The aggressions of France in America were followed by a declaration of war; when the King of France made preparations for a descent upon England, which produced considerable alarm in the kingdom; but the designs of the enemy were frustrated by the warlike preparations of the British Government. In this year (1756) the establishment of the THIRD DRAGOON GUARDS was 24 officers, 7 quarter-masters, and 427 non-commissioned officers and private men.
During the summer a detachment of the regiment was stationed at Kensington to assist the Life Guards in the performance of the travelling escort-duty for the royal family.
In July, 1757, the regiment was encamped, with several other corps, on Salisbury Plain, under the command of Lieut.-General Hawley; and a brigade was there formed of the LIGHT TROOPS of several regiments, for instruction in the evolutions, and in services peculiar to light cavalry. In autumn the regiment marched to quarters at Colchester, Malden, and Witham.
The augmentation made in the naval and military establishments of the kingdom enabled the British Government to act offensively, and in the spring of 1758 the LIGHT TROOP of the THIRD DRAGOON GUARDS was called upon to hold itself in readiness for actual warfare. In April it was ordered to encamp near Petersfield, where a brigade was formed of the light troops of nine regiments, under the command of Colonel Eliott, of the Horse Grenadier Guards. Towards the end of May the brigade embarked on board transports,--forming part of an expedition under Charles Duke of Marlborough, designed for a descent on the coast of France. On the 5th of June the Fleet arrived in Cancalle Bay, on the coast of Brittany, and, having silenced a battery on the shore, part of the troops were immediately landed; when a battalion of French infantry and two troops of cavalry, posted on the heights near that place, retired without making opposition. On the following day the brigade of light cavalry and the artillery were landed; and on the 7th the whole (excepting three battalions of infantry left to cover the coast) marched to the vicinity of _St. Maloes_, and during the night the light cavalry, with detachments from the infantry, set fire to the shipping and naval stores at St. Servan, destroyed a fleet of privateers, with a man-of-war of fifty guns, and another of thirty-six, and afterwards retired. The capture of St. Maloes had been designed; but the expedition was not provided with troops and heavy ordnance sufficient for so great an undertaking; consequently that design was laid aside, and on the 11th of June the light cavalry were re-embarked. A second descent being rendered impracticable by severe weather, the fleet returned to England, and the light cavalry landed and encamped near Portsmouth and subsequently on Southsea Common.