Sidney enlisted at Inverell in December 1915 stating he was a twenty four year old Share Farmer who was born at Fakenham, Norfolk, England. He had been a member of the Myall Creek Rifle Club for twelve months and gave his Australian address as ‘Kurrajong’ Delungra NSW.
He joined the 33rd Battalion, C Company and departed Australia on HMAT A74 Marathon in May 1916, arriving in England two months later. After further training he was sent to France in November. The following year he was severely wounded in July, transferred to England and admitted to Edmonston Military Hospital with a gunshot wound to his knee, leg and thigh.
Sidney was returned to Australia and medically discharged in August 1918. His name is inscribed on the Inverell and Delungra Honor Rolls and on the new Anzac memorial at Delungra Park.