Thomas entered the war in the Balkans on 9th July 1915. He is mentioned in a list of men who went with Lt Smith and a party of stretcher-bearers to collect wounded between Green Knoll and The Pimple, Suvla on 17th August 1915. He was originally listed as missing but was later determined to have been killed that day. In his book ‘At Suvla Bay’, John Hargrave’s describes the disappearance of the party and makes a reference to Thomas Mellor:- “Early that morning they had formed up, and gone off under Lieutenant S--- along the mule track overlooking the Gulf of Saros. That was all. There was still hope, of course...but there wasn't a sign of them to be seen. The machine gun section had seen them pass right along. Some officers had warned them not to go up, but they went and they never came back... We supposed that the young officer, coming fresh to the place, did not know where the British lines ended and the Turks’ began, and he marched his squads into that bit of No Man’s Land beyond the machine-gun near ‘Jefferson's Post,’ and was either shot or taken prisoner. It made the men heavy and sad-minded. ‘Poor old Mellor - ‘e warn't a bad sort, was he!’”