He joined the 18th Battalion of the First AIF early in 1915, shortly after the outbreak of World War I and was wounded at Hill 60. He had been contributing cartoons and sketches to "The Bulletin" before enlisting, and continued after 1916 when was invalided to London. As much as anyone, he was responsible for the portrayal of the Australian "digger" as independent, easygoing and disrespectful of authority. During his convalescence, he contributed to "The London Bystander", "Passing Show" and "London Opinion", then worked as a staff sergeant leading a camouflage team.