Leslie John Smith was born in Ballarat and was a Motor Driver by trade when he enlisted in the 301st (Mechanical Transport), 8th Company, Army Service Corps (17th Divisional Ammunition Park) on 19 November 1914 at the age of 25. His unit embarked from Melbourne, Victoria, on board HMAT A40 Ceramic on 22 December 1914 and by July 1915 he was in France attached to the Australian Army Service Corps as a driver. His period on service was marked by an ongoing illness and by a series of discipline issues. He returned to Australia on the Port Lyttleton and disembarked at Melbourne on Christmas Day 1918.

His brother, Pte Percy Clifford Smith, 31st Battalion, also served (Tree No. 1149)
Tree No. 1365