William Davis was 45 years old when he enlisted. He was a single man, a dentist with a Doctor of Dentistry qualification from the University of California, USA. He already had extensive military experience, as a Lieutenant with the 63rd and 62nd Infantry, as well as the Automobile Corps. and had been elevated to Captain on 1 January, 1914. He declared in his attestation papers that he had no civil employment, but was attached to to the Royal Park Camp in Carlton, where he presumably practised. Initially, he gave his next of kin as his brother, Ernest L. Davis, but on his enlistment form of 6 March, 1916, he had changed this ot his sister, Mrs. Rachel Abraham, living at 15 Landsdowne St., East Melbourne, which he also gave as his own postal address.

Following enlistment, he was attached to the 39th Battalion with the rank of Captain. The battalion left Melbourne on  board HMAT  'Ascanius' A11 on 27 May, 1916. They disembarked on 18 July at Devonport, England. William Davis was almost immediately ill with lumbar myalgia and was transfeered to Fargo Military Hospital on 15 August. It must have been fairly severe, because he was not discharged until 18 October. From hospital, the decision was made that he should stay in England and he was seconded to the 10th Training Battalion on 30 September, 1916. However, he was again admitted to Fargo Hospital on 8 December, this time with rheumatism.

He was discharged on 22 December and from there transferred to the No.1 Command Depot and placed on Court Martial work. On 2 September, he was transferred to Wareham and stayed there until March 3, 1917, when he was admitted to hospital with V.D. He spent 66 days in hospital, returning to duty on 20 May, this time in Tidworth. From there, he was sent to Adminstrative Headquarters in Codford,before being returned home to Australia. On 27 July, 1917, he was discharged from further service due to rheumatism and gout,  leaving England on board the A71 'Nestor'. His appointment was officially terminated on 24 November, 1917, but on 1 Januar, 1919, he was appointed Junior Assistant Censor, transferred from the 62nd Infantry to Reserve of Officers 3rd Military District. In 1931, he was placed on the retired list. 

William Davis does not appear to have married. He died on 13 September, 1950.