|Activity||Only son of Hugh, third earl of Loudoun, and Lady Margaret Dalrymple, only daughter of the first earl of Stair, was born on 5 May 1705. He succeeded his father in 1731, and from 1734 till his death was a representative peer of Scotland. |
He entered the army in 1727, was appointed governor of Stirling Castle in April 1741, and became aide-de-camp to the king in July 1743. On the outbreak of the rebellion in 1745 he raised a regiment of Highlanders (the 54th) on behalf of the government, of which he was colonel; and joining Sir John Cope, he acted with him as adjutant-general. After the battle of Preston, where almost the whole of his regiment was killed, he went north in the Saltash sloop of war, with arms, ammunition, and money, arriving at Inverness on 14 Oct. Within six weeks he had raised over two thousand men, and shortly afterwards relieved Fort Augustus, blockaded by the Frasers under the Master of Lovat. He then returned to Inverness, and marched to Castle Downie, the seat of Lord Lovat, whom he brought to Inverness as a hostage till the arms of the clan Fraser should be delivered up. Lord Lovat, however, made his escape during the night. In February 1746 Loudoun formed the design of surprising Prince Charles at Moy Castle, the seat of the Mackintoshes. The rebels, however, took possession of Inverness, and on their receiving large reinforcements Loudoun marched into Sutherlandshire, and, retreating to the sea-coast, embarked with eight hundred men for the Isle of Skye. From 1749, when his old regiment, the 54th, was disbanded, he held till 1770 the colonelcy of the 30th foot. From 1755 to 1757 he was also colonel-in-chief 60th foot (rifles).
On 17 Feb. 1756 Loudoun was appointed captain-general and governor-in-chief of the province of Virginia, and on 20 March commander-in-chief of the British forces in America. He arrived at New York on 23 July, and assumed command of the forces assembled in Albany. Affairs were in great confusion, and the home authorities were slow. The French had made themselves masters of Forts Oswego and Ontario. To conceal his plans for a siege of Louisburg, Loudoun, on 3 Jan. 1757, laid an embargo on all outward-bound ships, a measure which was reprobated both in America and England. Afterwards, when he had collected a force deemed amply sufficient, he wasted his time at Halifax, apparently unable to decide on a definite course of action, and was therefore recalled to England, General Amherst being named his successor. It was said of him by a Philadelphian that he ‘was like Saint George upon the signposts, always on horseback but never advancing.’ On the declaration of war with Spain in 1762, he was appointed second in command, under Lord Tyrawley, of the British troops sent to Portugal.
He was colonel 3rd foot guards 1770 till death, and governor of Stirling and of Edinburgh (1763 till death). He died at Loudoun Castle on 27 April 1782.
He was unmarried, and the title passed to his cousin, James Mure Campbell, only son of Sir James Campbell of Lawers (1667-1745), third and youngest son of the second earl of Loudoun. The fourth earl improved the grounds round Loudoun Castle, Ayrshire, and sent home a large number of trees from foreign countries. He more especially devoted his attention to willows.