy lasted for four years. The first year sailors (Matrosen) were Matrose 4. Klasse (4th Class Sailor). Second year sailors have been promoted in the rank of Matrose 3. Klasse (3rd Class Sailor). In the third and fourth years of military service sailors have been promoted in the rank of Matrose 2. Klasse (2nd Class Sailor). Sailors have been promoted in the rank of Matrose 1. Klasse (1st Class Sailor) just exceptionally. After four years in active service, the sailors spent five years in naval reserve and then three years in coastal defence; "Seewehr".

Table 1 shows the sailors’ ranks. In most branches just rank of Matrose 1. Klasse had its speciality.

Table 1: Sailors

Deck-dienst Steuer, Torpedo, Telegraphen, Maschinen, Elektro-dienst
4. Klasse
3. Klasse
Matrose 3. Klasse Torpedomann
2. Klasse
Matrose 2. Klasse Torpedomann
Matrose 2. Klasse Torpedovormann
1. Klasse
Steuermatrose, Matrose 1 Klasse Torpedomann / Matrose 1. Klasse Torpedovormann, Telegraphenmatrose, Maschinenmatrose, Elektromatrose

Junior NCO’s
The junior NCO’s were professionals. There were two ways how to become the junior NCO. Some sailors, after their military service (conscription), signed contract with the Navy and stayed in the Navy four years more. In the beginning they have been promoted in the rank of Matrose 1 Klasse (1st Class Sailor) and lately they have been promoted in the junior NCO’s ranks. But, in the most usual way, future NCO’s graduated in one of the naval schools and became the junior NCO’s. The junior NCO’s were dressed in ordinary sailor’s uniform, with NCO’s emblems.

Table 2: Junior NCO's ranks

Deck- dienst Steuer, Torpedo, Telegraphen, Maschinen, Elektro- dienst
Marsgast Steuergast, Marsgast Torpedoinstruktor, Marsgast Telegraphist, Maschinengast, Elektrogast
Quartier- meister Steuerquartiermeister, Quartiermeister Torpedoinstruktor, Quartiermeister Telegraphist, Maschinenquartiermeister, Elektroquartiermeister
Bootsmanns- maat Steuermannsmaat, Bootsmannsmaat Torpedoinstruktor / Bootsmannsmaat Torpedomeister, Bootsmannsmaat Telegraphist / Bootsmannsmaat Telegraphenmeister, Maschinenmaat, Elektromaat

Senior NCO’s
After years of service the junior NCO’s could be promoted in the rank of senior NCO’s, if there were empty positions for the senior NCO rank. The senior NCO’s were dressed in uniform similar to officers. Also, the senior NCO’s had right to a monthly salary, insured service and a pension after their active service.

Table 3: Senior NCO’s ranks

Deck- dienst Steuer, Torpedo, Telegraphen, Maschinen, Elektro-dienst
Bootsmann Steuermann, Bootsmann Torpedomeister, Bootsmann Telegraphenmeister, Maschinenwarter, Elektrowarter
Stabsbootsmann Stabssteuermann,
Stabsbootsmann Torpedomeister,
Stabstelegraphenmeister, Stabsmaschinenwarter, Stabselektrowarter
Oberstabs- bootsmann Oberstabssteuermann,
Oberstabsbootsmann Torpedomeister, Oberstabstelegraphenmeister, Oberstabsmaschinenwarter, Oberstabselektrowarter

The officers ranks were also divided into few groups of ranks: officer candidates, officers, staff officers and flag officers ranks. Also, their branches divided officers i.e. deck (navigational) officers, engineers, medical officers, officials, naval chaplains etc. Table 4 shows deck officers’ ranks.

Table 4: Ranks of deck officers of the Austro-Hungarian Navy

Officer candidates Seeaspirant
(Junior Officers)
Staff officers
(Senior Officers)
Flag officers

The Naval Academy and naval schools

The educational system in the Austro-Hungarian Navy was excellently organised and, for the period, very modern. There were many courses and schools. In this chapter will be elaborated just three schools, the two schools for non-commissioned officers and the Naval academy for future officers.

