In 1957, McIntyre married Marion Jean Hillyard, an American he met while at Washington University, and they went on to have five children.

[1][2] In 1966, he was appointed a professor in history at the University of Canterbury, in Christchurch, New Zealand,[1] where he remained for the rest of his career.

An expert on the constitutional and military histories of the Commonwealth of Nations and British Empire, McIntyre published and advised governments.

He served as consultant to the Committee on Commonwealth Membership, and compiled its report which was accepted by Heads of Government at Kampala in 2007.

[6] In the 1992 Queen's Birthday Honours, McIntyre was appointed an Officer of the Order of the British Empire, for services to historical research.