Battle of the Strait of Otranto ( 1917 ) The 1917 Battle of the Strait of Otranto was the result of an Austro - Hungarian raid on the Otranto Barrage , an Allied naval blockade of the Strait of Otranto . The battle took place on 14 – 15 May 1917 , and was the largest surface action in the Adriatic Sea during World War I . The Otranto Barrage was a fixed barrier , composed of lightly armed drifter s with anti - submarine nets coupled with minefields and supported by Allied naval patrols . The Austro - Hungarian navy planned to raid the Otranto Barrage with a force of three light cruisers and two destroyers under the command of Captain Miklós Horthy , in an attempt to break the barrier to allow U - boats freer access to the Mediterranean , and Allied shipping . An Allied force composed of ships from three navies responded to the raid and in the ensuing battle , heavily damaged the Austro - Hungarian cruiser . However , the rapid approach of the Austro - Hungarian relief force persuaded Rear Admiral Acton , the Allied commander , to retreat . Disposition of forces . Under the command of Horthy , three Austro - Hungarian cruisers : " Novara " , " Saida " , and " Helgoland " , modified to resemble large British destroyers , were to attack the drifters on the night of 14 May and attempt to destroy as many as possible before daybreak . The destroyers " Csepel " and " Balaton " were to mount a diversionary raid off the Albanian coast in order to confuse any Allied counter - attack . Two Austro - Hungarian U - boats — and , along with the German U - boat — were to participate in the operation as well . A supporting force composed of the armored cruiser , two destroyers , and a number of torpedo boats was on standby if the raiders ran into trouble . The old pre - dreadnought battleship " Budapest " and a screen of torpedo boats were also available if necessary . An Allied destroyer patrol was in the area on the night of 14 May , to the north of the Barrage . The Italian flotilla leader " Mirabello " was accompanied by the French destroyers " Commandant Rivière " , " Bisson " , and " Cimeterre " . The Italian destroyer " Borea " was also in the area , escorting a small convoy to Valona . A support force was based in the port of Brindisi , consisting of the British cruisers " Dartmouth " and " Bristol " and several French and Italian destroyers . Raid on the drifters . The Italian convoy escorted by " Borea " was attacked by the Austro - Hungarian destroyers " Csepel " and " Balaton " at approximately 03 : 24 . The Austro - Hungarians sank " Borea " and a munitions ship , and a second was set on fire and abandoned . The three cruisers were able to pass through the line of drifters , and at 03 : 30 began attacking the small barrage ships . The Austro - Hungarians frequently gave the drifter crews warning to abandon ship before opening fire . In some instances , the drifter crews chose to fight : " Gowan Lee " returned fire on the Austo - Hungarian ships . The ship was heavily damaged , but remained afloat ; her captain — Joseph Watt — was later awarded the Victoria Cross for his actions during the battle . There were 47 drifters in Barrage on the night of 14 May ; the Austro - Hungarians managed to sink 14 drifters and damage four more . The lack of sufficient Allied escorts forced the withdrawal of the remaining blockading ships , although only for a short time . Battle . By this time , the Allied naval forces in the area were aware of the raid , and were in a position to block the Austro - Hungarian retreat . Rear Admiral Alfredo Acton — the commanding officer of the Italian Scouting Division — ordered " Mirabello " s group southward at 04 : 35 , while he embarked on the British light cruiser . By 06 : 45 , the cruisers " Dartmouth " and — along with the Italian destroyers " Mosto " , " Pilo " , " Schiaffino " , " Acerbi " , and " Aquila " — were sailing north in an attempt to cut off the Austro - Hungarian cruisers . The Italian light cruiser " Marsala " , the flotilla leader " Racchia " , and the destroyers " Insidioso " , " Indomito " , and " Impavido " were readying to sail in support as well . The " Mirabello " group engaged the Austro - Hungarian cruisers at 07 : 00 , but were heavily outgunned , and instead attempted to shadow the fleeing cruisers . At 07 : 45 , Rear Admiral Acton ' s ships encountered the destroyers " Csepel " and " Balaton " . After 20 minutes , the