José de San Martín Manuel Rodríguez had returned to Chile before the crossing, and began a guerrilla war in Santiago de Chile against the royalists, in support of the upcoming army. He was supported in the south of the city and the countryside. The strategy was to occupy nearby villages, seize the royalists' weapons and flee. The attacks on Melipilla and San Fernando, and a failed one at Curicó, demoralized the royalists. The columns that crossed the Andes began to take military actions. The column in the north led by Cabot defeated the royalists in Salala, seized Coquimbo and then Copiapó. In the south,
José de San Martín that it was not possible to defend Concepción, so he ordered O'Higgins to leave the city. 50,000 Chileans took cattle and grain and moved north, burning everything else, so that they did not leave supplies for the royalists. As he had done with the Tucumán Congress, San Martín urged a declaration of independence, to legitimize the government and the military actions. The Chilean Declaration of Independence was issued on 18 February 1818, one year after the battle of Chacabuco. San Martín, Las Heras and Balcarce met in Curicó, and the royalists in Talca, in a plain known as "Cancha rayada".