In October 1884, when an expedition to relieve Khartoum was organised, Ardagh favoured an approach overland via Suakin and Berber, but the commander Lord Wolseley resolved to travel by boat up the Nile. Ardagh was appointed commandant at Cairo, with the grade of assistant adjutant-general. His energy, devotion, and quiet cheerfulness helped to expedite the fatal enterprise, and at the end of the disastrous campaign he was promoted to brevet colonel (25 August 1885), receiving the Order of the Medjidieh (3rd class). On 30 December, as chief staff officer of a combined British and Egyptian force, he took part in the battle of Ginnis, when a large army of the Khalifa, endeavouring to invade Egyptian territory, was defeated with great loss. For his services Ardagh was mentioned in despatches. On 17 December 1886 he was promoted to a regimental lieutenant-colonel, and on 26 January 1887 he was gazetted a colonel on the staff.