K.u.k. Schiffsjungenschule
The k.u.k. Schiffsjungenschule (Maritime school) was in Sibenik (Sibenico). The school program lasted for three years. Program of the school was basic military and basic naval knowledge, without any particular naval speciality. The school students were drilled on the school’s boats and ships and on the school’s training fields. The graduated students became junior NCO’s. The excellent students were promoted to the rank of Quartiermeister. The second-best students got the rank of Marsgast. The good students have been promoted in the rank of Matrose 1. Klasse. The sufficient students were promoted to the rank of Matrose 2. Klasse. After that, all ex students (now the new junior NCO’s) went to some speciality courses, to study their own speciality.

K.u.k. Maschinenschule
The k.u.k. Maschinenschule (Military school of Mechanical Engineering) was in Pula (Pola). The school program lasted for three years. The school prepared future NCO’s for two specialities; the engine speciality (Maschinendienst) and the electric-speciality (Elektrodienst). The school was excellent, and as a matter of fact the school was one of the first electrical-engineering schools in Europe. After graduation the students were promoted in the same way as the students of Maritime school in Sibenik (mentioned above). But, unlike them, the students of k.u.k. Maschinenschule had their own speciality courses immediately after graduation.

K.u.k. Marine-Academie
K.u.k. Marine-Akademie (Naval academy) was in Rijeka (Fiume). Future naval officers came to the Naval academy at the age of 15 or 16 years old. After graduation they got promoted to the rank of Seekadett. After a time of service in the rank of Seekadett, they were promoted to Seefahnrich (senior officer candidate). Most of naval officers (i.e. line officers) came from the Naval academy.

Sometimes the Navy needed more naval officers and in that case the Navy announced vacancies for future naval officers. Graduated gymnasium (high school) students went to an eighteen-month course. The course consisted of ten-month theoretical part and eight-month practical part (onboard). During the course students were promoted to the rank of Seeaspirant. After the course and final examinations, students became Seekadett. Limited duty officers (e.g. engineers, medical doctors and chaplains, etc) came from civilian colleges.

Austro-Hungarian submarines

The first Austro-Hungarian submarines were U1 and U2, "Lake" type, built in Pula. Another two submarines were U3 and U4, German type "Germania", built in Kiel (Germany) and towed up to Pula. Submarines U1 and U2 (in service since 1911) were only used for training service, later in the war U1 and U2 were used as floating torpedo batteries in Trieste. Submarines U3 and U4 (in service since 1909) were used for actions in the Adriatic Sea during the war.

Technical characteristics of "Lake" and "Germania" type of submarines:

Type "Lake", U1 and U2 Type Germania, U3 and U4
Displacement (surfaced/submerged) in tons 230 / 270 after reconstruction 223 / 277.5 240 / 300
Dimensions (length/width/raft) In metres 30.5 / 4.8 / 3.9 42.3 / 4.5 / 3.8
Engines 2 gasoline powered (after reconstruction 2 diesel) and 2 electric engines 2 gasoline powered and 2 electric engines
Power of propulsion (engines) in horse powers 560 and 200 after reconstruction 720 and 200 600 and 320
Speed (surfaced/submerged) 10 / 6 12 / 8
Operational range (surfaced/submerged) 950/40 1200 at speed of 12 knots / 40 at speed of 3 knots
Armaments 3 torpedo tubes 450 mm (2 bow 1 aft) 1 deck gun 37 mm L/23 2 bow torpedo tubes 450 mm (3 in reserve)
Crew 3 officers 14 NCO 21

Then, U5 and U6, type "Holland", built in factory of torpedoes in Rijeka (Fiume). After the beginning of WWI and mobilisation, U12 (improved "Holland" type), built in the torpedo factory at Rijeka, was included in the Austro-Hungarian Navy. In the beginning of WWI the Navy had just 7 submarines plus 4 submarines under construction.

On 20 December 1914 at noon the French Navy submarine "Curie" attempted to penetrate the harbour of Pula. The submarine, submerged at depth of 20 metres, was caught in anti-submarine net and sank. The submarine was raised on 31 January 1915 and attached in the Austro-Hungarian Navy active service, as U14, on 1 June 1915.

