Peru and Chile sign the Treaty of Ancón

Background. Following the occupation of Lima in January 1881, political instability in Peru led to the rise of Miguel Iglesias's government in 1883. Recognized by Chile, this administration established negotiations that culminated in the Treaty of Ancón. The agreement marked the formal end of hostilities between Chile and Peru, concluding Peru's involvement in the broader conflict.

Treaty Terms. The treaty required Peru to formally cede Tarapacá province to Chile. It also regulated the use of guano and nitrate resources to repay Peru's debts. While Tacna and Arica were subject to a ten-year provisional administration by Chile, the immediate effect was the cessation of war and the transfer of Tarapacá, which existed as a Chilean territory from 1884 to 1976.

Immediate Aftermath. The signing of the treaty triggered internal conflict in Peru, leading to the Peruvian Civil War of 1884–1885 which overthrew Iglesias' government. Despite the treaty, resistance continued briefly; Cáceres accepted the treaty as an accomplished fact in June 1884 but continued fighting. The Chilean occupation of Lima ended in October 1883.