 Later he travelled to Tucumán where he joined José de San Martín y Manuel Belgrano, where he worked as the chief Secretary of the Army, working with San Martín to plan the campaign to liberate Chile and Peru.On May 20, 1816 Guido presented Antonio González Balcarce with "Memoria", which was based on his memories of conversations with San Martín in Saldán, Córdoba about the military, economic and political details of the Maitland Plan.After the victory at the Battle of Chacabuco (February 12, 1817).