Conflicting Argentine and Chilean claims to Patagonia, the southernmost region in South America, had been causing tension between the two countries since the 1840s. Both countries were incapable of enforcing these claims with a seaborne force, though: in 1860, the Chileans had only five small vessels, while the Argentine Navy had no seagoing ships. These attitudes quickly changed when the circumstances warranted; when Chile joined Peru against Spain in the Chincha Islands War, the Spaniards blockaded and bombarded Valparaíso, leading the Chilean government to strengthen the navy. The Argentine government, under President Domingo Sarmiento, decided to build a navy in the 1870s to counter Brazilian naval acquisitions. Two large monitors, "Los Andes" and "El Plata", were ordered from Laird Brothers, a British company, along with two gunboats. They were delivered in 1874 and 1875.