The great bravery of the 42nd Highlanders and the admirable service which they rendered at the Battle of Fontenoy, made the Government anxious to avail themselves still further of the military qualities of the Highlanders. Authority, therefore, was given to the 4th Earl of Loudoun to raise another Highland regiment under the patronage of the noblemen, chiefs, and gentlemen of that part of the kingdom, whose sons and connections would be appointed officers.
Lord Loudoun had an easy task, as recruits rapidly joined the colours. Soon a body of 750 men assembled at Inverness and the remainder at Perth. The regiment consisted of twelve companies under John, Earl of Loudoun, as Colonel, and John Campbell (afterwards Duke of Argyll), Lieutenant-Colonel. The officers commissions were dated the 6th of June 1745.
Before the regiment was disciplined the Rising of the '45 commenced. So rapid were the movements of Prince Charlie's forces that communication between the two parts of the regiment (at Inverness and Perth) was cut off. Eight companies under Lord Loudoun, were occupied in the northern Highlands while the remaining four companies served in the central and southern Highlands.
The force under Lord Loudoun were the victims of the ignominious Rout of Moy, when during the darkness of the night they were put to flight by a handful of the Clan Chattan and the bold tactics of Lady Mackintosh. At the Battle of Prestonpans every officer and man of the three companies was taken prisoner by the Jacobites.
In 1747 Loudoun's Highlanders embarked for Flanders, where they served until the peace of 1748, when they returned to Scotland and were disbanded at Perth.