Harding attended Blundell's School in Tiverton (1801–7), about 28 miles south-east of his home at Upcott, during which time his father died. In July 1811, aged 18, his military career commenced when he received a commission as ensign and served with the 5th Regiment of Foot (later renamed 5th Northumberland Fusiliers) during the Peninsular War, during which he was present at the Siege of Burgos (1812), the capture of Madrid (1812), and fought in the Battle of Vitoria (1813), Battle of the Pyrenees (July 1813), and the battles of Nivelle, Nive, Orthes and Toulouse, having been promoted Lieutenant in 1813. He was awarded the Military General Service Medal with six clasps.