With the outbreak of war, he was appointed the commandant of the Karrakatta training camp in 1914. Commissioned into the First Australian Imperial Force in March 1915 as brigade major of the 5th Brigade, serving with the brigade for the majority of the Gallipoli campaign. He was awarded the Distinguished Service Order for his services at Gallipoli. Given command of the 18th Battalion in February 1916 and arriving in France in March 1916. He led the battalion during the Battle of Pozières Heights and the Battles of the Somme. He was promoted to colonel and temporary brigadier general and appointed to command the 7th Brigade and led the brigade at the Battle of Lagnicourt in March 1917 and the Second Battle of Bullecourt in May. Wisdom was appointed the Companion of the Order of the Bath in June. He went on to command the brigade at battles which captured the Menin Road, Broodseinde and Passchendaele.