On the death of his uncle, he joined the British army in Portugal as a volunteer in the Peninsular War, at the age of sixteen. On 24 June 1811, at the age of nineteen, he received his first commission as 2nd Lieutenant in the 1st Battalion 95th Rifles (later the Rifle Brigade / Royal Green Jackets). Utilising his skills as a draughtsman of outstanding ability, he was occasionally employed in the Quartermaster-General's department under Sir George Murray. He was present at the storming of the fortresses of Ciudad Rodrigo, Badajos and San Sebastian as well as the battles of Salamanca and the Pyrenees. Subsequently, he would receive the Military General Service Medal with bars for each of these engagements.