Pakenham was an Anglo-Irish career officer in the British Army. Commissioned as a Lieutenant in the 92nd Regiment of Foot he first saw action during the Irish Rebellion of 1798 and in the Caribbean. During the Peninsular War, he served as Adjutant-General to his brother-in-law Arthur Wellesley, who would later become the Duke of Wellington. He commanded units at the Battle of Bussaco and Fuentes de Oñoro, and a Division at Salamanca. For his actions, he was inducted into the Order of the Bath. After being promoted to Major General, he replaced General Robert Ross, who was killed prior to the Battle of North Point, as commander of the British North American Army in 1814. Pakenham was in command at the Battle of New Orleans, where he was mortally wounded at the age of 36.