Early in 1793, a British force was sent to Flanders to join an allied army against the French Republic. The 3rd Dragoon Guards took part in the decisive cavalry charge which led to an allied victory at the Battle of Beaumont in April 1794. All three regiments fought at the Battle of Willems in May 1794. During the battle, the 2nd (Royal North British) Dragoons broke into one of the French infantry squares which were formed to repel British cavalry attacks. This rare feat is thought to have been achieved by an unknown officer of the 2nd Dragoons who cut a gap in the square for his men to follow. With the other squares giving way, the rest of the British cavalry were able to rout the French army.
Owing to fears of a French invasion, the 3rd Dragoon Guards were stationed in Ireland from 1804. In 1809 they left for Portugal to join the campaign against Napoleon's armies in the Iberian Peninsula. Crossing into Spain, the regiment's first major engagement was at Talavera, before fighting at Albuhera in 1811 and besieging the cities of Ciudad Rodrigo and Badajoz in 1812. The 3rd Dragoon Guards saw action during the final battle of the Peninsular War at Vittoria in 1813, after which Napoleon's forces retreated into France.