Frederick Leslie Sayers enlisted in the Australian Imperial Forces on 13 February 1915, and joined the 6th Reinforcement of the 10th Light Horse Regiment four months later. They were deployed to Cairo, on the 25 June 1915. After fighting in Gallipoli his unit was evacuated on the 13 December 1915. After joining the 3rd Light Horse Machine Gun Squadron, he was involved in a number of minor battles, and in 1916 was involved in the capture of El Arish, he was with the Squadron throughout 1917. After been diagnosed with debility he was discharged in January 1919, but remained attached to the administration section of the Central Training depot until he returned to the 3rd Light Horse Australian Machine Gun Squadron. He returned to Australia on the 10 July 1919.