After failing to capture the Spanish fortress of Real Felipe in El Callao, Cochrane decided to assault the city of Valdivia, the most fortified place in South America at the time. Valdivia was considered a threat to Chilean independence as it was a stronghold and supply base for Spanish troops. Valdivia provided a safe landing site for sending reinforcements to the loyalist guerrilla fighting the Guerra a muerte in the area of La Frontera.