Collinson joined the Lancashire Fusiliers of the British Army at age 15 in 1889 and stated his age was 18. He was transferred to the reserve in 1895, but was recalled to rejoin the Fusiliers in November 1899 and saw action at Spion Kop and Ladysmith during the Second Boer War. Collinson was honourably discharged in April 1902 and by 1911, he was married with two children and working as a gas meter inspector. He re-enlisted in the Lancashire Fusiliers in Bury during the early months of the First World War and was sent to Gallipoli with his battalion in May 1915. Two days after his arrival, Collinson was wounded in action by rounds from an Ottoman heavy machine gun. A second lieutenant wrote of his wounding: