William was born at Inverell and worked as a Coachsmith having served a five year apprenticeship with coach builder Mr. Cusick. He was a keen Rugby Union player for the Inverell Imperial Football team. When he enlisted on 19 August 1915, he was 20 years old and had been a member of the 5th Light Horse at Inverell for eighteen months.
As a Private with the 3rd Battalion 14th Reinforcements, he left Australia on board RMS Osterley on 15 January 1916. A few months after arriving in France, he transferred to the 1st Pioneer Battalion. During 1917 he suffered Trench Fever which resulted in his evacuation to hospital in England. He eventually returned to France but became ill with influenza and was invalided back to England. As William was in poor health he was returned to Australia in December 1918.
Private Brew's name is recorded on the Inverell Honor Roll.