Enlisted in December 1915. Evenwood's Hey Day by Elsie Anderson et al states that he was assigned to the Royal Veterinary Corps, which seems likely given the mention of horses - see letter below). He presumably was subsequently transferred to the Royal Field Artillery Regiment (newmp.org.uk and the Absent Voters' List) .
William wrote to the local Vicar in February 1916 saying he was in a hospital camp after smashing a finger on his left hand as the result of an accident at a rail head in France and of being sorry he could not get into a fighting unit. He described the risk to the men in France from the many frisky horses passing through the camp and the consequent need to be alert, of not knowing where he was stationed and of the beauty of the countryside. The hospital and camp were not finished and they were living under canvass.