He served in Denmark, and was present at the engagement of Koege (Køge), and, his regiment being shortly afterwards sent to Spain, he bore himself nobly through the retreat to Corunna, the hardships of which permanently impaired his health. In 1809 he became "aide-de-camp" to his cousin the Duke of Richmond, Lord Lieutenant of Ireland, but joined the 43rd when that regiment was ordered again to Spain. With the light brigade (the 43rd, 52nd, and 95th), under the command of General Craufurd, he marched to Talavera in the famous forced march which he has described in his "History", and had a violent attack of pleurisy on the way.