Abott Halford John McQuinn joined up to the military on 29 June 1918. He claimed to be 21 years and 4 months old and born on 25 February 1897 in Sydney, though his birth was also recorded as Launceston, Tasmania  in 1892. He was the son of John Jacob Wallace McQuinn and his wife Florence Evelyn, nee Abbott. Throughout his life, he used various versions of his name. He married Jessie Amelia Grace McCurdy on 1 July 1913, using the name William Henry Abbott McQuinn. This makes the Launceston date of birth more probable, given that he would have been only 16 if born in 1897. Their first child, a son, Wallace Selwyn , was born on 1 July, 1913, while their daughters, Jean Margaret was born in 1917 and Rosabel Elaine in 1919. 

Abbot Halford, known as Harry, also claimed to be an Electrical and Mechanical Engineer, who had completed a 5 year apprenticeship with the Launceston Corporation. He was sent to  the Broadmeadows  Recruitment Depot and placed with the 16th Reinforcements. On 7 November, 1918, he was promoted to Lance Corporal. He embarked for the war on S.S. Carpentaria on 7 November, 1918, only five days before the Armistice was declared. and on 24 February, 1919, was discharged 'in consequence of demobilization'. His record shows that, prior to his return to Australia, he had served 180 days, 35 days abroad. 

In 1919, he and Jessie were living at 87 Rathmines Rd, Fairfield and was also listed in the Australian City Directories as  at 35 Greeves St., St Kilda, probably his business. 

In 1919, he sent a letter to the military authorities asking for his discharge certificate, as he was leaving Victoria for another state. At this time, he was living at 35 Austral Avenue, West Brunswick, with his wife Jessie and working as a salesman. He was also listed in the 1924 Electoral Roll as living as 274 St Kilda Rd., occupation 'Motor Expert'.  Jessie was not registered.   In 1926, he was picked up by the police at Albury and charged with 'deserting his wife, Jessica Amelia Grace McQuinn'.

In 1931, the Electoral Rolls had him living a 'Summerlands', Alexandra, Victoria,  and from 1934-1937 at Webster St., Alexandra as a Radio Engineer. By the late 1930s, he had once more changed his name, this time to John Wallace, and became a writer of mystery stories. In 1938 he was living in Dandenong, but about to do a tour of all the Australian states, both to sell his latest book and to gather material for new books. In all, he appears to have written twelve books: Millionaire Gangster (19370; The Sedan Murder (1938); Beauty Wins (1939); Vengeance of - (1939) Rubicon Outlaws (1939); Dead 'un Wins (1940); It's Here (1940). Writing as Texas Ranger, he also wrote Cross B (1940) and Trail Outlaws (1939).  A second pseuonym was Gerald Grantham, under which name he wrote The Dope Runners and The Mystery of the S.S. Timor, both in 1940.

An article in The Argus of 30 September, 1938, comments

Mr Wallace is a conscientous novelist, who never writes about places unless he knows about them from personal observation'. 

In the same year, the Benalla Ensign of 18 November 1938, under the title, Literary Visitor observes

Since he left his native Tasmania he has wandered about the world and been responsible for 37 thrillers ... he writes to the tune of 12-16 books per year, which takes him various periods up to a month to write'.

On 7 July 1943, the Dandenong Journal reported that John Wallace had decided to stand for Parliament as a non-party candidate for the Electorate of Flinders. However, on 28 July, the Journal reported Wallace as deciding not to stand: As it is impossible for Mr John Wallace, well known Dandenong author, to obtain the services of any competent person to look after his many interests, he has decided not to stand for Flinders in the Federal election. 

Due to his changes of name, it is difficult to track him through the Electoral Rolls. He died at Heidelberg, probably the Repatriation Hospital. Jessie died on 17 October, 1935 and was buried at the Melbourne General Cemetery.