After the First World War broke out in August 1914, Ackerley was commissioned as a second lieutenant in September 1914. He was assigned to the 8th Battalion of the East Surrey Regiment, part of the 18th Division, then stationed in East Anglia. In June 1915, he was sent to France. On 1 July 1916, he was wounded at the Battle of the Somme. He was shot in the arm and suffered shards of a whisky bottle becoming imbedded in his side from an explosion. After lying wounded in a shell-hole for six hours, he was rescued and sent home for sick-leave.