Technical characteristics of "Holland" type of submarines and submarine U14 (ex-French "Curie"):

"Holland" type, U5, U6 and U12 U14 (after modification in 1916/1917)
Displacement (surfaced/submerged) in tons 240 / 273 397 / 551
Dimensions (length/width/raft) In metres 32.09 / 4.23 / 3.9 52.2 / 5.2 / 3.2
Engines 2 gasoline and 2 electric powered engines 2 diesel "Korting" and 2 electric engine
Power of propulsion (engines) in horse powers 500 and 230 840 and 660
Speed (surfaced/submerged) in knots 10.75 / 8.5 12.6 / 9
Operational range (surfaced/submerged) 800 at speed of 8.5 knots/ 48 at speed of 6 knots 6500 / 84
Armaments 2 torpedo tubes 450 mm 1 deck gun 37 mm (lately 47 mm, 75 mm on U5) 2 torpedo tubes 533 mm 2 deck guns (88 mm and 47 mm)
Crew 4 officers 15 NCO and sailors (U12- 2 officers and 15 NCO and sailors) 28

Submarines U15, U16 and U17 (type "UB I") were built in Germany, transported in pieces to Pula by train and pieced together in shipyard in Pula. The German Navy submarines UB1 and UB15 were bought, transported to Pula by train, pieced together as other submarines of that type and included in the Austro-Hungarian Navy as U10 (ex-German UB1) and U11 (ex-German UB15). The submarines U10, U11, U15, U16 and U17 were in service since 1915. U10 were firstly built in Kiel, other submarines were built in Bremen.

The "UB I" type submarines were able for actions in shallow sea and lagoons of the Northern Adriatic Sea, but not able for longer cruising in the Southern Adriatic and South of the Otranto barrage. U11 (ex-German UB15), with German crew, sank on 10th June 1915 Italian submarine "Medusa" in the vicinity of Venezia.

Technical characteristics of "UB I" type of submarines:

Type "UB I", U11, U15, U16, U17 Type "UB I", U10
Displacement (surfaced/submerged) in tons 127.5 / 142.5 125.5 / 140.25
Dimensions (length/width/raft) In metres 27.88 / 3.15 / 2.73-3.03 27.88 / 3.15 / 2.73-3.03
Engines 1 diesel "Korting" and 1 electric engine 1 diesel "Daimler" and 1 electric engine
Power of propulsion (engines) in horse powers 60 and 120 60 and 120
Speed (surfaced/submerged) in knots 6.5 / 5.5-9 6.5 / 5.5-9
Operational range (surfaced/submerged) 1200 / 65 1200 / 65
Armaments 2 torpedo tubes 450 mm (1 in reserve) 1 deck gun 47 mm L/23 (U17- 37 mm L/33, U11- lately 66 mm L/18) 2 torpedo tubes 450 mm (1 in reserve) 1 deck gun 37 mm L/23
Crew 2 officers 13 NCO and sailors (for longer cruising one officer more) 2 officers and 13 NCO and sailors (for longer cruising one officer more)

Another Austro-Hungarian submarines were "Havmanden" class. Submarines U20 and U23 were built in Pula and submarines U21 and U22 were built in Rijeka. The submarines were in service since 1917. In the beginning of the service, the submarines were already old-fashioned.

The most modern and capable (in active service) Austro-Hungarian submarines were type "UB II" U27 class submarines. Submarines U27, U28, U40 and U41 were built in Pula. U29, U30, U31 and U32 were built in Rijeka. The submarines were in service since 1917 (U41 since 1918). The submarines were used for all kind of actions. U31 was in action in the Mediterranean Sea, East of Malta. After that, U31 was once more time in action in the Mediterranean Sea. U32 was several times in the Mediterranean Sea, in the Ionian Sea, in the Bay of Taranto and East of Malta.

Technical characteristics of "Havmanden" and "UB II" (class U27) Type of submarines:

Type "Havmanden", U20, U21, U22, U23 Type "UB II" (class U27), U27-32, U40, U41
Displacement (surfaced/submerged) in tons 173 / 210 268 / 306
Dimensions (length/width/raft) In metres 38.8 / 4 / 2.8 36.9 (U41- 37.6) / 4.75 / 3.72
Engines 1 diesel and 1 electric engine 2 diesel engines and 2 electric engines on two axles
Power of propulsion (engines) in horse powers 450 and 160 300 and 280
Speed (surfaced/submerged) in knots 12 / 9 9 / 7.5 (U41- 9.3 / 7)
Operational range (surfaced/submerged) 2000 / 54-71 4000 / 45-130
Armaments 2 torpedo tubes 450 mm 1 deck gun 66 mm L/26 1 machine-gun 2 bow torpedo tubes 450 mm (5 torpedoes onboard) 1 deck gun 75 mm L/30 1 machine gun
Crew 18 19

