Receiving more certain information of the situation of the enemy, who were still at the distance of nine leagues from his camp, Vaca de Castro sent a letter to Don Diego by Francisco Ydiaquez, commanding him in his majesty's name to dismiss his army, and to repair to the royal standard, on doing which he should be pardoned for all that was past: But, if he refused, he might expect to be proceeded against with the utmost severity, as a rebel against the king. The governor sent likewise a private soldier who was well acquainted with the country, diguised as an Indian, carrying letters for several gentlemen in the rebel army, offering them an amnesty and large rewards if they would abandon Don Diego. Though this man took every precaution to prevent discovery, his track was noticed in some places in the snow, and he was followed and carried prisoner to Don Diego, who ordered him to be hanged. Don Diego complained loudly of Vaca de Castro for sending spies to corrupt his followers while making offers of accommodation; and drawing out his army in complete order before the governors messengers, he ordered all his officers to prepare for battle, promising that whoever killed any of the hostile inhabitants of the country, should be rewarded with the wife, lands, Indians, and wealth of the slain. He then gave an answer to the governors message, that he would never acknowledge or obey him so long as he was associated with his enemies, Pedro Alvarez Holguin, Alonso de Alvarado, Gomez de Tordoya, Juan de Saavedra, Garcilasso de la Vega, Yllen Suarez de Carvajal, Gomez de Alvarado, and others of that party. That he would never disband his army, unless he received a formal amnesty under the royal sign manual; as he could not give faith to one signed by the Cardinal de Loaysa. That de Castro was much mistaken in supposing any of his army would abandon him, and might therefore prepare for battle, as he was determined to defend the country to his last breath.
On receiving this resolute answer, Vaca de Castro marched his army to a small distance from Guamanga, where the ground was too rough and uneven for his cavalry, and took up a position in a smooth plain named Chupaz, where he remained three days, during all which time it never ceased raining, as it was then the middle of winter, yet the troops were forced to be always under arms and ready for action, as the enemy was very near. He had resolved to give battle, us the enemy obstinately refused all accommodation; yet finding that several persons in his army seemed to hesitate on account of the disapprobation which his majesty had evinced respecting the former battle of Salinas, on which account Ferdinand Pizarro was detained in prison, he judged it proper to take some formal judicial steps, both for his own justification, and to satisfy the scruples of his troops. He pronounced therefore a formal sentence against Don Diego, whom he declared a traitor and rebel, condemning him and all his adherents to death and the confiscation of all their goods. After signing this judicial sentence in the presence of the whole army, he commanded the officers to give him asistance for carrying it into execution.
Next morning, being Saturday, the scouts brought intelligence after mass that the enemy, who had encamped for the night at two short leagues distance, was very near, and in full march towards the left of the royalist camp, advancing by some low hills to avoid a marsh which covered the front of the royalists. Don Diego wished to gain possession of Guamanga before giving battle, and entertained no doubt of being victorious, trusting to his great superiority in artillery over the royalist army. When the two armies were so near that the advanced guards were within musket shot, the governor detached Captain Castro with fifty musqueteers to skirmish with the enemy, while the rest of his troops marched up the slope of a hill on purpose to intercept the march of the rebels. This movement was liable to considerable danger, as Don Diego might have done the royalists much damage by means of his artillery if he had taken advantage of the nature of the ground in proper time; for during this conversion, the royalist infantry were often obliged to halt to recover their order, which was much deranged by the difficulty of the ground. When Carvajal the serjeant-major observed this circumstance, he ordered all the troops to gain the height as quickly as possible without preserving any precise order of march, and to form again when they were arrived at the summit. They accordingly got all up, while Captain Castro and his musqueteers were skirmishing with the troops of Don Diego; who likewise continued his march, and drew up in order of battle.
After the royal army had been marshalled in good order by the serjeant-major, the governor made them a speech, in which he exhorted them to recollect that they were loyal Spaniards who were fighting in the just cause of their sovereign. He told them that the fate of Peru was now in their hands and depended on their courage. If defeated he and they could only expect to be put to death; but if victorious, besides the important service to the king, which they were bound as good and loyal subjects to perform, they would thereby secure the possession of their estates and effects, and to such as had none he would provide amply in the name and by the authority of his majesty, who only desired to preserve the sovereignty of Peru, that he might divide it among those who served him faithfully. In conclusion, he said there needed not a long harangue to encourage gentlemen of honour and brave soldiers to do their duty, whose example he proposed to himself to follow, not pretending to give them one; yet, as a proof that he meant to imitate their bravery, he intended to march at their head and should be among the first to break a lance. They all declared that they would do their duty manfully, and would rather be cut to pieces than allow themselves to be defeated, as they all considered themselves interested in the success of the war on their own accounts, as well as from duty to the king. All the officers earnestly intreated Vaca de Castro not to hazard himself in the front of battle, insisting that he should take post in the rear with thirty horsemen, whence he might send succour to wherever it might be needed. He consented to this, and as the day drew towards a close, being within an hour and a half of sunset, he proposed to postpone the battle till next morning. But Alonso de Alvarado assured him that he would be defeated if he delayed, as the whole army seemed then animated by the best resolution, and it was impossible to say whether some might not change their sentiments during the night. The governor assented to this advice, only saying that he wished to have the power which had been given to Joshua, that he might stop the going down of the sun.
At this time the artillery belonging to Don Diego opened its fire upon the royalists; and as it was dangerous to descend the hill in front towards the enemy, on account of being too much exposed in that direction to their guns, the serjeant-major and Alonso Alvarado directed the army to move by the left, where there was a hollow which led towards the enemy, by which they were protected from the balls which all flew over their heads. The troops marched in the following order. Alonzo de Alvarado was on the right with his troops of horse, having the royal standard carried by Christoval de Barientos; on the left were the other four captains of horse, Pedro Holguin, Gomes Alvarado, Garcilasso de la Vega, and Pedro Anzurez, all at the head of their respective troops in excellent order. Between the two wings of cavalry, the Captains Pedro de Vergara and Juan Velez de Guevara marched with the infantry; and Nunno de Castro marched in front with his musqueteers to begin the battle, with orders to retire when pressed by the enemy under the protection of the main body. The governor, at the earnest entreaty of his officers, remained in the rear guard at the head of thirty horse, at some short distance from the main body, where he could see all that occurred, so as to send assistance where it was wanted, which he did with much judgment.