During World War I, E-15 served in the Mediterranean, participating in the Dardanelles campaign against Turkey. On April 16, 1915, under the command of Lieutenant Commander T.S. Brodie, E-15 left Mudros and attempted to break through the Dardanelles to the Sea of Marmara. Early in the morning of April 17, E-15 ran aground some ten miles in, under Kephaz Point. Fired on and disabled, Brodie and the crew were killed.
Several attempts were made to destroy E-15. First, British submarine B-6, with Brodie's brother on board, tried to sink her by torpedo, but missed. Later, during the night, destroyers Grampus and Scorpion (commanded by the future Admiral A.B. Cunningham of World War II Mediterranean Fleet fame), attempted to find her, but failed. The next morning, British submarine B-11 also failed to locate the beached E-15, then the battleships Triumph and Majestic (under intense fire themselves from shore batteries) fired on E-15 and missed. Meanwhile, seaplanes carried out their own failed attempts.
Finally, on the night of the April 18, one picket boat each from Triumph and Majestic, both armed with two 14-inch torpedoes, went in. Lieutenant Commander Eric Robinson in Triumph's boat commanded of the expedition; Lieutenant Godwin commanded Majestic's. Approaching E-15, Majestic's boat was stuck by gunfire, but managed to hit and destroy E-15 before sinking. Robinson rescued the crew and reached safety in Triumph's boat. This and other exploits in the Dardanelles earned Robinson the Victoria Cross.