Viceroyalty of Peru arrived in Lima with Antonio José de Sucre to plan the offensive. In February 1824 the royalists briefly regained control of Lima. Olañeta's Rebellion started by surprise and the entire royalist army of Upper Peru (today's Bolivia) revolted, led by Pedro Antonio Olañeta (royalist) against La Serna, the viceroy of Peru (a liberal). This broke the royal army and started a civil war in Upper Peru. Having regrouped in Trujillo, Bolívar in June led his rebel forces south to confront the Spanish under Field Marshal José de Canterac. The two armies met on the plains of Junín on August 6,
First Upper Peru campaign richest cities of Upper Peru, an open cabildo calls Goyeneche to withdraw from their territory, which he obeys as he did not have military strength to prevail. The Bishop of La Paz, Remigio La Santa y Ortega, flees with him. Castelli is received in Potosí, where he required an oath of allegiance to the Junta and the surrender of the royalist generals Francisco de Paula Sanz and José de Córdoba y Rojas. He arranged that the operation to capture Vicente Nieto was carried out exclusively by the surviving patricians at the mines of Potosi, who had been incorporated with honors