Mark Davis was the son of David  and Florrie Davis. He was born in East Melbourne, and his address may have been at 36 Clarendon St., East Melbourne, where his mother was living in 1903. He was a railway employee, married to Lillian May Davis, nee Fielding, in 1915. In 1916, when he enlisted he was 25 years and 4 months old. 

 Mark Davis enlisted on 3 March, 1916, and was sent for training at Royal Park, Mlebourne. From 18 February to 9 March, he was attached to the A/10th unit at Ascot Vale, then to the Australian Medical Corps, where he worked as a driver. On 18 April, he was on loand to the No. 11 Australian General Hospital at Royal Park, where he stayed until 6 October.

His record was not good: on 23 August, he was fuond guilty of using obscene language, resisting arrest, assaulting a policeman and refusing to show his leave pass. On 4 October, he went AWL for a day. Atfer this, he was sent back to camp, to serve with the AMC again in K Company 2nd Depot Battalion. However, on 16 October, he was again AWL from 1st Parade at the Australian Clearing Hospital in Royal Park. On 19 October, he was placed in K Company, 2nd Battalion, but on 16 November, was moved to L Company. He remained with L Company, but at some stage was shifted to M company. He stayed in the army  10 January, 1917, when he went AWL and was not seen again.

A Court of Enquiry convened on 25 February,1917, examined the 'alleged illegal absence of No. 22027 Mark Davis, M Coy., 2nd Depot battalion'.  Witnesses confirmed that he 'was marked absent on 10/1/1917 and has not been so marked ever since.' As of 25 February, he had been absent for 44 days and had not returned his kit, valued at four pounds, six shilling and fivepence. 

Mark Davis enlisted again for World War 11, as a letter to his wife from 1957 noted, In her letter, Lillian Davis noted 'First was Enlisted for overseas service In Infantry transport  to AMC, then transferred back to Infantry in order to be sent overseas, but never got away. Secon enlisted as a transport driver ... discharged from Heidelberg Military Hospital through osteo-arthritis.' She was then paying five pounds a week in mortgage for her house, but could not afford it and he purpose of her letter was to ask for a War Service home. She was by then a widow, no deat notice could be found in Trove, nor was there an entry in the Death Index on Ancestry.com.au