What caused the War of the Pacific between Peru and Chile?

The War of the Pacific (1879–1883) was primarily caused by a long-standing rivalry between Chile, Bolivia, and Peru over the control of valuable sodium nitrate deposits located in the Atacama Desert.12

While the conflict originated as a dispute between Chile and Bolivia regarding taxation and mining rights in the Atacama region, Peru’s involvement was driven by its traditional rivalry with Chile for hegemony on the Pacific coast. In 1873, Peru had entered into a secret mutual defense treaty with Bolivia.1

Tensions escalated in 1878 when Bolivia attempted to increase taxes on the Chilean-owned Antofagasta Nitrate Company, violating a previous agreement. When Bolivia threatened to confiscate the company's property, Chilean forces occupied the port of Antofagasta in February 1879. Bolivia subsequently declared war on Chile and invoked its alliance with Peru, leading Chile to declare war on both nations in April 1879. The war ultimately resulted in significant territorial losses for Peru and Bolivia, with Chile gaining control over the mineral-rich coastal regions.123