He served with the regiment against the jacobite rebels of 1745, and was with that part of it which captured the troops landed in Tongue Bay from the sloop Hazard on 25 March 1746. These troops, belonging to the French service, but mainly Irish in nationality, numbered about 170, while their captors were only half that strength. The credit of this achievement was claimed by
Lord Reay and his sons, one of whom was a captain in Loudoun's regiment: but, in a memorial to
Lord Amherst, Reid affirmed many years afterwards, and brought some evidence to show, that it was really due to him. When his superior officers, considering the enemy too strong, had retired, he had persuaded some of the men to remain with him; and at the risk of a
court-martial he had persisted in the attacks which at length forced the enemy to surrender. About £12,000 of money was taken, and the loss of this at a time when the Jacobite army was otherwise destitute was, according to Francis Farquharson, who commanded a regiment in that army, 'the chief cause of taking that desperate resolution of engaging the king's army at
Culloden'.
Reid served with his regiment in
Flanders in 1747-8, and took part in the defence of
Bergen op Zoom. When peace was made in 1748 the regiment was reduced, and Reid bought a commission as captain-lieutenant in the 42nd highlanders on 26 June 1751. He became captain 3 June 1752, and major 1 August 1759. He served in the expedition against Martinique under Colonel (afterwards General)
Robert Monckton in January 1762, and in command of the 1st battalion of the 42nd he took a prominent part in the attack on the French positions on the Morne Tartaneon (24 January), and was himself wounded in two places. On 3 February he was made brevet lieutenant-colonel.
In the same year he was at the siege of the Havannah, which lasted two months, and cost his battalion heavy losses from sickness. In October the 42nd went to
British North America, having been reduced to one battalion, and in 1764 Reid was second in command in
Bouquet's expedition against the western and Ohio Indians, which followed on
Pontiac's Rebellion. In 1770, after nearly twenty years in the 42nd, he was placed on half-pay. On 29 Aug. 1777 he was promoted colonel, and on 19 October 1781 major-general. When some new regiments were added to the establishment on account of French intervention in the war between Great Britain and the American colonies, he raised one, the 95th of which he was colonel from 7 April 1780 till 31 May 1783, when it was disbanded. Reid became lieutenant-general 12 October 1793, and on 27 November 1794 he was made colonel of the 88th foot (Connaught Rangers).
In the previous July he had written to Lord Amherst, the commander-in-chief under whom he had served in America asking for the colonelcy of a regiment not liable to be reduced after the war, and setting forth in detail, perhaps with some exaggeration, his past services and the losses he had sustained. He had acquired, chiefly by purchase, about thirty-five thousand acres of land in
Vermont, and had erected mills and made other improvements. But the land had been forcibly seized by settlers from
New England in 1774, and the outbreak of the war had deprived him of a remedy.
He became general 1 January 1798, and died in the Haymarket, London, 6 February 1807.