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.

[7][8][9] After being relieved by Linienschiffsleutnant Franz Rzemenowsky von Trautenegg from late March to early May 1916, Fähndrich resumed command on 10 May.

[4] 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.

[10][Note 2] 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 tons).

The escorting destroyer Fourche began a depth charge attack on U-15 and assumed success when an oil slick appeared on the surface.

[13] On 25 October, U-15, back under the command of von Trautenegg,[4] sank the 2,207 GRT Italian steamer Polcevera,[14] a sister ship to Stura (sunk by U-15 in May).