German submarines UB 43 and UB 47 (type "UB II") were transported from Germany to Pula by train in pieces and then pieced together in shipyard in Pula. The submarines firstly operated as German submarines, UB43 from 24th April 1916 and UB47 from 4th July 1916. The Austro-Hungarian Navy took over the submarines (which were in very bad condition) and from 30th July 1917 the submarines operated as Austro-Hungarian U43 (ex-German UB43) and U47 (ex-German UB47).

In WWI the Austro-Hungarian Navy had 27 operational submarines. During the war the Navy planned to build bigger and stronger (ocean-going) submarines, some of the submarines were in construction in shipyards in Rijeka and Pula but never completed. In spite of it, the Austro-Hungarian submarines fought very successfully and succeeded to keep the eastern Adriatic coast (more or less) "clear" of the allied naval forces. Also, the submarines endangered Italian maritime traffic all around the Adriatic Sea.

Austro-Hungarian submarines sank a total of 117 ships (220,121 BRT) during WWI. The submarines were based in two ports, Pula (the Austro-Hungarian submarine’s flotilla command place) and Kotor. In Pula, the flotilla used ship "Pelican" as its base and command place. Old ship "Gaa" was used for the same purpose in Kotor.

Here are some more important successes of the Austro-Hungarian submarines:

The Otranto barrage
The most successful combined action of the Austro-Hungarian Navy was during the Austro-Hungarian Fleet attack against the Otranto barrage, on 15th May 1917. The Allies organised the Otranto barrage in attempt to stop penetration of the German Navy and the Austro-Hungarian Navy submarines from the Adriatic Sea into the Mediterranean Sea. The Austro-Hungarian Navy ships from Kotor (3 cruisers and 2 destroyers) attacked the Otranto barrage and fought with the Allies’ ships, which were there. German submarine UC 25 set down mines in front of Brindisi. After that, the UC 25 patrolled the Brindisi front. Austro-Hungarian submarine U4 watched in the front of Albanian port Valona. Also, Austro-Hungarian submarine U27 cruised between Brindisi and Kotor.

The Allies sent 3 cruisers and 4 destroyers from Brindisi to protect the Otranto barrage. During the Allies’ warships return from the Otranto barrage to Italian port Brindisi, after the fight with the Austro-Hungarian Fleet’s ships, U27 torpedoed and damaged British cruiser "Dartmouth" (the ship finally succeeded to reach Brindisi). One allied ship, French destroyer "Boutefeu", who tried to help the cruiser, sank because of mine (from the German UC 25).

It is important to mention that in this action were involved Austro-Hungarian surface forces, naval aeroplanes and submarines. Co-operation between the Austro-Hungarian units and German submarine UC-25 was excellent. During the action radio stations installed on the Austro-Hungarian cruisers successfully hampered the allied radio traffic.

Austro-Hungarian Navy recalls the boats
On 17th November 1918 the Austro-Hungarian Navy Command ordered to all its submarines, which were on sea, return to their bases. Before that, the last Austro-Hungarian submarines returned to base from cruising were U29 and U14, on 1st November 1918.

After the end of WWI and after collapse of Austro-Hungarian Empire, Austro-Hungarian submarines in Pula and in Kotor fell in Italian and French hands. Submarines, which were in construction, in Pula and in Rijeka, were destroyed in shipyards. The all captured Austro-Hungarian submarines were scuttled sooner or later. Submarine U14 (ex-Curie) was returned to the French Navy, renamed "Curie" and continued her service.

Austro-Hungarian submarines lost in action during WWI

The German Navy Mediterranean submarine flotilla

German submarines started with operations in the Adriatic Sea and in the Mediterranean Sea in the summer of 1915. In the first time the submarines (with German crews) operated under Austro-Hungarian flag and the each submarine temporarily had Austro-Hungarian submarines’ sign (i.e. serial numbers). Once when Germany declared war to Italy, on 28th August 1916, the submarines mainly returned under German flag. Their original serial numbers were returned as well. Because of some reasons, some of the submarines continued with operations under Austro-Hungarian flag and serial numbers.

