In the early hours of 23rd February 1916, heading back to the UK after carrying more troops to Mudros in the Gallipoli Campaign, Olympic was sighted by the German submarine U35. The Officer of the Watch ordered the liner to alter course, and the fo’castle gun fired several shots, none of which came close to the submarine. Some reports claim an attack was carried out by the submarine but was unsuccessful. The submarine captain’s log, however, claimed conditions were bad and he didn’t press home an attack.
Only a few days earlier, while at Mudros, Olympic had been attacked by an enemy aircraft, believed to have taken off from an aerodrome in Bulgaria. This attack was beaten off by escorting warships, and the aircraft was later downed by British fighters from Imbros. Olympic arrived back at Liverpool on 13th March, having carried over 25,000 troops to Gallipoli in just four trips.