text: sm u - 15 ( austria - hungary ) sm u - 15 or u - xv was a u - 10 - class submarine or u - boat of the austro - hungarian navy ( german : kaiserliche und königliche kriegsmarine or k.u.k. kriegsmarine ) 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 8 , 000 gross register tons ( grt ) . 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 125 . 5 long tons ( 127 . 5 t ) surfaced and 140 . 25 long tons ( 142 . 50 t ) submerged . she featured a single shaft , a single 59 bhp ( 44 kw ) daimler diesel engine for surface running , and a single 119 shp ( 89 kw ) electric motor for submerged travel . u - 15 was capable of up to 6 . 5 knots ( 12 . 0 km / h ; 7 . 5 mph ) while surfaced and 5 . 5 knots ( 10 . 2 km / h ; 6 . 3 mph ) while submerged at a diving depth of up to 50 metres ( 160 ft ) . she was designed for a crew of 17 officers and men . u - 15 was equipped with two 45 cm ( 17 . 7 in ) 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 , of 25 grt , and the , of 80 grt , were both sunk at position 41 ° 47 ′ n 19 ° 31 ′ e. after being relieved by linienschiffsleutnant franz von 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 2 , 237 grt italian steamer stura in the adriatic some 18 nautical miles ( 33 km ) 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 cittá di messina ( 3 , 495 grt ) and the french destroyer fourche ( 745 grt ) . while about 20 nautical miles ( 37 km ) 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 , sank the 2 , 207 grt italian steamer , a sister ship to stura ( sunk by u - 15 in may ) . 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 .