The Chilean occupation of Peru (Spanish: Ocupación chilena del Perú) began on November 2, 1879, with the beginning of the Tarapacá campaign during the War of the Pacific.

However, Chilean forces continued to occupy and administer Tarata until 1925, while a final agreement between the two countries regarding Tacna and Arica was reached in 1929.

A maritime bombing and subsequent landing at Pisagua proved successful for the Chilean troops, who quickly occupied the town and set it as their base from which to continue the invasion up north.

Peruvian General Juan Buendía, who was in command of the Allied Southern Army at Tarapacá, was left in a difficult position.

The Allies left Tarapacá, withdrawing north-west to Arica on the coast, moving through the area close to the mountains to avoid the Chilean cavalry attack.

By early 1881, fighting had reached the outskirts of the capital, and after the Chilean success at Chorrillos and Miraflores, the occupation of Lima began in January 1881, with Chilean troops occupying the capital and establishing a military administration headquartered in the Government Palace, while the collaborationist government was headquartered in the Palacio de la Magdalena.

Reports of Chilean destruction and looting resulted in a meeting between the different observing powers, concluding that such an event would not be allowed in Lima proper.

[5][6] Despite a relatively peaceful administration in comparison to the destruction in Barranco, Chorrillos and Miraflores, the city of Lima was looted by Chilean forces, such as in the case of the National Library of Peru.

After the occupation, Chile diverted part of its war efforts to crush Mapuche resistance in the south, with some of its equipment captured from Peruvian troops, as well as civilians.

The movement itself was mainly headed by Nicolás de Piérola, who established three armies to counter the Chilean invasion in the north, center and south of the country.

[15] Montero initially established his government in Cajamarca, later moving to Huaraz in June 1882, and leaving for Arequipa, refusing to accept the Chilean terms for a peace treaty.

In late 1883, amid civil discontent at the news of the imminent occupation by Chilean troops, Montero left Arequipa for Puno to avoid its destruction, with the city being occupied shortly after.

[17][18] By the time he reached Lake Titicaca, he put Cáceres in charge of the powerless government, who did not exercise power in the end, later recognizing the Treaty of Ancón.

[19] Iglesias assumed command of the northern departments per Montero's instructions, and established a "Free North Government"[24] in Trujillo in July 1882.