 He was granted brevet rank as a colonel on 1 March 1711.On 27 June 1737, after nearly forty-eight years' service in various parts of Europe, Irwin was appointed colonel of the 5th Regiment of Foot, and following promotion to brigadier-general on 1 January 1743 and major-general on 24 February 1744, he held important commands on the staff in Ireland, where he was also Lieutenant-Governor of Kinsale.He was promoted to lieutenant-general in 1748.