Juan Manuel de Rosas rose to power in Argentina during a period of intense political polarization and civil war between Federalists and Unitarians in the early 19th century. As governor of Buenos Aires province from 1829-1835, Rosas consolidated power by controlling the army. He then declared himself dictator of Argentina in 1835, imposing a brutal conservative regime. Rosas' dictatorship lasted until 1852 when he was defeated at the Battle of Caseros by his former ally Justo Jose de Urquiza, ending 16 years of his authoritarian rule.