[5] In 1755, Macbean was selected to command an artillery detachment in Ireland, but with the adjutancy at Woolwich falling vacant at the same time, he purchased its commission (and the attendant rank of first lieutenant) under the system then in force.

At the battle of Minden in August 1759, where his brigade consisted of ten medium 12-pounders manned by two companies, he rendered conspicuous services, for which he received an autograph letter of thanks from Field Marshal Prince Ferdinand of Brunswick and a gratuity of 500 crowns.

On his return home on sick leave soon after, he was recommended to the king by Prince Ferdinand for some special mark of royal favour, which he never received.

In 1762 he embarked with his company for service in the Portuguese Campaign under the Count of Lippe, of which he left a manuscript account placed in the Royal Artillery Institution, Woolwich.

The artillery service was greatly indebted to him for his private notes and memoranda, without which much valuable information relating to the earlier history of the corps would have been lost.