The first German submarines (types "UB I" and "UC I") arrived in Pula from Germany by train, in pieces. Submarines UC 12, UC13, UC 14, UC 15 and UB14 were pieced together in the shipyard in Pula and started operations in June 1915.

Type "UB II" submarines (UB 42, UB 44, UB 45 and UB 46) also arrived in Pula by train. After the arrival, the submarines were pieced together in naval shipyard in Pula and started operating between March and June 1916.

"Mittel-U" class submarines arrived from Germany in the Adriatic by sea. Submarine U 21 (type U19) came in Kotor on 13th May 1915, for supplying and then proceeded to Turkey. Other "Mittel-U" class submarines arrived in the Adriatic later. Submarines U 34 and U 35 (type U31) arrived in August 1915. In September 1915 arrived submarines U 33 and U 39 (type U31). Submarine U 38 (type U31) arrived in November 1915. In the period between November and December 1916 arrived in the Adriatic submarines as follows: U 47 (type U43), U 32 (type U31) and U 63, U 64, U 65 (all three submarines were type U63).

"UC II" and "UB III" types of submarines were stronger and able to come from Germany to the Adriatic by sea. Table bellow shows times and numbers of the submarines’ arrivals in the Adriatic.

Time of arrival Type "UC II" Type "UB III"
October-December 1916 UC 20, UC 23, UC 22, UC 35
January 1917 UC 34, UC 37
February 1917 UC 24
March 1917 UC 67
April 1917 UC 25, UC 27
June 1917 UC 73, UC 53
July 1917 UC 52, UC 54
September 1917 UB 48, UB 50, UB 51
October 1917 UB 49, UB 52
November 1917 UB 53
December 1917 UC 38 UB 66
January 1918 UB 68, UB 69 (sank upon arrival)
March 1918 UC 74
April-May 1918 UB 70 and UB 71 (both sank during the arrival), UB 105 (successfully arrived)
September 1918 UB128
October 1918 UB 129

In WWI two German ocean minelayer class submarines (type "UE I") operated from the Adriatic Sea as well, the U 72 (from September 1916) and U 73 (from April 1916). It is obvious that Germans sent the submarines into the Adriatic and the Mediterranean as a result of change of situation on the scene. Once when the importance of the submarine warfare in the Mediterranean became clear, the number of submarines increased. By the time, Germans realised that for such operational area as the Mediterranean is; the best submarines are stronger coastal attack and minelayers classes. Also, Germans sent same type of submarines at roughly the same time. At the same time, German engineers and workers from Kiel, specialised for same types of the submarines, arrived in the naval shipyard in Pula. Because of the experts and because of same spare parts, maintaining the the submarines was easier.

The German Mediterranean submarine flotilla officially was formed on 18th November 1915. The flotilla main base was in Pula, where the flotilla used old Austro-Hungarian cruiser "Maria Theresia" as its base ship and command place. The German submarines in the Mediterranean Sea operated mainly along the Northern African coast, from Gibraltar to Malta, on the exit of the Suez Canal and in the Aegean Sea. The submarines, which were involved in the Dardanelles’ operation, were mainly based in Kotor (Cattaro) and smaller number of them were based in Istanbul. In the Dardanelles’ operation German submarines operated at the same time in the Aegean and the Black Sea.

The German submarines were used depending of the submarines’ types and capabilities. The first arrived German submarines, UC 15 and UC 13 (type "UC I") and UB14 (type "UB I") after short period in the Adriatic were sent to Istanbul and lately operated in the Black Sea. UC 14 served as transport and minelayer submarine. UC12 served as transport submarine, from the Adriatic to Northern Africa (which was excellent for "UC I" type), and also as minelayer submarine- in the front of Durres (Albania) and Taranto (Italy). After that, all submarines of "UB II" types (UB 42, UB 44, UB 45 and UB 46) firstly operated in the Adriatic, but very soon were sent to Istanbul. UB 44 was sunk in the Strait of Otranto, other submarines succeeded to reach Istanbul.

