Wellesley returned to Portugal in April 1809 to command the British army, reinforced with Portuguese regiments trained by General Beresford. After taking command of the British troops in Portugal on 22 April, Wellesley immediately advanced on Porto and made a surprise crossing of the Douro River, approaching Porto where its defences were weak. Soult's late attempts to muster a defence were in vain. The French quickly abandoned the city in a disorderly retreat.

Soult soon found his retreat route to the east blocked and was forced to destroy his guns and burn his baggage train. Wellesley pursued the French army, but Soult's army escaped annihilation by fleeing through the mountains. The other northern cities were recaptured by General Silveira. The battle ended the second French invasion of Portugal.