The action of Juncalito was a military engagement of the Argentine War of Independence, previous to the Crossing of the Andes campaign.

On March 10, 1816, nine months before the crossing of the Andes, Jos Flix Aldao led a group of Mounted Grenadiers to the Uspallata Pass. They had to find out whether the pass was secure or the Spanish Royalists had fortified it. They found a scout Royalist group, and managed to capture them without firing a single shot. They captured a sergeant, a corporal and 15 soldiers.

With this information, San Martn spread the news that the bulk of the army would cross to Chile by Uspallata. This was in order to deceive the Royalists in Chile, as they kept fortifying that zone, but the bulk of the Army of the Andes actually moved near the city of Mendoza.

The Crossing of the Andes (Spanish: Cruce de los 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 royalist-held 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 21 days.