In July 1916, the 25th Battalion took part in its first major Western Front action at the Battle of Pozières, part of the Somme offensive. The battalion suffered 785 casualties between 25 July and 7 August. It was briefly transferred to a "quieter sector of the front in Belgium" before returning to action on the Somme in October. On 3 November, Towner was transferred to the Australian Machine Gun Corps and was assigned to the 2nd Machine Gun Battalion of the 2nd Australian Division, and was allotted to the 7th Brigade's Machine Gun Company. He was commissioned as a second lieutenant fifteen days later, and assumed command of the battalion's transport section.