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 2,237 Italian steamer SS Stura 2 in the Adriatic some 18 nautical miles east of Brindisi.