Gran Colombia–Peru War was the kernel of Bolívar's grander scheme to unite the former Spanish colonies in Central and South America. Prior to becoming the titular head of Gran Colombia, Bolívar had been, briefly, the president of the newly independent state of Bolivia, his namesake. Bolivia had formerly been a part of the Viceroyalty of the "Rio de La Plata", known as Upper Peru, and, once Bolívar relinquished the presidency of Bolivia to his revolutionary compatriot, Antonio José de Sucre Alcalá, in 1826, the Peruvians saw an opportunity. Early in 1828, Peru launched a campaign against Bolivia to reclaim its former territory and
First Upper Peru campaign authorities. The May Revolution, in Buenos Aires, was more successful, and ousted the viceroy Baltasar Hidalgo de Cisneros. The Primera Junta, which replaced him, prepared a military expedition to Upper Peru to secure the control of the area, while another expedition headed to Paraguay. Before proceeding to Upper Peru, this military campaign defeated a counter revolution in Córdoba, organized by the former viceroy Santiago de Liniers. Ortiz de Ocampo disobeyed orders to execute the prisoners, sending them to Buenos Aires instead. As a result, the Junta appointed Juan José Castelli as commander of the Army of the North instead of