José de San Martín, having been instrumental…

José de San Martín, having been instrumental in the establishment of a popularly elected congress in Argentina, had begun in 1814 to consider the problem of driving the Spanish royalists from South America entirely.

Realizing that the first step would be to expel them from Chile, he had set about recruiting and equipping an army.

In just under two years, he had raised an army of some five thousand four hundred and twenty-three men, twelve hundred horses and twenty-two cannons.

Setting out from Mendoza—at this time part of the Province of Cuyo—on January 19, 1817, their goal is to enter royalist-held Chile without being noticed, through unexpected paths, so as to attack the royalist forces by surprise.

The ultimate objective is the liberation of Chile from Spanish rule with Argentine forces.

Led by José de San Martín, the crossing takes twenty-one days.