Henry Matthew Wallis was born in Ballarat and was a Labourer when he enlisted in the 38th Battalion, 7th Reinforcement on 10 January 1917 at the age of 18. His unit embarked from Melbourne, Victoria, on board HMAT A70 Ballarat on 19 February 1917 and disembarked at Devonport, England, on Anzac Day, April 25th, 1917. He marched in to the 10th Training Battalion where he was employed in the Officers' Mess, and it was not until October 24th 1918 that he joined the 38th Battalion in France. He returned home on the Karagola and disembarked at Melbourne on June 12th 1919.
He had two brothers that also served: Driver Charles Wallis, 5th Divisional Train, returned to Australia, 8 May 1919. (Tree No. 3496); Private William Gordon Wallis, 29th Battalion, returned to Australia, 22 March 1917. (Tree No. 3494)
Tree No. 3498