Juan Manuel de Rosas (1793-1877), Argentine dictator of the 1830s and '40s. Born in Buenos Aires, Rosas belonged to a family prominent there under Spanish rule. He amassed great wealth as a cattleman and beef exporter during the period when Argentina was establishing its independence. In 1827 he emerged as a military leader and champion of the country's conservative aristocracy, which favored provincial autonomy, and opposed foreign influence and the liberal reforms advocated by the centralist Unitario faction. From 1829 to 1832 he was governor of Buenos Aires Province. In 1833 he led a successful campaign against the Native Americans of southern Argentina and two years later was reinstated as governor with dictatorial powers. Supported by the Mazorca, an organization that terrorized his Unitario opponents, Rosas formed alliances with the strongmen who dominated the other Argentine provinces, winning for himself control of the nation's foreign affairs and external trade. In 1843 he intervened in a civil war in neighboring Uruguay, arousing fears of Argentine expansionism. Britain and France retaliated by blockading Buenos Aires, but Rosas persevered. In 1851 Justo Urquiza, a former supporter of Rosas, led a rebellion against him backed by Brazil and Uruguay. Ousted in 1852, Rosas spent the rest of his life in exile and died in England.