SM U - 15 ( Austria - Hungary ) SM " U - 15 or U - XV " was a or U - boat of the Austro - Hungarian Navy ( ) during World War I . " U - 15 " was constructed in Germany and shipped by rail to Pola where she was assembled and launched in April 1915 . She was commissioned in October 1915 . " U - 15 " was the most successful boat of the " U - 10 " class , sinking six ships totaling more than . The boat survived the war and was handed over to Italy as a war reparation and scrapped in 1920 . Design and construction . " U - 15 " was constructed at AG Weser in Bremen for the Austro - Hungarian Navy and then shipped by rail in sections to Pola , where the sections were riveted together . Though there is no specific mention of how long it took for " U - 15 " s sections to be assembled , a sister boat , the German Type UB I submarine " UB - 3 " , shipped to Pola from Germany in mid - April 1915 , was assembled in about two weeks . " U - 15 " was launched in April . " U - 15 " was a small , coastal submarine that displaced surfaced and submerged . She featured a single shaft , a single Daimler diesel engine for surface running , and a single electric motor for submerged travel . " U - 15 " was capable of up to while surfaced and while submerged at a diving depth of up to . She was designed for a crew of 17 officers and men . " U - 15 " was equipped with two torpedo tubes located in the front and carried a complement of two torpedoes . In October 1916 , " U - 15 " s armament was supplemented with a 37 mm / 23 ( 1 . 5 in ) quick - firing ( QF ) gun . This gun was replaced by a 47 mm / 23 ( 1 . 9 in ) QF gun in November 1917 . Operational history . SM " U - 15 " was commissioned into the Austro - Hungarian Navy on 6 October under the command of " Linienschiffsleutnant " Friedrich Schlosser . On 28 November , " Linienschiffsleutnant " Friedrich Fähndrich was assigned to the first of two stints in command of the boat . On 18 December , Fähndrich and " U - 15 " attacked and sank two Albanian sailing vessels near Lezhë . The " Erzen " , of , and the " Figlio Preligiona " , of , were both sunk at position . After being relieved by " Linienschiffsleutnant " Franz Rzemenowsky von Trautenegg from late March to early May 1916 , Fähndrich resumed command on 10 May . One week later , on 17 May , " U - 15 " torpedoed and sank the Italian steamer in the Adriatic some east of Brindisi . The following month , Fähndrich and the crew of " U - 15 " scored their second double kill when they sank the Italian auxiliary cruiser ( ) and the French destroyer " Fourche " ( ) . While about east of Otranto on 23 June , " U - 15 " torpedoed and sank " Cittá di Messina " . The escorting destroyer " Fourche " began a depth charge attack on " U - 15 " and assumed success when an oil slick appeared on the surface . After the captain of " Fourche " turned his attentions to the rescue " Cittá di Messina " s survivors , " U - 15 " launched a single torpedo that struck " Fourche " amidships and sank her . On 25 October , " U - 15 " , back under the command of von Trautenegg , sank the Italian steamer , a sister ship to " Stura " ( sunk by " U - 15 " in May ) . " Polcevera " was the last ship sunk by " U - 15 " . From October 1916 to the end of the fighting in November 1918 , " U - 15 " s activities are unknown . " U - 15 " was at Pola at the end of the war when Austria - Hungary handed her over to Italy . " U - 15 " was scrapped at Pola by 1920 .