The American War of Independence broke out in 1775; in 1778 France joined in the struggle and Great Britain was in danger of invasion. Seven thousand militia were camped on Warley Common which had increased to three regular and eight militia battalions by June. In October, George III and Queen Charlotte visited Lord Petre at Thorndon Hall to inspect the troops. The review included a mock battle in which 10,000 men were engaged. The following month the camp broke up, but was reformed in 1779, 1781 and 1782.
The French Revolution and Napoleonic wars saw the re-establishment in 1793 of the camp at Warley, and in about 1805 the barracks at Little Warley were built.
In 1793 the town was described as a populous place, with good inns, chiefly maintained by the multitude of passengers and carriers passing through to London. The White Hart (now known as Sugar Hut), so named after Richard II, who was said to have stayed there in the 15th century, is positioned in the middle of the High Street. It is one of the finest medieval inns in England and there is evidence to suggest that much activity took place on the site from around the 13th century, pre-dating the present structure.
The 16th century carriage entrance leads from the High Street to the inner courtyard which still exhibits a complete example of a wooden arched gallery. The fine workmanship of the inn is still apparent and suggests that it could have been built as a pilgrims' hostel, possibly sponsored by the monks of St Osyth.
Comparisons between the gallery of the White Hart and others in England show it to be the most complete and the most elegantly constructed of those that survive.
Before the advent of the railway, Brentwood's communications with the outside world depended mainly on the London-Colchester Road. Inns and hostels became regular stopping places for coaches. In 1791 there were three daily Brentwood to London coach services, and a wagon service four times a week.
Improvements to the main roads at the end of the 18th and the beginning of the 19th centuries brought about a considerable increase in traffic through Brentwood. The great Mr Macadam himself worked on the Shenfield to Chelmsford Road in 1833. To accommodate its growing trade, the White Hart's street front was extended eastwards during the 19th century, with a new north-east wing behind it, allowing 50 coach horses and 15 post horses to be stabled.