Crossing of the Andes The Crossing of the Andes was one of the most important feats in the Argentine and Chilean wars of independence , in which a combined army of Argentine soldiers and Chilean exiles invaded Chile leading to Chile ' s liberation from Spanish rule . The crossing of the Andes was a major step in the strategy devised by José de San Martín to defeat the royalist forces at their stronghold of Lima , Viceroyalty of Perú , and secure the Spanish American independence movements . Setting out from Mendoza ( then part of the Province of Cuyo ) in January 1817 , their goal was to enter Chile without being noticed , through unexpected paths , so as to attack the royalist forces by surprise . The ultimate objective was the liberation of Chile from Spanish rule with Argentine forces . Led by José de San Martín , the crossing took twenty - one days . Antecedents . The idea of crossing the Andes was already developed by lodges seeking the independence of South America , and was part of the Maitland Plan designed by Thomas Maitland . San Martín learned of it during his brief time in Britain , before sailing to South America . After becoming aware of the difficulty of attacking the royalist stronghold of Lima across the Upper Peru , he decided to proceed with such plan . The Captaincy General of Chile had removed their governor in 1810 , and replaced him with the First Government Junta , starting a period of Chilean history known as Patria Vieja . However , they would be defeated in 1814 during the battle of Rancagua , and with the Reconquista Chile would become again a royalist stronghold . Bernardo O ' Higgins and other Chilean leaders had fled to Mendoza during the new royalist government , which led to O ' Higgins being part of the Army of the Andes as well as the Argentine soldiers . Troops and Equipment . The city of Mendoza , during this time frame , became a factoring headquarters during the pre - crossing . The citizens of Mendoza assisted their troops by manufacturing gunpowder and ammunition . They also learned to make cannons . The main food of the army was a regional meal called " valdiviano " . It was prepared with dry meat or " charqui " , sliced raw onion , and boiling water . They had designated soldiers who carried the food . These soldiers transported forty tons of charqui ; maize cakes ; meat ; brandy , to counter the nighttime cold ; garlic and onion , to deal with the lack of appetite ; more than 4 , 000 cattle for the rest of the campaign ; plus cheese and rum . The Crossing . On the morning of January 19 , 1817 , San Martin and his army set out from their base camp " El Plumerillo " and began their journey across the Andes Mountain range . San Martin crossed with 4 , 000 men , only to end up losing 1 / 3 of them . It was a devastating blow to the troop . The number of auxiliaries reached 1 , 200 . For the crossing , San Martin split his army into two divisions : The main division , which traveled through the pass of Los Patos , was led by San Martin , Miguel Estanislao , and Bernardo O ’ Higgins . The secondary troop , which traveled through the more southern Uspallata , was led by Juan Gregorio de Las Heras . Coming to an End . On February 13 , 1817 , San Martín , O ’ Higgins , and their army successfully entered Santiago , Chile , after crossing 500 kilometers of mountain range , and the journey came to an end . The royalist forces , by this time , had advanced north to avoid San Martín ' s army , but a royalist leader had stayed behind with 1 , 500 men to advance at a valley called Chacabuco , which was located near Santiago . Thus , the Battle of Chacabuco began . 2010 . On 2010 the Argentine and Chilean armies recreated the crossing during the conmemorations of the 200 years of Independence