After defeating the Peruvian army at Chorrillos and Miraflores and entering into Lima on early 1881, the Chileans are busy trying to restore order in the Peruvian capital city, at that time under the command of Gen. Pedro Lagos. Since signing a treaty ceding territory was rejected, Chile is obliged to eliminate all resistance in order to force peace under its terms. Therefore, an expedition directed by Lt. Col. Ambrosio Letelier is sent to the mountains in order to destroy the resistance organized by Gen. Andrés Cáceres.