 He was promoted to captain on 23 March 1900, and from November 1901 served as Aide-de-camp to Colonel Charles Egerton, Commander of the Punjab Frontier Force.He was mentioned in a despatch from Egerton dated 4 July 1902, following operations against the Mahsud Waziris.Munn served through the First World War, and was appointed a Companion of the Order of St Michael and St George (CMG) in the 1919 New Year Honours.