From 1977 to 1982 he held the appointment of Chief of the General Staff, before retiring from the Army having overseen a large-scale re-organisation.

[3] With the 27th Battalion, Dunstan saw combat against the Japanese during the Bougainville Campaign in 1945, and received a Mention in Despatches for his actions while commanding a platoon.

Having reached the rank of colonel, in early 1968 he was deployed to Vietnam as deputy commander of the 1st Australian Task Force (1 ATF).

[10][11] That year he returned to Australia and on promotion to brigadier took over the 10th Task Force, which was based in New South Wales.

He attended the Imperial Defence College in London in 1970 and afterwards he was promoted to major general and appointed Commander of Australian Forces in Vietnam.

[13] His next appointments were Chief of Materiel in Army Headquarters (1972–74) and General Officer Commanding Field Forces (1974–77).