In 1540, Valdivia led an expedition of 150 Spaniards into Chile, where he defeated a large force of indigenous warriors and founded Santiago in 1541.

[6]: 264  Afterwards Valdivia accompanied Hernando and Gonzalo Pizarro to conquer both the province of Collao and las Charcas in High Peru (currently Bolivia).

While Valdivia was preparing the expedition, Pedro Sánchez de la Hoz arrived from Spain with a royal grant for the same territory.

The small expedition finally left Cuzco, Peru in January 1540, with Pizarro's permission[8] and Pedro Sancho de Hoz as partner.

Valdivia resolved to avoid the road over the Andes, which had proved fatal to Almagro's army, and set out resolutely through the Atacama Desert.

Soon thereafter they continued south and in December 1540, eleven months after they left Cuzco, Valdivia and his expedition reached the valley of the Mapocho river, where they established the capital of the territory.

[10] After arriving in Chile, Valdivia and his men worked to restore a positive relationship between the conquistadores and Indians, which had been greatly harmed by Almagro and his merciless ways.

One of the first orders that Valdivia gave was to have a ship constructed at the mouth of the Aconcagua River to send to Peru for further supplies and to serve as a courier service.

On learning of Francisco Pizarro's murder in 1541, Valdivia had himself appointed governor of the territory by the council of the new city, and removed Chile from Peruvian control, acknowledging only the royal authority, an arrangement the Crown found acceptable.

Secure now in his own domain, he pushed exploration southward and aided the development of the country by dividing the land among his ablest followers and parceling out the Indians in encomiendas.

By the time the battle ended the entire town had been destroyed and burned to the ground, animals were killed and the fields and stores were decimated.

The resistance of the Native people became stronger daily, and as the ship that he had constructed in Aconcagua was also destroyed by the natives, Valdivia sent in 1542 overland to Peru his lieutenant Alonso de Monroy with five followers to seek reinforcements, but, on account of the disturbance in that country in consequence of the defeat of El Mozo Almagro by Cristóbal Vaca de Castro, Monroy could not obtain much aid, and returned in September 1543, with only seventy horsemen, also sending by sea a vessel with provisions and ammunition to the port of Aconcagua.

In September 1543 new arms, clothes and other equipment arrived from Peru on the ship Santiaguillo; thanks to these new supplies, Valdivia was in the position to start the rebuilding of Santiago and to send an expedition, led by Juan Bohón, to explore and populate the northern region of Chile.

In 1544 Valdivia sent a naval expedition consisting of the barks San Pedro and Santiaguillo, under the command of Juan Bautista Pastene, to reconnoiter the southwestern coast of South America, ordering him to reach the Strait of Magellan.

To secure additional aid and confirm his claims to the conquered territory, Valdivia returned in 1547 to Peru, leaving Francisco de Villagra as governor in his stead.

Nonetheless, early in 1548 Valdivia joined the royal army of Viceroy Pedro de la Gasca, and his military experience counted heavily in the victory of Xaquixahuana on April 9 of that year.

One of the charges levelled against him was that he, being married, openly lived with Inés de Suárez "...in the manner of man and wife and they sleep in one bed and they eat in one dish...".

[18] In exchange for being freed, and for his confirmation as Royal Governor, he agreed to relinquish her and to bring to Chile his wife, Marina Ortíz de Gaete, who only arrived after Valdivia's death in 1554.

As recognition for his services Valdivia was finally appointed as adelantado and won the royal assent to his coveted title of Governor of Chile, returning to the settlement with his position and prestige considerably strengthened.

Valdivia had a clash with the warlike Araucanians beyond the Bio-Bio River in 1550 in which he defeated them but by no means broke their will to resist, a will that grew stronger when the conquistador established settlements in their territory.

To keep the connection open between Concepción and the southern settlements, Valdivia had a number of forts built in Cordillera de Nahuelbuta.

Valdivia was at Concepcion when he received notice of this event, and, believing that he could easily subdue the uprising, he hurried southward, sallying forth with only 40 men to stamp out the rebellion.

According to Jerónimo de Vivar, an author contemporary with the events, the execution of Valdivia was personally ordered by Caupolicán, who had him killed with a lance, and later his head, and those of two of his bravest companions, were put on display.

His twelve letters, addressed to the king and mostly preserved in the archives of the Indies, are models of a vigorous and fluent style, and of great historical interest.