U - 43 - class submarine ( Austria - Hungary ) The " U - 43 " class was a class of two coastal submarine s or U - boats operated by the Austro - Hungarian Navy ( ) during World War I . The two boats that comprised the class were Type UB II submarines of the Imperial German Navy , making the two classes identical . From the beginning of World War I , Austria - Hungary had been working to increase the size of its U - boat fleet , so the Imperial German Navy , which was finding it difficult to obtain trained submarine crews , sold two of its UB II boats , and , to its ally in June 1917 . The German Type UB II design incorporated improvements over Type UB I boats , the first coastal submarines of the German Imperial Navy . Among these were twin engines and shafts for more redundancy during operations , a higher top speed , and larger torpedo tubes with double the complement of torpedoes . As a result the UB II boats were nearly twice as heavy as their predecessor UB I boats . Both boats of the class were selected for German service in the Mediterranean while under construction . They were shipped via rail to Pola , assembled , launched , and commissioned in the German Imperial Navy , where both enjoyed great success against Allied shipping . In June 1917 , the boats were decommissioned , handed over to Austria - Hungary , and then commissioned into the Austro - Hungarian Navy in July . The " B " in the designation of both boats was dropped , but the submarines retained the same numbers , becoming " U - 43 " and " U - 47 " under the Austro - Hungarian flag . At the end of the war and were ceded to Italy and France , respectively , and had been scrapped by 1920 . Background . Austria - Hungary ' s U - boat fleet was largely obsolete at the outbreak of World War I . The Austro - Hungarian Navy satisfied its most urgent needs by purchasing five Type UB I submarines that comprised the from Germany , by raising and recommissioning the sunken French submarine " Curie " as , and by building four submarines of the that were based on the 1911 Danish " Havmanden " class . After these steps alleviated the most urgent needs , the Austro - Hungarian Navy had adopted the German Type UB II design for what became known as the Austro - Hungarian " U - 27 " class in mid 1915 , and had six of that class being built under license in Austria - Hungary by late 1916 . In November 1916 , Germany had inquired to find out if Austria - Hungary were interested in purchasing existing German submarines because Germany was having a hard time finding trained submarine crews . After protracted negotiations , which had stalled over the outflow of Austro - Hungarian gold reserves to Germany , an agreement to purchase two submarines — " UB - 43 " and " UB - 47 " — was reached in June 1917 . Design . The UB II design . The German UB II design of coastal submarines was a development from the design of the UB I boats , which had been originally ordered in September 1914 . During their trials , the UB I boats were found to be too small and too slow , but in - service use revealed another problem . The UB I boats had a single propeller shaft / engine combo such that if either component failed , the U - boat became almost totally disabled . The UB II boats featured twin propeller shafts and twin engines ( one shaft for each engine ) which not only alleviated this problem , but also had the added benefit of increasing the top speed . The new design also included more powerful batteries , larger torpedo tubes , and a deck gun . The UB II boats could also carry twice the torpedo load of their predecessors , and nearly ten times as much fuel . To contain all of these changes the hull was larger , and the surface and submerged displacement was more than doubled . The UB II boats were ordered from three manufacturers in groups that numbered between two and twelve . Each group had slight variations in design , resulting in differences in displacements , lengths , speeds , fuel capacities , and operational ranges . The " U - 43 " - class design . The " U - 43 " class consisted of two boats from a contracted group of six UB II boats built by AG Weser of Bremen . Like all of the UB II boats from different manufacturers and contract groups , the " U - 43 " group had distinct specifications . This group displaced surfaced and submerged . The boats had a single hull with saddle tank s ( an early style of ballast tank s ) , and were long with a beam of and a draft of . For propulsion , they featured two shafts , twin diesel engines of for surface running , and twin electric motors of for submerged travel . The boats were capable of while surfaced and submerged . The range of the boats was at surfaced , and at submerged . The " U - 43 " class boats were designed for a crew of 22 . The " U - 43 " class boats were armed with two bow torpedo tubes and carried a complement of four torpedoes . They were each equipped with an 88 mm / 26 ( 3 . 5 in ) deck gun and an machine gun . The two " U - 43 " - class U - boats were nearly identical to the eight boats of the Austro - Hungarian Navy ' s " U - 27 " class , which were built to UB II plans . Despite the similarities , the two groups are identified in sources as distinct classes . Construction . The six - boat group that included " UB - 43 " and " UB - 47 " was ordered in July 1915 , and both boats had been laid down in early September . This group was selected by the German Admiralstab for deployment to the Mediterranean , but , unlike the smaller UB I boats , they could not as easily be transported overland by rail . Weser prepared the boats for rail shipment by cutting the boat sections longitudinally , and sent all the materials , along with German shipyard workers , to Pola , where the boats were reassembled . " UB - 43 " was launched in early April 1916 , while " UB - 47 " followed in June . Class members . SM " U - 43 " . " UB - 43 " was ordered by the Imperial German Navy on 31 July 1915 and was laid down by AG Weser of Bremen on 3 September . While under construction , she was one of a group of six U - boats selected for service in the Mediterranean . " UB - 43 " was broken into railcar - sized components and shipped overland to the Austro - Hungarian port of Pola where Weser workers assembled her . She was launched on 8 April 1916 and commissioned into the Imperial German Navy as SM " UB - 43 " on 24 April , under the command of " Oberleutnant zur See " Dietrich Niebuhr . " Kapitänleutnant " Hans von Mellenthin was assigned to the boat in late August 1916 , and led the boat in sinking 19 ships ( ) over the next 8½ months . In April 1917 , von Mellenthin was replaced by " Oberleutnant zur See " Horst Obermüller who commanded the ship for the next three months , sinking three more ships ( ) and damaging the British cruiser . " UB - 43 " was decommissioned on 15 July and taken over by the Austro - Hungarian Navy . Renamed " U - 43 " for Austro - Hungarian service , the boat became the class leader of the " U - 43 " boats when she was commissioned into the Austro - Hungarian Navy on 30 July 1917 . The submarine ' s successes while under German command were not matched under Austro - Hungarian ; she damaged a single ship in November 1917 in her only successful attack . " U - 47 " was surrendered to France as a war reparation in 1920 and was broken up at Bizerta . SM " U - 47 " . " UB - 47 " was ordered by the Imperial German Navy on 31 July 1915 and was laid down at Bremen by AG Weser on 4 September . As one of six U - boats selected for service in the Mediterranean while under construction , she was broken into railcar - sized components and shipped overland to the Austro - Hungarian port of Pola . Shipyard workers from Weser assembled the boat and her five sisters at Pola , where she was launched on 17 June . SM " UB - 47 " was commissioned into the Imperial German Navy on 4 July 1916 under the command of " Oberleutnant zur See " Wolfgang Steinbauer . Steinbauer and " UB - 47 " sank 15 ships ( ) over the next nine months , including two Cunard Line steamers — and — serving as British troopship s , as well as the French battleship . Steinbauer also damaged three ships with a combined gross register tonnage of 16 , 967 . Under the command of Hans Hermann Wendlandt , who had replaced Steinbauer in April 1917 , " UB - 47 " sank an additional seven ships ( ) through 21 July , at which time the ship was decommissioned and handed over to the Austro - Hungarian Navy . The " B " in her designation was dropped when she was commissioned as SM " U - 47 " for the Austro - Hungarian Navy on 30 July 1917 . " U - 47 " s success under Austro - Hungarian command was less than that under the German flag ; only three ships ( ) were sunk through the end of the war . " U - 47 " was surrendered to France as a war reparation in 1920 and was broken up at Bizerta .