Thomas William Kelly enlisted under the name William Thomas Kelly on 5 September 1916. He was the son of Martin Thomas Kelly and Hanora Kelleher. He was born in Queensland on 13 February 1892. He was 5′ 6 1/2, had blue eyes and brown hair. His occupation was a clerk.

He left Brisbane on 17 November 1916 aboard the Kyarra with the 47th Battalion of the 5th Division and arrived in Plymouth on 30 January 1917.

The 47th Battalion was raised in Egypt in 1916 as part of the expansion of the AIF following the Gallipoli campaign. It was decided that the AIF would be expanded from two divisions to four by splitting existing units to form the core and then supplementing with freshly-trained troops from Australia. The Battalion took experienced troops from the 15th Battalion and recruits from Queensland and Tasmania. It formed part of the 12th Brigade, which was attached to the 4th Division.

The Battalion was transferred to France and Belgium where it fought in the trenches of the Western Front for the next two and half years. During this time, it was in a number of significant battles, including the Battle of Pozières in 1916 and the Battles of Bullecourt, Messines and Passchendaele in 1917. In early 1918, the battalion was heavily involved in turning back the German advance during the Spring Offensive, taking part in the fighting that took place around Dernancourt.

The AIF fighting in France took a heavy toll on numbers and three brigades were ordered to each disband one of their battalions – the other two battalions disbanded at this time were the 36th and 52nd Battalions. This resulted in the 47th Battalion being disbanded on 31 May 1918. It had lost 661 men and 1,564 were wounded. The Battalion received 11 battle honours including a Victorian Cross.

Thomas moved into France on 19 March 1918. The Battalion played a role in turning the great German Spring Offensive by defeating attacks around Dernancourt during the last days of March and the first days of April 1918.

He returned to Australia 8 August 1919 aboard the “Milhades” and was living in Taringa when married in 1933.