He was of short stature for a Highlander--about five feet eight--lean and dark, with straight black hair.

He had a serious unhandsome countenance which, at casual glance, might not arrest attention; but when he spoke he became magnetic, by reason of the intelligence and innate force that gleamed in his eyes and the convincing sincerity of his manner.

He was admired and respected by his brother officers and by the commanders under whom he had served, and he was loved by his men.
He had seen his first service in the Seven Years' War, having joined the British army in Flanders at the age of fifteen; and he had early distinguished himself for courage and coolness.

In 1768, as a captain of infantry, he quelled an insurrection of the natives on the island of St.Vincent in the West Indies.

Later, at Woolwich, he took up the scientific study of his profession of arms.