Submarines of "UC II" type served in all areas. Submarines UC20 and UC73 served primarily as transport submarines (from the Adriatic to North Africa). UC 23 and UC 37 were sent to Istanbul (Istanbul and the Black Sea operational areas). UC 22, UC 38, UC 34 and UC 35 served in the Adriatic and in the Mediterranean, primarily as minelayer submarines.

Submarines of "UB III" type served as attack coastal torpedo submarines in the Mediterranean, except submarine UB128 that came in the area as transport submarine.

"Mittel-U" class submarines served in the Mediterranean (the first submarine, U 21 was sent to Istanbul and participated in the Dardanelles’ operation). "Mittel-U class" submarines were able for longer cruising operations, for example- along North African coast (from Gibraltar to the Suez Canal) and on ships’ route from the Suez Canal to Dardanelles.

During WWI German submarines in the Mediterranean successfully attacked and sank many allied warships and merchant ships. German’s losses of submarines in the Mediterranean increased during the war. The biggest part of the lost German submarines was type "UB", than type "UC". The submarines operated often in coastal areas, which was (and still is) very dangerous. The smallest part of the losses was type "Mittel-U class" (the biggest and the strongest German submarines in the Mediterranean). Naturally, the Allies’ anti submarine warfare was improved during the war. Also, the Allies organised maritime traffic in convoys. Because of improvements of the Otranto barrage it was getting more difficult for German submarines to get from the Adriatic Sea into the Mediterranean Sea. Finally, from 1917 in the war against German submarines in the Mediterranean Sea were involved also the US Navy and the Imperial Japanese Navy. In April of 1917, ships of the Japanese Navy were sent to the Mediterranean Sea, one cruiser and three divisions of destroyers.

End of German U-boat arm in the Mediterranean
At the end of WWI (in the Adriatic) German submarines in the Adriatic Sea that had any mechanical problems and thus were unable to return to Germany by sea were destroyed (blown up) by their own crews. Those days Germans destroyed in Pula, Rijeka, Trieste and Kotor their submarines as follows: U 47 and U 65, U 72, U 73, UB 48, UB 129, UC 25, UC 34, UC 53 and UC 54.

The German Army units, German shipyard workers and German Navy sailors left Pula by train on 26-28th October 1918.

On 28 October 1918, 15 German submarines left the Adriatic Sea and went to Germany by sea, via the Straits of Gibraltar (U 34, U 35, U 38, U63, UB 49, UB 50, UB 51, UB 105, UB 128, UC 20, UC 22, UC 27, UC 52, UC 67 and UC 73). 13 of the 15 submarines succeeded to get through to German ports. During the return to Germany, U34 sank by Q-ship "Privet" on 9th November 1918, in the vicinity of Gibraltar. U 35 was interned in Spain (Ferrol), then the submarine surrendered to France. After that, the submarine was given to Britain and was finally scuttled.

After four years of the war and in the moment when defeat was obvious and unavoidable, German submariners had enough perseverance to undertake such long and dangerous voyage. But the voyage turned out to be a waste of effort. In November of 1918 the Allies demanded the surrender of 160 German submarines (U-boats). According to the peace treaty Germany was forbidden to possess any submarines.

Effect of the German Navy submarines on revolutionary movements in the Austro-Hungarian Navy

The Austro-Hungarian armed forces were well equipped and prepared for the war. But the war lasted longer than they planned. Because of that, after two years of war, economic and other situation in the country became increasingly difficult. The Navy was also well prepared (better than the Army) but in the summer of 1917 and specially in 1918 working and living conditions in the Navy became extremely difficult like in the whole country. Quite simply, the sailors (i.e. the lower ranks) were hungry. The sailors knew very well that situation at their homes is same and even worse than in the Navy. Also, ex-prisoners of war, which were repatriated from Russian captivity, spread ideas of the Russian Revolution all around the Austro-Hungarian Armed Forces. Because of all mentioned, in the Navy started some revolutionary movements. The movements were stronger on older surface ships than on the new ones (modern battleships) and on the smaller naval units (destroyers, torpedo boats and submarines).

