Arthur Wellesley, Marquess Wellington drove the French from northern Spain by his decisive victory at the Battle of Vitoria on 21 June 1813. When the French Army of the North withdrew over the Pyrenees, its commander General of Division Bertrand Clausel left a garrison of about 3,000 men and 80 pieces of heavy artillery in the fortified city of Pamplona. This force, under the leadership of Louis Pierre Jean Aphrodise Cassan, was later increased somewhat by numbers of straggling and sick soldiers. A Spanish army under Enrique José O'Donnell invested the city. In the Vitoria campaign in June, O'Donnell's 14,183-strong Army of the Reserve of Andalusia consisted of two divisions of infantry under Generals Creagh and Echevarri and a brigade of cavalry led by General Barcena. Creagh had 6,454 me