After this second action, Millalauco was sent with a message from the toqui to the Spaniards in the island of Quiriquina, whence he brought back intelligence that Don Garcia, with a large body of troops from Imperial, was laying waste the neighbouring provinces belonging to the Araucanian confederacy. On this information, and influenced by the advice of the aged Colocolo, young Caupolican deferred his proposed enterprise against Conception, and hastened into the south to oppose Don Garcia, leaving a respectable force under Millalauco to make head against Reynoso. Don Garcia however, on being informed of the march of the Araucanian array against him, withdrew to Imperial, leaving a body of two hundred of his cavalry in ambush on the road by which Caupolican had to pass. Though unexpectedly attacked by the Spaniards, Caupolican defended himself with admirable courage and presence of mind, and not only repelled the Spaniards with very little loss on his own side, but cut in pieces a great number of his assailants, and pursued the rest to the gates of Imperial, to which he immediately laid close siege. In the mean time, Reynoso and Millalauco, after several severe yet inconclusive encounters, agreed to fight a single combat, a practice not unfrequent during the Araucanian war. They fought accordingly a long while without either being able to obtain the advantage; and at length, fatigued by their combat, they separated by mutual consent, and resumed their former mode of warfare.
Caupolican prosecuted the siege of Imperial with much vigour, but possessed no means of making any impression on its fortifications. After several violent but unsuccessful assaults, he made an attempt to gain over the Promaucian auxiliaries of the Spaniards by means similar to what had been unsuccessfully employed by his father on a former occasion. Two of his officers, named Tulcamaru and Torquin, were employed on this hazardous service and detected by the Spaniards, by whom they were both impaled in sight of the Araucanian army, whom they exhorted in their last moments to die valiantly in defending the liberties of their country. At the same time, an hundred and twenty of the Promaucians, who had been seduced to favour the Araucanians, were hung on the ramparts, all of whom exhorted their countrymen to aid the Araucanians. Caupolican was anxious to siglize himself by the capture of a place which his heroic father had twice attempted in vain, and made a violent effort to carry the place by assault. He several times scaled the walls of the town in person, exposing his life to the most imminent danger, and even one night effected an entrance into the city, followed by Tucapel and a number of brave companions, but was repulsed by Don Garcia, whose vigilance was incessant. On this occasion, Caupolican withdrew, constantly fighting and covered by the blood of his enemies, to a bastion of the fortress, whence he escaped by an adventurous leap and rejoined his troops, who were in much apprehension for the safety of their brave and beloved commander. Wearied out by the length of the siege, which he saw no reasonable prospect of bringing to a favourable conclusion, and impatient of the inactivity of a blockade, Caupolican abandoned this ineffectual attempt upon Imperial, and turned his arms against Reynoso in hope of being able to take revenge upon him for the death of his father. But Don Garcia, by going to the assistance of that officer, rendered all his efforts ineffectual.
In the campaign of the following year, 1559, numerous battles were fought between the two armies, with various successes; but as these produced no material change in the state of affairs, it is unnecessary to give any particular account of them. Though several of these encounters ended in favour of the Araucanians, yet Caupolican resolved to protract the war, as his troops were daily diminishing in numbers from being continually exposed to the fire arms of their enemies, while the Spaniards were constantly receiving recruits from Peru and Europe. With this intention, therefore, he took possession of a strong situation between Canete and Conception, in a place called Quipeo or Cuyapu, which he fortified so strongly as to be defensible by a few men against any number of enemies unprovided with artillery. On being informed of this measure, Don Garcia marched thither immediately with his army in order to dislodge the Araucanian general, but observing the strength of the position, he delayed for some time making an attack, in hope of drawing the enemy from their strong ground, so that his cavalry might have an opportunity of acting to advantage. In the mean time, frequent skirmishes took place between the two armies, in one of which the celebrated Millalauco was taken prisoner, and who reproached Don Garcia so severely for his cruel manner of making war, that he ordered him instantly to be impaled. While the Araucanians were thus blockaded in their intrenched camp, the traitor Andrew had the temerity to go one day with a message from Don Garcia to Caupolican, threatening him with the most cruel punishment if he did not immediately submit to the authority of the Spaniards. Caupolican, though much enraged at seeing before him the man who had betrayed his father, ordered him immediately to retire, saying that he would assuredly have put him to death by the most cruel tortures, if he had not been invested with the character of an ambassador. Yet Andrew ventured next day to come into the Araucanian camp as a spy, when he was taken prisoner, suspended by his feet from a tree, and suffocated with smoke.
At length Don Garcia commenced his attack upon the camp of the Araucanians, by a violent cannonade from all his artillery. Caupolican and his valiant followers made a vigorous sally, and attacked the Spaniards with so much fury as to kill about forty of them at the first charge, and continued the battle for some time with much success. After a short time, Don Garcia, by a skilful evolution, cut off the retreat of the Araucanians and surrounded them on every side. Yet Caupolican and his intrepid soldiers fought with such desperate valour that the issue of the engagement remained doubtful for six hours; till, seeing Tucapel, Colocolo, Rencu, Lincoyan, Mariantu, Ongolmo, and several others of his most valiant officers slain, Caupolican attempted to retreat with the small remnant of his army: But, being overtaken by a party of horse from which he could not possibly escape, he slew himself to avoid a similar, cruel fate as that which his father had endured.
Though Don Garcia had already been mistaken in supposing that the spirit of the Araucanians was entirely broken after their terrible overthrow at Canete, he now again thought he had good reason to believe the war wholly at an end. This victory of Quipeo seemed to him completely decisive, as the nation was now left without chiefs or troops, all their principal officers, and those who chiefly supported the courage of the Araucanians, having perished, with the flower of their soldiers, so that he believed the nation would henceforwards be entirely submissive to the will of the conquerors. Impressed with these hopes, he now devoted his whole attention to repair the losses occasioned by the war, rebuilding the fortifications which had been destroyed, particularly Arauco, Angol, and Villarica, all of which he repeopled and provided with competent garrisons. He caused all the mines which had been abandoned to be reopened, and others to be explored: And obtained the establishment of a bishopric in the capital of Chili, to which place he went in person to receive the first bishop, Fernando Barrionuevo, a Franciscan monk. Having a considerable number of veteran troops under his command, for most of whom he believed there was no longer occasion in Chili, he sent off a part of them under Pedro Castillo to complete the conquest of Cujo, formerly commenced by Francisco de Aguirre. Castillo subjected the Guarpes, the ancient inhabitants of that province, to the Spanish dominion, and founded two cities on the eastern skirts of the Andes, which he named San Juan and Mendoza, the latter in compliment to the family name of the governor Don Garcia. The extensive and fertile province of Cujo remained for a considerable time dependent on the government of Chili, but has been since transferred to the vice-royalty of Buenos Ayres, to which it seems more properly to appertain from its situation and natural boundaries.