The president had resolved that he would not go to Lima till he had completed the purposes of his mission, by the final conquest of Gonzalo and his adherents, and the restoration of peace and order in the kingdom of Peru; on which account he transmitted orders to all quarters, that all who had declared for his majesty should meet him in the valley of Jauja, which he considered to be a convenient situation in which to assemble the whole loyal force of the kingdom, as in that place abundance of provisions could easily be procured. For this purpose, he sent orders to Lorenzo de Aldana, then at Lima, to march with all his force for Jauja; and joining the army under Hinojosa, now exceeding a thousand men, he marched for Jauja, all the army expressing the utmost satisfaction at the prospect of being freed from the tyranny of Gonzalo. Many of the principal persons who had joined with Gonzalo at the beginning of the troubles, were now exceedingly offended and displeased by the cruel murders of so many of their friends and neighbours; above five hundred men having been put to death, many of whom were persons of consideration and importance; insomuch that those who still remained along with him were continually in fear of their lives.

On his arrival at Arequipa, Gonzalo found that city entirely deserted, as most of the inhabitants had gone to join Diego Centeno after that officer got possession of Cuzco. Hearing that Centeno was in the Collao, near the lake of Titicaca, where after his junction with Mendoza, he had an army of near a thousand men, composed of the troops of Cuzco Las Charcas and Arequipa, and with which they occupied all the passes towards the interior, Gonzalo believed it almost impossible to attack these officers with any probability of success. He waited therefore at Arequipa about three weeks, expecting the junction of D'Acosta, who at length arrived, but with very diminished numbers, as already related, many having abandoned him, and having put many of his followers to death on suspicion that they intended to desert. After the junction of D'Acosta, Gonzalo found himself at the head of five hundred men. He now wrote to Centeno, giving a recital of all the events which had occurred during the troubles, and dwelt particularly on the favour he had always shewn him, and particularly instanced the pardon he had granted him when Gaspard Rodriguez and Philip Guttierrez were executed, though equally guilty with them, and although all his officers had urged him to put Centeno to death. In addition, Gonzalo made high offers to Centeno, promising to accede to every demand he might choose to make, if he would now join him. He sent this letter to Centeno by a person named Francisco Vaso, who immediately offered his services to Centeno, to whom he intimated that Diego Alvarez his standard-bearer was in correspondence with Gonzalo. Centeno was already informed of this circumstance by Alvarez himself, who assured him he had entered into this correspondence for a quite different purpose than that of betraying him or the royal cause.

Centeno thought proper to send a civil answer to Gonzalo, giving him many thanks for his offers, and freely acknowledging the favour he had formerly experienced. That as a mark of his gratitude, therefore, he now earnestly entreated him to reflect seriously on the present situation of affairs, to consider the gracious clemency of the king, who had granted a free pardon to him and all those who had taken any part in the past troubles. He assured Gonzalo, if he would abandon the insurrection, now evidently hopeless, and submit to the royal orders, that he would use his utmost endeavours to procure him an honourable and advantageous situation, and at the same time endeavoured to convince him that he would run no risk either in his person or property by following the present advice. On his return to Gonzalo with this letter, Vaso was met by the lieutenant-general Carvajal, who made minute inquiry respecting every thing he had seen and learnt, and gave him strict injunctions not to let it be known to the followers of Gonzalo that the force of Centeno exceeded seven hundred men. On being informed that Centeno refused to join him, Gonzalo disdained to read his letter, and ordered it immediately to be burnt in presence of several of his officers.

Immediately after this, Gonzalo determined to march into the province of Las Charcas, and accordingly took the direct road towards the pass occupied by Centeno and Mendoza. In this march the van-guard was commanded by the lieutenant-general, who took and hanged more than twenty persons whom he fell in with during the march. Among these was a priest named Pantaleon, who carried some letters for Centeno, and whom Carvajal ordered to be hung up, with his breviary and ink-horn suspended from his neck. Continuing this march, the scouts of the two armies fell in with each other on Thursday the 19th of October 1547. Gonzalo immediately sent one of his chaplains with a message to Centeno, demanding leave to continue his march through the pass, without being obliged to give battle32. The chaplain was conducted by the bishop of Cuzco, who happened to be in the army of Centeno, to his tent; and Centeno gave strict charges to his troops to be on their guard and always in good order to receive the enemy in case of an attack. For above a month Centeno had been afflicted by an obstinate fever, for which he had been six times blooded without any relief, and was not expected to recover; so that he was quite incapable of acting on the present emergency, being confined constantly to bed.

