As Earl of March, he served on Wellington's staff in the Peninsular War, during which time he volunteered to join the 52nd (Oxfordshire) Regiment of Foot's advance storming party on the fortress of Ciudad Rodrigo. He formally joined the 52nd Foot in 1813 and took command of a company of soldiers at the Battle of Orthez in 1814, where he was severely wounded; the musket-ball in his chest was never removed. During the Battle of Waterloo (1815) he was aide-de-camp to the Prince of Orange, and following the latter's wounding, served as aide-de-camp to Wellington. He was chiefly responsible for the institution in 1847 of the Military General Service Medal for all survivors of the campaigns between 1793 and 1814, considered by many belated as hitherto there had only been a Waterloo Medal. He campaigned in Parliament and also enlisted the interest of Queen Victoria. Richmond himself received the medal with eight clasps.