This important victory, which was gained in the evening of the 3d December 1553, was celebrated next day by the Araucanians with all kinds of games and diversions, which were exhibited in a meadow surrounded by high trees, on which the heads of the slaughtered enemies were suspended as trophies of the victory. An immense concourse of inhabitants from all the surrounding country flocked to Tucapel to enjoy the triumph obtained over an enemy hitherto considered as invincible, and to join in the festivities on this joyful occasion. In token of triumph, the Araucanian officers dressed themselves in the clothes and armour of their slain enemies, and Caupolican decorated himself with the armour and surcoat of Valdivia, which was magnificently embroidered with gold. After the conclusion of the rejoicings, Caupolican presented Lautaro to the national assembly or Butacayog, which had met to deliberate upon the proper measures to be pursued in farther prosecution of the war; and, after a speech in which he attributed the whole success of the late glorious battle to the young warrior, he appointed him extraordinary vice-toqui, and to enjoy the command of a second army which was to be raised for protecting the frontiers against invasion from the Spaniards. In consideration of the inappreciable service he had rendered to his country, the advancement of Lautaro to this new dignity was approved and applauded by all the chiefs of the confederacy. Besides the nobility of his origin, as he belonged to the order of ulmens, Lautaro was singularly beautiful in his appearance, and conciliating in his manners, and possessed talents far surpassing his years, so that in the sequel he fully confirmed the sentiments now entertained of him by Caupolican and the rest of his countrymen.
The sentiments of the assembled chiefs in respect to the farther prosecution of the war, were various and discordant. Colocolo and most of the Ulmens were of opinion, that they ought in the first place to endeavour to free their country from the remaining Spanish establishments within its bounds, before attempting to carry their incursions to the north of the Biobio. Tucapel and some others of the most daring officers, insisted that they ought to take advantage of the present circumstances to attack the Spaniards even in the city of St Jago, the centre of their colonies, while in a state of consternation and dismay, and to drive them entirely from the whole kingdom of Chili. Caupolican applauded the heroic sentiments of Tucapel, yet adopted the council of the elder chiefs, as the most prudent and beneficial for the interests of the nation.
About this time Lincoyan, the former toqui, who was at the head of a detached body of troops engaged in harassing the dispersed settlements of the Spaniards in Araucania, fell in with a party of fifteen Spaniards, on their march from Imperial to join Valdivia, of whose total defeat they had not yet received intelligence. Before engaging with the enemy, whom they confidently expected to defeat with the utmost facility, these Spaniards vainly regretted that their number exceeded twelve, in hope that the event of the day would stamp upon their names the chivalrous title of the twelve of fame. Their wishes were soon more than gratified, as seven of them fell at the first encounter with the enemy, and the remaining seven, taking advantage of the swiftness of their horses, escaped severely wounded to the fortress of Puren, carrying with them the melancholy intelligence of the total destruction of Valdivia and his army. On this distressing news the Spanish inhabitants of Puren, and Frontera or Angol, retired to Imperial, where they considered themselves in greater security than in these other more inland fortresses, which were entirely surrounded by the country of the victorious enemy. About the same time the inhabitants of Villarica abandoned that settlement and took refuge in Valdivia; so that two Spanish establishments only now remained in the Araucanian country, and both of them at a great distance from reinforcements or assistance. As Caupolican determined upon besieging these two cities, he committed to Lautaro the charge of defending the northern frontier against invasion, and set out for the south to reduce the cities of Imperial and Valdivia.
The young and gallant vice-toqui, Lautaro, accordingly took post on the lofty mountain of Mariguenu, which intervenes between Conception and Arauco, and which he fortified with extraordinary care, rightly judging that the Spaniards would take that road in search of Caupolican on purpose to revenge the defeat and death of their general Valdivia. This mountain, which has proved fatal to the Spaniards on several occasions in their wars with the Araucanians, has a large plain on its summit interspersed with shady trees. Its steep sides are full of rude precipices and deep clefts or ravines, its western end being rendered inaccessible by the sea, while on the east it is secured by an impenetrable forest. The north side only was accessible to the Spaniards, and even in that way it was only possible to reach the top by a narrow and winding path.
The two Promaucians who alone had escaped from the fatal battle of Tucapel, by favour of the darkness and under covert of a thick wood, reached Conception, which they filled with grief and consternation, by relating the total overthrow and massacre of the army of Valdivia. When the general terror and dismay had a little subsided, the magistrates proceeded to open the sealed instructions which had been left with them by Valdivia, when he departed on his late fatal expedition. In these he named Alderte, Aguirre, and Villagran successively to the vacant government in case of his own decease. Alderte being gone to Europe, and Aguirre absent on his expedition into the distant province of Cujo, the command devolved on Villagran. After such preparations as appeared necessary under the present emergency, Villagran crossed the Biobio with a considerable army of Spaniards and Promaucian auxiliaries, intending to march for Arauco in the first place. In a narrow pass at no great distance to the south of the Biobio, he was vigorously opposed by a body of Araucanian warriors, who withstood the utmost efforts of his army for three hours, and then withdrew continually fighting, towards the top of the mountain where Lautaro awaited the approach of the Spaniards with the main body of his army, in a well chosen post defended by a strong palisade. Villagran ordered the squadrons of cavalry to force their way up the difficult passage of the mountain, which they effected with infinite difficulty and severe fatigue, and were received at a short distance from the summit by showers of stones, arrows, and other missiles, which were incessantly discharged against them by the vigilant and brave Araucanians. Villagran, who followed his cavalry at the head of all the infantry of his army, with six pieces of artillery, seeing the determined opposition of the enemy, several detachments of whom were endeavouring to gain his flanks and rear, ordered his musquetry to advance, and the artillery to take a favourable position for annoying the enemy.
The mountain was enveloped in smoke, and resounded on all sides with the thunder of the Spanish cannon and musquets, while the balls were heard whistling in every direction, and dealing destruction among the ranks of the valiant Araucanians, who continued vigorously to defend their post, undismayed at the numbers who fell amid their thick array. Perceiving that his principal loss was occasioned by the cannon, Lautaro gave orders to one of his bravest officers, named Leucoton, to sally from the camp with a select detachment of troops, and to gain possession of the cannon at all events, or never more to appear in his presence. Leucoton executed his orders with the utmost bravery, and after a furious and bloody contest with the guard of the guns, carried them off in triumph; while Lautaro, to prevent the Spaniards from sending succours to their artillery, made a furious general attack on the whole line with all his troops. Astonished by this bold and general attack, and dismayed by the loss of their cannon, the Spanish horse and foot fell into confusion and disorder, and were so furiously pressed upon by the valiant Lautaro and his troops, that they dispersed and fled with the utmost precipitation. Three thousand of the Spaniards and their Promaucian allies were slain in this decisive battle, Villagran himself, having fallen in the retreat, was on the point of being taken prisoner, when he was rescued by the almost incredible efforts of three of his soldiers, and remounted on his horse. The remaining Spaniards urged on their almost exhausted horses to regain the narrow defile where the engagement had commenced, and were closely pursued by the Araucanians; but on arriving at the pass, they found it blocked up with trees, which had been felled across by orders of Lautaro. The engagement was renewed at this place with the utmost fury, and not a man of the broken army would have escaped, had not Villagran opened the pass at the utmost hazard of his life. Though the Araucanians had lost above seven hundred men in the course of this eventful battle, they continued the pursuit a long way; but at length, unable to keep up with the horses, and exhausted with excessive fatigue, they gave up the pursuit, and Lautaro encamped for the night to refresh his men, determined upon passing the Biobio next day to follow up the consequences of his glorious and decisive victory.