Many chiefs aspired to the glorious situation of avenger of their oppressed country, the most distinguished among whom were Andalican, Elicura, Ongolmo, Renco, and Tucapel. The last of these was so highly celebrated by his martial prowess that the province of which he was Apo-ulmen has ever since retained his name. He was besides supported in his pretensions by a powerful party; but his elevation to the supreme command was opposed by the more prudent members of the assembly, who dreaded lest the impetuosity of his character might hasten the entire ruin of the nation, instead of retrieving their honour and independence. Dissensions arose so high that the opposite parties were on the point of turning their arms against each other, when the venerable Colocolo rose to speak, and obtained a patient and attentive hearing. By a judicious and energetic address, he pacified their factious irritation so completely, that the assembly unanimously submitted the nomination of a supreme toqui to his choice. The wise old man, on whom every eye was now fixed in anxious expectation, immediately named Caupolican, the ulmen of Pilmaquen a subordinate district of the province of Tucapel, and the whole assembly applauded and confirmed the choice. Caupolican was of a lofty stature and uncommon bodily strength; and though he had lost an eye, the majesty of his countenance evinced great endowments of mind. He was of a serious, patient, and sagacious disposition; and besides great personal bravery, had every requisite to constitute him an able general of the peculiar troops over whom he was now appointed to command. On being invested with the battle-axe, as the badge of his supreme authority, he immediately selected the officers who were to bear command under him in the army of the state, among whom were all the late competitors, and even Lincoyan the former toqui. The office of vice-toqui, or lieutenant-general, he conferred on Marientu, a person in whom he reposed entire confidence. Even the violent Tucapel, who had nearly involved his country in civil war for the attainment of the supreme command, did not disdain to serve under the orders of his own vassal, manifesting by this submission his eager wish to sacrifice his personal ambition to the service of his country.

As the Araucanians believed themselves invincible under the command of their new toqui, they were desirous of going immediately from the place of assembly to attack the Spaniards. But Caupolican, no less prudent in council than valiant in the field, repressed this rash ardour, and persuaded them to disperse to their several places of abode, to provide themselves with good arms in order to be in readiness at the first summons to the field, and to leave the direction of the war to his management. Shortly afterwards, he collected and reviewed his army67, and resolved to commence his operations by a stratagem suggested by an accident. He had that morning taken eighty Indian prisoners, who were conducting forage to the Spanish garrison in the neighbouring fort of Arauco. In place of these men, he substituted an equal number of his own bravest soldiers, under the command of Cajuguenu and Alcatipay, whom he directed to conceal their arms among the bundles of grass, and to maintain possession of the gate of the fortress until he could come to their assistance with the rest of his army. The pretended foragers conducted themselves with so much judgment that they were admitted into the fortress without any suspicion on the part of the garrison, and immediately seizing their arms, they attacked the guard at the gate, killing all that came in their way. The alarm however soon spread, and the rest of the garrison hastened in arms to the spot, under Francisco Reynoso the commandant, and drove the Araucanians from the gate after an obstinate contest, at the very moment when Caupolican came up with his army, so that the Spaniards had just sufficient time to raise the draw-bridge and hasten to defend their ramparts. Though disappointed in his expectation of gaining admittance by the gate, Caupolican was still in hope of profiting from the confusion of the garrison, and encouraged his soldiers to assail the fortress on all sides, notwithstanding the continual fire kept up by the Spaniards from two cannon and six small field-pieces. After losing a great number of men in this unequal contest, Caupolican drew off from the assault, and determined to attempt the reduction of Arauco by a strict blockade, in hopes that the Spaniards would be soon constrained by famine into a surrender.

After the blockade had continued for some time, during which the Spaniards made several unsuccesful sallies with considerable loss, Reynoso determined to abandon the fort and to retire with his remaining garrison to Puren, as provisions began to fail, and there was no prospect of being relieved. Accordingly the whole garrison mounted their horses at midnight, and rushing suddenly from the gate, made their escape through the middle of their enemies. As the Araucanians supposed this to have been one of the ordinary sallies, they took no measures to obstruct their flight, and Reynoso got off with his men. Having destroyed the fort of Arauco, Caupolican led his army to attack that of Tucapel, which was commanded by Martin Erizar with a garrison of forty men. Erizar defended himself gallantly for several days; but as provisions began to fail, and his small force was continually diminishing by the perpetually renewed assaults of the enemy, he likewise determined upon withdrawing to Puren, which he successfully executed, either by similar means as those pursued by Reynoso, or in consequence of a capitulation with Caupolican. Having destroyed this fortress, Caupolican encamped with his army in the neighbourhood, to wait the approach of the Spaniards, who he supposed would not be long of coming against him with an army.

Valdivia, who then resided in the city of Conception, no sooner learnt that the Araucanians had besieged Arauco, than he began his march for that place with such forces as he was able to collect at a short notice; though contrary to the advice of his most experienced officers, who urged him to wait till he could collect a more formidable army, and seemed to have a presentiment of the fatal consequences which were to result from the present expedition. The historians of the times differ materially in their accounts of the force under Valdivia on this occasion. According to some of these his army consisted of two hundred Spaniards and five thousand Promaucian auxiliaries, while others reduce the number to a half. The same uncertainty is to be found respecting the number of the enemy, some estimating them at nine and others at ten thousand men68. On approaching the encampment of Caupolican, Valdivia sent forwards a detachment of ten horsemen under Diego del Oro to reconnoitre, all of whom were slain by the enemy, and their heads cut off and hung upon trees by the way in which the Spanish army had to advance. On arriving at this place, the Spaniards were filled with horror at this miserable spectacle, and many of them, in spite of their usual intrepidity, were eager to retreat till a greater force could be collected. Even Valdivia regretted that he had not conformed to the advice of his older officers; but encouraged by the boasting confidence of others, who proudly declared that ten Spaniards were sufficient to put the whole Araucanian army to flight, he continued his march and came in sight of the enemy on the 3d of December 1553. The prospect of the ruins of Tucapel and the well regulated array of the adverse army, with the insulting taunts of the enemy, who upbraided them as robbers and impostors, filled the minds of the Spaniards, hitherto accustomed to respect and submission from the Indians, with mingled sentiments of dread and indignation.