[1] Entering the Royal Military College, Duntroon, he graduated as a lieutenant in 1939, and was posted to the 2/15th Battalion the following year for active service during the Second World War.

MacDonald remained with the unit until the end of the war,[1][3] which included seeing action at El Alamein during the North African Campaign, and New Guinea in the South West Pacific theatre.

[4] In the 1953 New Year Honours, MacDonald was appointed an Officer of the Order of the British Empire for his service with the Australian Staff Corps.

[3] On 26 January 1968, MacDonald arrived in Vietnam and assumed command of the army component of the Australian forces in the country.

[14] He is remembered as one who "possessed a fierce temper and an often irascible nature, which, combined with considerable intelligence and a capacity for hard work, made him a sometimes difficult superior.