The illness of Centeno was known in the army of Gonzalo, and that his tent was pitched at some distance from the rest, to avoid the noise and bustle of the camp. Founding on this intelligence, Juan d'Acosta was detached with twenty picked men, with orders to approach silently in the night to the camp of the royalists, and to endeavour to carry off Centeno. Acosta accordingly drew near with so much caution that he surprised the centinels that were on guard over Centeno, and had very near reached his tent when the alarm was given by some negro servants. Being thus discovered, Acosta ordered his men to fire off their musquets, and immediately retreated back to the camp of Gonzalo without losing a man. In the confusion occasioned by this exploit, great numbers of the royalists hastened towards the tent occupied by Centeno; but on this occasion several of the soldiers belonging to Valdivia threw away their arms and fled. Next morning the scouts of both armies approached each other, followed by the respective armies, which at length came in sight. The army of Centeno consisted of about a thousand men, two hundred of whom were cavalry, an hundred and fifty armed with musquets, and all the rest with pikes. Of this army, Luis de Ribera was major-general, Pedro de Rios, Jerom Villegas, and Pedro de Ulloa, captains of cavalry, and Diego Alvarez carried the grand-standard. The captains of infantry were Juan de Vargas, Francisco Retamoso, Negral, Pantoia, and Diego Lopez de Zuniga; Luis Garcias being sergeant-major, or adjutant-general33. The army of Gonzalo consisted only of five hundred men, of which three hundred were musqueteers, and eighty cavalry, the remainder being armed with pikes. Of this army Carvajal was lieutenant-general; the licentiate Cepeda and Juan Velez de Guevara were captains of horse; and Juan d'Acosta, Ferdinand Bachicao, and Juan de la Torre captains of foot.

Both armies being drawn up in good order, the insurgents advanced, to the sound of trumpets and other musical instruments, till within six hundred paces of the enemy, when Carvajal ordered them to halt. The royalists continued to advance till within a hundred paces less, and then halted likewise. At this time, forty musqueteers were detached from the army of Gonzalo, with orders to begin the engagement; and two other parties of musqueteers, of forty men each, were posted on the wings, Pizarro taking his station between his cavalry and infantry. Thirty musqueteers were likewise advanced from the army of Centeno, to skirmish with those of the insurgents. As Carvajal observed that the royalists waited the attack in good order, he ordered his troops to advance a few steps very slowly, in hopes of inducing the enemy to make some movement or evolution which might occasion confusion in their ranks. This had the desired, effect, as the royalists, believing that their enemies, though interior in number, wished to have the honour of making the attack, they began immediately to advance, and the insurgents by order of Carvajal stood firm to receive them. When tolerably near, Carvajal gave orders for a small number of his troops to fire their musquets, on which the royalists made a general discharge, and marched forwards at a quick step with levelled pikes, during which the royalist musqueteers made a second discharge without occasioning any loss to the enemy, as they were still three hundred paces distant. Carvajal made his men reserve their fire till the enemy was within about an hundred paces; when, with a few pieces of artillery, and the whole of his musqueteers, he threw in so destructive a volley that above an hundred and fifty of the royalists were slain, among whom were two of their captains. By this terrible slaughter, the whole infantry of the royalist army was thrown into disorder, entirely defeated, and took to flight, in spite of every effort of Captain Retimoso to rally them, who lay wounded in the field. Notwithstanding the defeat of the infantry, the royalist cavalry made a brave charge against the insurgents, of whom they killed and wounded a considerable number. On this occasion Gonzalo had his horse killed and was thrown to the ground, yet escaped unhurt. Pedro de Rios and Pedro de Ulloa, captains of cavalry belonging to Centeno, wheeled with their squadrons round the wing of the insurgent infantry, intending to charge their flank; but were opposed by the detachments of musqueteers which were posted on the wings, on which occasion De Rios and several others were slain. Being thus repulsed, and seeing their own infantry entirely defeated, the cavalry took likewise to flight and dispersed, every one endeavouring to save himself as he best could.