He moved to the United Provinces of the Río de la Plata (modern Argentina), and joined the Army of the North, under the command of Manuel Belgrano. He fought in the battles of Tucumán and Salta, being injured in both. He was sanctioned by Belgrano for promoting a duel. As a result, he did not take part in the battles of Vilcapugio and Ayohuma, two defeats of the Army of the North, and Belgrano regretted later the absence of Dorrego from them.