Doyle was born in 1758 in Dublin, the fifth son of Charles and Elizabeth Doyle of Bramblestown, County Kilkenny, and a younger brother of John Doyle.
Doyle joined the army in 1770 as an ensign in the 55th Regiment of Foot, and was promoted lieutenant in September 1773. He served in North America with his brother from 1775, seeing action in the American War of Independence and was elevated to captain of the 55th in November 1777. Under Rawdon he served at the Battle of Camden, 25 April 1781, after leading a small force to raid Snow Island in March. He sailed back to Great Britain with his brother and Rawdon later that year, but was captured en route by the French fleet, to be later exchanged.
Doyle was appointed lieutenant-colonel of the 105th Foot (former "Volunteers of Ireland") in March 1782, but placed on half-pay after the peace. He was Military Envoy to Poland and Warsaw during the 1780s. Doyle was made lieutenant-colonel of the 14th Regiment of Foot in March 1789, and commanded the regiment in the Flanders Campaign under the Duke of York in 1793. He distinguished himself at the Battle of Famars 22 May by leading an attack on an entrenched camp. After an initial rebuff from a French force that could be heard playing the patriotic march "Ça Ira" to urge on its men, Doyle ordered his own men to strike up the same tune, saying "We'll beat them to their own damned tune". The position was taken and the 14th were ordered by York to henceforth use "Ça Ira" as their marching tune in honour of the occasion. Doyle was appointed brigadier-general in November 1794, and promoted major-general in February 1795.
After the evacuation from Holland he joined the Royalist survivors of the invasion of France at the Île d'Yeu with 4 British foot regiments and 3 Royalist cavalry units from September, commanding the total 5,000 men. He commanded the attack on Hedic and Houat in August. Eventually this force was obliged to withdraw due to serious supply problems after the failure of the War in the Vendée to raise support.
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