"This afternoon I leave to join the army. God grant me success in this great enterprise."
The plan of the campaign, as drawn up by San Martin on the 15th June, 1816, was to cross the Cordillera by the passes of Uspallata and Los Patos, to re-unite his forces in the plain beyond, there to beat the principal force of the enemy and to seize the capital.
The principal spur from the main range which cuts the central valley of Chile is that which springs from the great peak of Aconcagua. From this spur a smaller one branches off, which is called the Sierra of Chacabuco, and runs parallel to the main spur, enclosing between them the parallel valleys of Putaendo and Aconcagua, watered by two streams bearing the same names, which ultimately unite to form the river Aconcagua, which empties itself in the ocean beyond the coast range of hills. The road by Uspallata passes to the south of the great peak and through the valley of Aconcagua to the frontier town of Santa Rosa. The road by Los Patos is much longer, and, passing to the north of Aconcagua, leads by the valley of Putaendo to the narrow pass of Achupallas, which lies to the west of Santa Rosa. Thus any force stationed at this point would be placed between two fires by the convergence of the two divisions, and if it retreated to the Sierra of Chacabuco which lay to the south, would leave the plain of Chacabuco available for the concentration of the army. Chacabuco was thus the strategic point upon the occupation of which depended the issue of the whole campaign.
Meantime Cabot had left San Juan on the 12th January, and on the 8th February issued from the northern passes. The whole province of Coquimbo rose in arms to welcome him. Captain Ceballos, detached by him, routed a Royalist force of a hundred men on the plains of Salala, capturing two small guns and forty prisoners. By the 12th Cabot was master of the entire province. On the same day Davila, with the detachment from Rioja, took the city of
