The Saltpeter War - 1879 - 1884

Since Chile became an independent Republic, it has claimed titles to the Atacama Desert area, which today corresponds to the Antofagasta region. Since 1822 the constitutional texts included, as the northern limit of the country, the Atacama Desert. However, Chile did not show interest in these lands, which were considered of little value, and at the time its greatest wealth was in the agricultural area of the center of the country.
The desert seemed to be an abandoned territory when Bolivian President Andrés de Santa Cruz decided to found the port of Cobija (1829) within the territory theoretically claimed by Chile, but whose government did not present any protest to the Bolivian Foreign Ministry. Chilean indifference would end when the economic value of the desert was discovered in the late 1839s. Important deposits of guano were found, a rich fertilizer in great demand by European countries and the United States.  That's when the border conflicts between the two countries began.  The Government of President Bulnes decided to send an exploratory commission to recognize the potential of the deposits in the area.
A law, dated 1842, declared the guaneras south of Mejillones Bay (23", south latitude) national property, which meant establishing the country's northern border on that line. The Government also began to grant permits to private entrepreneurs to load guano in the vicinity of Mejillones. In 1847, the Bolivian authorities decided to interrupt this activity and expelled Chilean businessmen and workers from the area.
The Chilean Government responded by sending troops to occupy Mejillones. Groups of Chilean workers, and soon after, big businessmen of the same nationality, were increasing their presence in the whole area, during the government of President Montt, which motivated repeated diplomatic claims by Bolivia, which claimed that the limit between both countries was on the 25th parallel" and not on the 23rd", as Chile claimed.