Following the outbreak of the First World War Potts requested to the join the Australian Imperial Force (AIF), a volunteer force that was being formed for active service overseas. On 26 January 1915 he was called up and he was quickly promoted to acting sergeant while still only 18, due both to his prior service and his obvious leadership qualities. He soon earned the respect of his men, most of whom were much older than he. Potts was posted as a reinforcement to 16th Battalion at Gallipoli in July, just in time to participate in the bloody battles of 7 and 8 August.