private, he embarked aboard HMAT Aeneas from Brisbane on 29 June, bound for Egypt. The troopship arrived in August, and the battalion spent the rest of the month training in the desert before transferring to the Gallipoli Peninsula. Towner, however, remained in Egypt with the army's transportation elements. Following the Allied evacuation of Gallipoli, the 25th Battalion returned to Egypt in December 1915, where Towner rejoined its ranks on 10 January 1916. He was promoted to sergeant on 1 February, before departing with the battalion at Alexandria the following month to join the British Expeditionary Force on the Western Front. Disembarking at Marseilles, the unit was the first Australian battalion to arrive in France. 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. Promoted to lieutenant on 24 February 1917, Towner's service with his transport section earned him praise for his "devotion to duty and consistent good work", and on 9 April he was Mentioned in the Despatches of Field Marshal Sir Douglas Haig. Towner was granted leave to the United Kingdom in January 1918. He received a second Mention in Despatches on 7 April 1918, the notification of which was published in a supplement to the London Gazette on 28 May. On the night of 10/11 June 1918, Towner was in command of a machine gun section during an attack to the south of Morlancourt. One of the first to reach the objective, he deployed his section and got its guns into action "very quickly". By using captured German machine guns he was able to increase his section's fire and provide support to the company on his right as it advanced, seized, and consolidated its position. During the morning of 11 June, one of the posts held by the Australian infantry was blown in by German