The Central Powers submarines in the Mediterranean during WWI

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

• U12 on 21st December 1914 heavily damaged French dreadnought "Jean Bart" (torpedo into the ship’s bow).
• U26 (German UC14, under Austro-Hungarian flag) on 7th July 1915 sank Italian armoured cruiser "Amalfi", in the front of Venezia.
• U4 on 18th July 1915 at dawn sank Italian armoured cruiser "Giuseppe Garibaldi", in the vicinity of Dubrovnik.
• U4 on 9th June 1915 torpedoed and heavily damaged British light cruiser "Dublin".
• U5 on 27th April 1915 at dawn sank (by two torpedoes) French armoured cruisers command ship "Leon Gambetta", South of cape Santa Maria di Leuca.
• U5 on 5th August 1915 sank Italian submarine "Nereide", in the vicinity of island Palagruza.
• U6 on 18th March 1916 sank French destroyer "Renaudin", in the vicinity of Durres (Albania).
• U5 on 8th June 1916 sank Italian transport ship "Principe Umberto", on the ships way to Valona.
• U15 on 25th June 1916 sank Italian auxiliary cruiser "Citta di Messina" and French destroyer "Fourche", in the Strait of Otranto.
• U16 on 16th October 1916 sank Italian destroyer "Nembo", in the vicinity of the Strait of Otranto.
• U17 on 10th July 1916 sank Italian destroyer "Impetuoso".
• U27 on 11th June 1917 damaged Japanese destroyer "Sakaki".
• U27 on 24th May 1918 sank British destroyer "Phoenix".
• U47 on 20th September 1918 sank French submarine "Circe".
• U31 on 2nd October 1918 damaged British cruiser "Weymouth".

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

• U3 sank on 13th August 1915, by French destroyer "Bisson", 7 crewmembers died 14 rescued and captured.
• U6 sank on 13th May 1916, entangled in the Otranto barrage’s net, destroyed by British drifters "Dulcie Dorry" and "Evening Star II", the crew rescued and captured.
• U12 sank by mine on 8th August 1915, during ambush in the front of Venezia.
• U16 on 11th October 1916 in the vicinity of Valona (Albania) attacked one convoy and sank Italian destroyer "Nembo", but sank by steam ship "Bormida" (same convoy, the steam ship crushed the submarine), two NCO’s died, the rest of the crewmembers rescued and captured.
• U20 sank on 15th July 1918 by Italian submarine "F12", at the mouth of river Tagliamento, all crewmembers died.
• U23 sank on 21st February 1918 near Valona by Italian torpedo boat "Airone", all crewmembers died.
• U30 missed in action during her first action, probably sank by mine in the Otranto barrage on 1st or 2nd April 1917.

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.