It was headed by Juan José Castelli, and attempted to expand the influence of the Buenos Aires May Revolution in Upper Peru (modern Bolivia).

[1] Before proceeding to Upper Peru, this military campaign defeated a counter revolution in Córdoba, organized by the former viceroy Santiago de Liniers.

As a result, the Junta appointed Juan José Castelli as commander of the Army of the North instead of Ocampo, and executed the prisoners on their way to Buenos Aires.

Balcarce, who had advanced to Potosi, was defeated by Nieto in the Battle of Cotagaita, so Castelli sent two hundred men and two cannons to strengthen his forces.

At Villa Imperial, one of the 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.

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 to the Army of the North.

He proclaimed the end of native slavery in the Upper Peru, canceling the tutelage and giving them political rights as neighbors, equal to those of the criollos.

He prohibited as well the establishment of new convents and parishes, to avoid the common practice that, under the guise of spreading the Christian doctrine, the natives were forced into servitude by religious orders.

[7] The first anniversary of the May Revolution was celebrated in Tiahuanaco with Indian chiefs, where Castelli paid tribute to the ancient Incas, encouraging people to rise against the Spanish.

In November 1810 he sent a plan to the Junta: to cross the Desaguadero river, border between the two viceroyalties, and take control of the Peruvian cities Puno, Cuzco and Arequipa.

Castelli argued that it was urgent to rise against Lima, because its economy depended largely on those districts and if they lose their power over the main royalist stronghold would be threatened.

Several saavedrist officers, such as José María Echaurri, José León Domínguez, Matías Balbastro, chaplain Manuel Antonio Azcurra and the sergeant major Toribio de Luzuriaga, planned to kidnap Castelli, deliver him to Buenos Aires for trial, and give the command of the Army of the North to Juan Jose Viamonte.

[11] When he knew about the fate of Moreno, Castelli wrote a mail to Vieytes, Rodriguez Peña, Larrea and Azcuénaga, asking them to move to the Upper Peru.

[5] However, the mail was sent by the common postal service, and the postmaster of Córdoba, Jose de Paz, decided to send it instead to Cornelio Saavedra.

The patriotic left wing, commanded by Diaz Velez, faced the bulk of the royalist forces, while the center was hit by the soldiers of Pio Tristan.