The principal Spanish colonies in South America were, as has been seen, on the western side of the continent. Balbao crossed the isthmus of Panama in 1513. In 1531 Pizarro landed in Peru, where he encountered and overthrew the empire of the Incas. Valdivia, one of his ablest lieutenants, made his way still further south, and in 1541 founded Santiago, the present capital of Chile, on the fruitful plain between the Andes and the sea. His further progress was checked by the Araucanians, a warlike tribe of Indians, who offered a much stronger resistance than the Incas. They were never entirely conquered, and the Spaniards in Chile were engaged in perpetual struggle with them, while at the same time open to attacks on the coast from European powers who were at enmity with Spain. When the revolutionary waves swept the continent the Chilean patriots were at first compelled to withdraw across the Andes. The most famous of them was Bernardo O’Higgins; his father, originally a barefooted Irish boy, was one of the last viceroys of Peru, and the son became one of the first presidents of the new republic. Argentina had at this time accomplished her own freedom, and was able to send help to Chile. General San Martin crossed the Andes, and inflicted a crushing defeat on the Spaniards at Maipu in 1818. The revolutionary army then passed north, the Viceroy evacuated Lima, and at Guayaquil San Martin met the liberator Bolivar, who had marched down from the north. Meanwhile Admiral Cochrane, who had reorganised the Chilean and Peruvian navies, had been engaged in freeing the Pacific from Spanish ships. South America thus was finally cleared from the domination of the Spaniard. Disputes, however, arose between the new republics as to their respective boundaries: Chile fought Peru in 1879 over the possession of the nitrate-fields, and issued victorious from the struggle. The long series of difficulties between Chile and Argentina was ended, as has been recorded, through British arbitration, in 1902.