Bolívar took advantage of the absence of Valdés to commence operations, and marched on Jauja by the road which had twice led Arenales to victory, covering his advance by a cloud of Peruvian guerillas, under whose protection Sucre marked out the daily route of the army, and provided supplies. Bolívar ascended the range at its highest point in the direction of Pasco, hoping to surprise the enemy, and on the 2nd August passed 9,000 men in review about twenty-five miles from that city, on which occasion he was accompanied by O’Higgins and by Monteagudo, who had returned from exile. On the 4th Miller, who had been detached with a party of cavalry, brought word that Canterac was advancing from Jauja with all his army.
To the south of Pasco, at the head-waters of the Rio Grande, commences the great lake of Reyes, which lies between the two ranges of the Cordillera, and occupies all the low ground as far as the entrance of the valley of Jauja. On its eastern bank there runs a level road, on the western bank is another which leads to Junin, and is much rougher. At the southern extremity of the lake lies the plain of Junin, broken by numerous hillocks, and cut up by streams and marshes filled by the overflow from the lake.
On the 1st August Canterac had advanced with his cavalry along the eastern road to reconnoitre, and learned to his surprise that Bolívar was already on the other side of the lake. He retreated rapidly, and rejoined his infantry on the 5th August. On the 6th, at two o’clock in the afternoon, he found himself face to face with the Patriot army on the plain of Junin. Their infantry held the heights beyond, while their cavalry appeared about to charge him. Bolívar had marched along the eastern slopes of the western range, halting only in strong positions, showing a cautiousness which was not usual with him. On seeing the Royalist army, he sent Necochea in front with 900 horse. The ground was so contracted by a hill on one side and by a marsh on the other, that at five o’clock Necochea had only two squadrons of Columbian horse on the plain, when he was attacked by the whole of the Royalist cavalry, 1,300 strong, led by Canterac in person.
The Columbian lancers received the charge with great steadiness, but were driven back upon their supports, who were still entangled in the defile. The Royalist horse, greatly disordered by their rapid advance, entered the defile with the fugitives. Necochea, pierced by seven lance wounds, was trampled under foot and made prisoner. Colonel Suarez, with the first squadron of Peruvian hussars, had drawn his men into an angle of the marsh, and, letting the rout pass by, charged the pursuers in the rear. The fugitives were rallied by Miller, who led them again to the charge, and drove the Royalists from the field. In forty-five minutes the whole affair was over, and not a shot was fired. The Royalists lost 250 killed by lance and sabre; the Patriots lost 150 between killed and wounded, and rescued Necochea. The fugitives took shelter under the fire of their infantry, which at once retreated.
Such was the celebrated action of Junin, which broke the prestige of the Royalist army, and prepared the way for the final triumph. Bolívar, who had seen the rout of the first squadrons, thought he had lost his cavalry, and returned to the infantry, who were a league behind. He only learned the defeat of the enemy from a pencil note sent him by Miller after sundown. The hussars who did such good service were afterwards styled the Hussars of Junin, in reward for their gallant behaviour.
Canterac, who was greatly disheartened by this disaster, which was chiefly the result of his own precipitate conduct in charging without a reserve over ground of which he knew nothing, evacuated the valley of Jauja, and retreated so rapidly that in two days he was more than a hundred miles from the scene of the action, and his infantry was quite worn out; but he did not stop until he had crossed the Apurimac, more than five hundred miles from Junin, and lost between 2,000 and 3,000 men by desertion on the way. La Serna sent him a reinforcement of 1,500 men, and recalled Valdés to Cuzco. Canterac had fled from his own shadow, for he was not pursued.
Bolívar rested for three days on the field of battle, took ten days to occupy the valley of Jauja, and remained nearly a month at Huamanga. In September he crossed the river Pampas, an affluent of the Apurimac, and threatened Cuzco from the sources of that river, his right flank being covered by a spur from the Cordillera, but did not consider himself strong enough to attempt anything more now that the rainy season was at hand. He also learned that a loan, projected by San Martin, had been successfully launched in London, and that a million dollars were expected immediately. Leaving Sucre in command, he returned to Lima in October.
Before leaving he received notice that on the 28th July the Congress of Columbia had abrogated the law conferring extraordinary powers upon him, which he might no longer exercise now that he was in a foreign country. This was the first sign of Parliamentary resistance to his autocratic tendencies. The Liberals now formed a powerful party in Congress under the leadership of Vice-President Santander, who thought more of the interests of New Granada than of those of the Republic at large.
Bolívar received the blow with dignity, comprehending that he had brought it upon himself by taking charge of the government of a foreign state, and notified Sucre that he would only interfere in military operations as President of Peru. Sucre, who was not ambitious, and was devoted to Bolívar, advised him to pay no attention to the new law, and declared that he himself would have no direct communication with the Government of Columbia, looking to Bolívar alone for orders. Both kept their promises, Bolívar leaving complete liberty of action to Sucre, who followed his instructions except in the conduct of military operations, in which he knew that his talents were superior to those of the Liberator.
Bolívar again established his head-quarters at Pativilca, but found matters much changed for the worse. The arrival of the Spanish ship-of-the-line Asia and of the 20-gun brig Aquiles had given the naval preponderance to the Royalists. These ships were joined by a corvette and a brig from Chiloe, and there was one brig already at Callao, which Guise had failed to capture. After an exchange of shots with the Spaniards, Guise, with the Peruvian squadron, was forced to seek shelter at Guayaquil.