He supported the patriot side on the Chilean War of Independence from the beginning, and in 1811 he was dispatched by the First Government Junta to support the government of Buenos Aires, then under threat from a Royalist invasion. He took with him a small contingent, named the "disciplined troops" (), composed of 200 infantry soldiers and 100 "Dragones de la Frontera" cavalry. Among the 27 officers he took along were the captains José Joaquín Prieto, future President and Manuel José Bulnes, father of the president of the same name. They arrived to Buenos Aires on June 16, where they supported José de San Martín and the creation of the Second Triumvirate during the revolution of October 8.