On 22nd January 1918 workers of the Navy shipyard (Arsenal) in Pula started with general strike. At that moment in Pula were also some units of the German Army (land forces), about 30 German submarines based in Pula, with about 500 members of the German Navy. About 1500 German workers from Kiel were in Pula. They worked in the Navy shipyard in Pula (maintaining of German submarines and assembling of the submarines that were came in Pula by train). German workers joined the strike. But, units of the German land forces helped the Austro-Hungarian Navy leadership against strikers. Those days (starting with 5th February 1918) many German Army patrols were seen on the streets in Pula. German sailors were neutral during the strike, especially submariners. The submarines’ officers had completely control on their crews. Also, Germans used anchored old Austro-Hungarian cruiser "Maria Theresia" as the flotilla base. German sailors were separated from their Austro-Hungarian colleagues. It is relevant that German submariners (even lower ranks) had much better living conditions (accommodation and food) than their Austro-Hungarian colleagues. In such situation it was normal that German submariners couldn’t to join the revolutionary movements.

On 1st February 1918 sailors onboard the Austro-Hungarian surface ships in Kotor mutinied. The rebel-sailors asked for better conditions and for break of the war. The mutiny was stronger onboard the oldest surface ships which were in Kotor, and much weaker onboard smaller surface units (destroyers and torpedo boats). At that moment, just three German submarines were present in Kotor, together with their base ship, anchored ship "Cleopatra".

The German officers had good control on their crews and, like in Pula, the German sailors were separated from Austro-Hungarian sailors and lived in much better conditions. Some days after the mutiny started, the German submarines (along with the Austro-Hungarian land forces) helped the Austro-Hungarian authorities against rebel-sailors. During the mutiny, the Austro-Hungarian leadership in Kotor sent following message: "It is necessary to take all measures to make impossible for the fleet to escape (to Italy). It is better to sink the fleet. And because of that, in the last case, German submarines must be called."


There were many battlefields around the Mediterranean Sea in the WWI. Balkan, Italy, Turkey (Dardanelles), Palestine (of that time) etc. It was vital for the Allies to ensure safe maritime traffic to and around all the battlefields. Also, the Allies had important maritime traffic lines through the Mediterranean Sea. For example, France had colonies on the Northern African coast. So, they had also colonial troops in those countries and they had to transport them to the Western front (in France). Great Britain had to transport troops from the Far East and from Australia to the France and Great Britain (via the Suez Canal). Also, they had to transport troops from Egypt to Gallipoli (within the Dardanelles’ operation) and lately to Balkan. In 1918 British transported their troops frequently from the Mediterranean war theatre to the Western front (France). Because of all mentioned Germans sent their submarines in the Mediterranean. But, they send the submarines not just to obstruct and to endanger the Allies’ maritime transport but also to make an impact on other members of the Central Powers, Austria-Hungary, Turkey and Bulgaria. Austro-Hungarian submarines operated mainly in the Adriatic Sea and successfully limited operations of the Allies’ big warships in the Adriatic Sea. German submarines operated in the Mediterranean Sea (against the Allies’ maritime transport) and in the Aegean Sea and the Black Sea (within the Dardanelles’ operation). The German submarines were based in Pula, Kotor and Istanbul. German submarines that operated against the Imperial Russian Navy warships (in the Black Sea) were stationed in Bulgarian harbours Burgas and Varna.

The German submarines, which served in the Mediterranean Sea, could to base in just few ports. In Turkey, possible submarine bases were just in Istanbul and in Turkish ports in the Black Sea. But, the allied naval forces in the front of Dardanelles blocked those submarines (and German/Turkish surface ships). Turkish coast in the Mediterranean Sea is long but the Turkish Navy was weak and wasn’t able to ensure safety of the Turkish (Mediterranean) coast from the Allies’ naval attack. Because of reasons mentioned above there were just two safe bases for the German submarines which operated in the Mediterranean Sea, Pula (the Northern Adriatic) and Kotor (the Southern Adriatic). Another problem for the German submarines in the Mediterranean was that there was just one shipyard in which they could be repaired completely. It was the Austro-Hungarian Navy shipyard in Pula. The shipyard in Pula was good equipped and had qualified engineers and workers. During the war workers from Germany were also sent to work on the submarines in the shipyard in Pula.

