Sing began his military career as part of the Australian and New Zealand Army Corps (ANZAC) forces in the Gallipoli Campaign in modern day Turkey. Biographer John Hamilton described the Turkish terrain thus: "It is a country made for snipers. The Anzac and Turkish positions often overlooked each other. Each side sent out marksmen to hunt and stalk and snipe, to wait and shoot and kill, creeping with stealth through the green and brown shrubbery ..." Sing partnered with spotters Ion 'Jack' Idriess and, later, Tom Sheehan. The spotter's task was to observe (spot) the surrounding terrain and alert the sniper to potential targets. Idriess described Sing as "a little chap, very dark, with a jet black moustache and goatee beard. A picturesque looking mankiller. He is the crack shot of the Anzacs."