January 19, 1817

Crossing of the Andes

Two Army of the Andes formations depart on separate routes

The 5,423-man army did not march out in a single column, and San Martín was not at its head — he stayed behind until the 24th, then set off to catch his own leading divisions.

What the operations diary records for 19 January

The army's operations diary records that on 19 January 1817 a train of 4-pounder field artillery left El Plumerillo, following Colonel Juan Gregorio de Las Heras's rear toward Uspallata.

The same diary records a vanguard division under Antonio Melián — the 4th squadron of mounted grenadiers with four companies of grenadiers and voltigeurs — departing toward the Los Patos route.

Both were components of a staggered, multi-column operation already in motion.

Not one army, and not one morning

San Martín's letter of 24 January states that the army had begun leaving on 18 January, completed its departure on the 24th, and that he himself would leave that afternoon to catch the leading divisions.

Men, artillery, livestock and supplies moved in timed stages along different Andean passes, both to manage the logistics and to confuse the royalist command about where the main attack would come.

The figure of 5,423 men — with 9,280 mules, 1,500 horses and 16 pieces of artillery in a later Argentine military-history synthesis — describes the whole army, not the troops documented as leaving on the 19th.

A date pinned to the wrong continent

Summaries date the broader operation to 12, 17, 18 or 19 January depending on whether they count diversionary columns, logistical movements, the two principal columns, or San Martín's own departure.

The objective immediately in front of these formations was Chile; the later expedition to Peru belonged to San Martín's wider strategy rather than to this day's marching.

The article attached to the date describes RTA 5, a twentieth-century Thai television network, and mentions neither San Martín nor the Andes.

Sources

Researched 24 Aug 2026 4 sources not yet audited Date disputed

How this was checked

Researched from the web into a fact sheet and rewritten from that sheet. This article has not yet had an independent model audit. How the pipeline works →

Date disputed. Sources disagree about when this happened.

What the sources leave uncertain

The date is secure for the two movements recorded in the operations diary, but not for the sweeping listed claim that all 5,423 men began crossing together.
San Martín's own 24 January letter says the army began departing on 18 January. Other summaries date the broader operation from 12, 17, 18 or 19 January depending on whether they count diversionary columns, logistical movements, the two principal columns or San Martín's own departure.
The figure 5,423 describes the overall army in later syntheses; it is not the number documented as leaving on 19 January.