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.
General San Martín named Guido as Lieutenant Colonel, but he continued doing the job of Chief Secretary of the Army and Navy.
During the ceremony to mark the official declaration of Chilean independence on February 12, 1818, Guido played the role of flagbearer.
Guido was at the Guayaquil Conference where the two great Liberators of South America (San Martín and Simón Bolívar) met for the only time.
After San Martín left Peru, Guido stayed on, earning the titles of Supreme Military Advisor in 1823 and later Brigadier General.