The 20th Light Dragoons participated in Admiral Popham and General Baird’s expedition to Buenos Aires from 1806 to 1807.

Admiral Popham and General Baird, supported by General Beresford, decided to mount an unauthorised expedition to Argentina, which was a Spanish possession. Having successfully taken Buenos Aires and plundered its treasury, the force found itself hard-pressed and called for reinforcements from Capetown.

The 20th had handed over their horses to the 21st Light Dragoons and therefore had to sail to the River Plate dismounted. Montevideo was taken, with the 20th acting well as light infantry, but subsequent operations in Buenos Aires were strongly resisted by the Spanish, forcing the expedition’s commander, General Whitelock, to sue for terms.