In order to stop German and Austro-Hungarian submarines’ penetration from the Adriatic into the Mediterranean and their return in the Adriatic, the Allies organised the Otranto barrage. Otranto is placed between the Adriatic and the Ionian Sea, line from Italy to Albania. The British Royal Navy established the barrage on 26th September 1915 as a system of underwater barriers (fishing nets and anti submarine mines); observations by aeroplanes, patrolling by surface ships etc. In 1916 the French Navy and the Italian Navy joined into the barrage operations. In 1917 the US navy as well joined the barrage operations at Otranto. During the war the barrage was improved, but the barrage only made the penetration of German submarines from the Adriatic into the Mediterranean Sea more difficult. The barrage never completely stopped passing of the German submarines.

Germans submarines forced the Allies to change their strategy of naval warfare and marine traffic in the Mediterranean Sea. During the war the Allies had to organise convoys, which was more complicated and slower than ordinary maritime traffic. In 1916 British maritime traffic from Australia and from the Far East had to be directed around South Africa instead of through the Mediterranean Sea (via the Suez Canal). The Central Powers submarines in the Mediterranean Sea sank about 35 % of the whole Allied tonnage that was sunk during WWI.

On 27th May 1915 Italy joined the Entente. The joining changed the Central Powers strategy in the Mediterranean Sea. But the submarine warfare for Austro-Hungarian and German submarines became easier because from that moment almost all ships in areas of their operations (the Adriatic Sea, the Mediterranean Sea and the Aegean sea) were under enemies’ (i.e. the Allies’) flags. So, the Central Powers submarines hadn’t potential problems with neutral ships.

On 31st August 1916 and on 9th January 1917 there were two conferences in Germany about unrestricted submarine warfare. On the both conferences were present the Imperial Chancellor, Dr. Von Bethmann-Hollweg, and German military leadership. On the both conferences the military leadership reported that Germany is able just to keep situation of defence. Also, the leadership reported about successful blockade of Germany, by the Allies. Because of all above mentioned, the leadership asked for permission for unrestricted submarine warfare, from 1st February 1917. The situation was so bad for Germany, that they were ready even for involvement of the USA and other neutral countries in the war (on the Allies’ side, naturally). The Imperial Chancellor Dr. Von Bethmann-Hollweg said (on 9th January 1917): "The U-boat war is the last card."

German leaders knew importance of submarine warfare in the Mediterranean Sea. During the war one quarter of new-built submarines were sent to the Mediterranean Sea. Also, German submarines which operated in the Mediterranean Sea received their orders directly from the Naval Staff in Berlin and not from the Fleet. In spite of all that Germans simply hadn’t enough submarines to completely defeat the Allies naval forces and to completely interrupt the Allies’ maritime traffic.

On 3rd November 1918 the Italian Navy Command asked leadership of the former Austro-Hungarian Fleet in Pula about presence of German submarines in the Adriatic Sea. The Austro-Hungarian Navy and the Fleet was collapsed (as well as the whole Austro-Hungarian Empire) and Italians didn’t care about possible threat, but Germany was still in the war and German submarines could threaten Italian efforts to take control of the eastern Adriatic coast. The leadership from Pula answered that the German submarines had left the Adriatic Sea few days ago. After that, nothing could stop Italy to take control of Pula, the whole Istrian peninsula and some parts of the eastern Adriatic coast and islands. This event shows for the best influence of the German Navy Mediterranean Submarine Flotilla on the Central Powers war efforts in the Mediterranean Sea.

Just some details about the Central Powers’ submarine warfare were mentioned in this article. There were much more events. For example, the first submarine sank by aeroplanes was French submarine "Foucault" (397 t). The submarine was sank by the Austro-Hungarian Navy aeroplanes (hydroplanes) "L132" and "L135", on 15th September 1916.

During the war Italy lost two battleships because of Austro-Hungarian sabotages. Italian battleship "Benedetto Brin" (13400 t) sank in the port of Brindisi on 30th September 1915. Also, Italian battleship "Leonardo da Vinci" (23000 t) capsized in the port of Taranto on 2nd August 1916, because of explosion. How the saboteurs came on the places? It is most likely that they came by means of submarines.

In this article names of towns are given in two languages, Croatian and Italian languages- Pula (Pola), Rijeka (Fiume) and Kotor (Cattaro). This is because in books and other sources you can find one of the names, in Croatian or Italian version. Both versions are suitable and equal.

This article was published on 14 Jan 2006.

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