Battle of Rancagua Battle of Rancagua The Battle of Rancagua also known as the Disaster of Rancagua occurred on October 1, 1814, to October 2, 1814, when the Spanish Army under the command of Mariano Osorio defeated the rebel Chilean forces led by Bernardo O’Higgins. This put an end to the Chilean Patria Vieja and it was the beginning of the Spanish Reconquista of South America. When Spain heard about the Patriot revolt in Chile, they sent an army of Spanish soldiers and royalists to defeat the rebellion. When O'Higgins heard about the besieged army in Rancagua, he went with his army of
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".