The Mapochians continued at intervals to annoy the colony for six years, after which being utterly defeated they destroyed their crops and habitations and retired to the mountains.
Valdivia being harassed by the natives as well as by the mutinous conduct of his men, sent messengers to Peru for succour, and to show the riches of the country he caused the bits, spurs and stirrups of his two messengers to be made of gold; but they were intercepted in their route by the Copiapins, from whom they did not escape till after a length of time, and arriving in Peru where Vaca de Castro was governor, who immediately dispatched succours by sea and land to Valdivia; with this assistance he reduced some of the surrounding tribes and founded Serena or Coquimbo, in 1544.
In 1545 he entered into a treaty with the Promaucians, who thenceforward became allies of the Spaniards, and in 1546 he passed the river Maule and reduced the natives from that river to the Itata; here he was however attacked by the Indians, and forced to retreat to Santiago, from whence, hearing of the civil wars in Peru, he went to that country, leaving Francisco Villagran governor in his absence.
Valdivia acted so meritoriously under De Gasca in Peru, that after Gonzalo Pizarro was subdued the president sent him back to Chili, with the title of Governor, abundance of stores, and two ships filled with soldiers.
The Coquimbans and Copiapins having revolted, the governor sent Francisco Aguirre against them, who succeeding in his expedition, rebuilt the city of Coquimbo, in a more convenient place in 1549.
Nine years from this period were passed in constant exertion by the governor, before he could consider his power as fully settled in the northern provinces of Chili; when having distributed the lands and Indians among his followers, he turned his arms against the southern portion of his government, and after a march of 250 miles, arrived at the bay of Penco or Concepcion, where he founded the city of Concepcion, on the 5th of October, 1550. No sooner had he colonized this settlement, than the toqui or chief of the Araucanians, attacked him with an army of 4000 men; but after a battle of several hours, Aillavalu, the toqui, was slain, and the Araucanians forced to retreat. In the following year, 1551, Valdivia was attacked in Concepcion, by Lincoyan, the new toqui, or general of the Araucanians, but they retreated, after displaying much valour.
Valdivia now occupied himself in strengthening his post, and having received succours from Peru, he marched into Arauco, where, arriving at the river Cauten, he founded the city of Imperial, after which he traversed the country to the territory of the Cunches, in which he founded the town of Valdivia; and satisfied with his success, returned to St. Jago, having fought several battles with the natives, in which his troops were always victorious.
He now dispatched Aguirre, with 200 men to conquer Cuyo and Tucuman, and returning with fresh troops into Araucania, he built the city of La Frontera; and having effected this object, retired to Concepcion, and dispatched a messenger to Spain, with an account of his conquests, a solicitation of the government, and of the title of Marquess del Arauco, and he sent Francisco de Ulloa by sea, to explore the Straits of Magellan, by which he hoped to carry on a communication with the mother-country, independent of Peru.
Occupied with these affairs, he did not perceive the increasing power of the Araucanians, who having deposed Lincoyan, elected Caupolican, a warlike chief, to the supreme command of their army.
Caupolican then attacked the fort of Arauco, which the Spaniards abandoned in the night; he also compelled them to evacuate Tucapel, both of which he destroyed. Valdivia immediately collected what force he could, marched against him, but sending an advanced guard of ten horsemen to reconnoitre, they were cut off, and their heads fixed in the road through which the Spanish army was to pass. This army arrived in sight of the Araucanians, on the 3d of December, 1553, when a fierce contest immediately commenced. The Araucanians were put to flight, but in their confusion, a young chief who had been baptized and employed as page to Valdivia, suddenly deserted the Spanish army, and brandishing a lance, called out to his countrymen to turn and follow his example; this so encouraged the enemy, that they immediately commenced a fresh attack, with such success, that the Spaniards and their Promaucian allies were cut to pieces, only two of the latter escaping.