He served with the grenadiers in Sicily (1806), at Coruna (1808), on Walcheren (1809), and in Spain and France from 1812 to 1814. In 1815, Lord Saltoun fought as a captain in the First Regiment of Guards (later the Grenadier Guards) in the Orchard at Hougomont on the morning of the Battle of Waterloo. During the battle he had four horses shot from underneath him.