Italian destroyers were able to close the distance to the Austro - Hungarian ships ; the two groups engaged in a short artillery duel before a shot from " Csepel " struck " Aquila " and disabled the ship ' s boilers . By this time , the Austro - Hungarian destroyers were under the cover of the coastal batteries at Durazzo , and were able to make good their escape . At 09 : 00 , " Bristol " s lookouts spotted the smoke from the Austro - Hungarian cruisers to the south of her position . The Allied ships turned to engage the Austro - Hungarian ships ; the British ships had both a superiority in numbers and in firepower ; " Dartmouth " was armed with eight guns and " Bristol " had two 6 inch and ten , compared to the nine guns on each of the Austro - Hungarian ships . Unfortunately for the Allies , their numerical superiority was quickly lost , as their destroyers were either occupied with mechanical problems , or protecting those destroyers suffering from breakdowns . The support forces of both sides — the " Sankt Georg " group for the Austro - Hungarians , and the " Marsala " group for the Allies — were quickly dispatched to the battle . " Dartmouth " — faster than " Bristol " — closed to effective engagement range with the Austro - Hungarian ships , and opened fire . A shell from " Dartmouth " struck " Novara " , at which point the Austro - Hungarian ships laid a smoke screen in order to close the distance . " Dartmouth " was struck several times , and by 11 : 00 , Acton ordered the ship to reduce speed to allow " Bristol " to catch up . " Novara " was hit several more times , and her main feed pumps and starboard auxiliary steam pipe had been damaged , which caused the ship to begin losing speed . At 11 : 05 , Acton turned away in an attempt to separate " Saida " from " Novara " and " Helgoland " . At this point , " Sankt Georg " was approaching the scene , which prompted Acton to temporarily withdraw to consolidate his forces . This break in the action was enough time for the Austro - Hungarians to save the crippled " Novara " ; " Saida " took the ship under tow while " Helgoland " covered them . Unaware that " Novara " had been disabled , and fearing that his ships would be drawn too close to the Austrian naval base at Cattaro , Acton broke off the pursuit . The destroyer " Acerbi " misread the signal , and attempted to launch a torpedo attack , but was driven off by the combined fire of the " Novara " , " Saida " , and " Helgoland " . At 12 : 05 , Acton realized the dire situation " Novara " was in , but by this time , the " Sankt Georg " group was too close . The " Sankt Georg " group rendezvoused with " Novara " , " Saida " , and " Helgoland " , and " Csepel " and " Balaton " reached the scene as well . The entire group returned to Cattaro together . At 13 : 30 , the submarine " UC - 25 " torpedoed " Dartmouth " , causing serious damage . The escorting destroyers forced " UC - 25 " from the area , but " Dartmouth " had to be abandoned for a period of time , before it could be towed back to port . The French destroyer " Boutefeu " attempted to pursue the German submarine , but struck a mine laid by " UC - 25 " that morning and sank rapidly . Aftermath . As a result of the raid , it was decided by the British naval command that unless sufficient destroyers were available to protect the barrage , the drifters would have to be withdrawn at night . The drifters would only be operating for less than twelve hours a day , and would have to leave their positions by 15 : 00 every day . Despite the damage received by the Austro - Hungarian cruisers during the pursuit by " Dartmouth " and " Bristol " , the Austro - Hungarian forces inflicted more serious casualties on the Allied blockade . In addition to the sunk and damaged drifters , the cruiser " Dartmouth " was nearly sunk by the German submarine " UC - 25 " , the French destroyer " Boutefeu " was mined and sunk , and a munitions convoy to Valona was interdicted . However , in a strategic sense , the battle had little impact on the war . The barrage was never particularly effective at preventing the U - boat operations of Germany and Austria - Hungary in the first place . The drifters could cover approximately apiece ; of the - wide Strait , only slightly more than ½ was covered . The raid risked some of the most advanced units of the Austro - Hungarian fleet on an operation that offered minimal strategic returns .