Much gratified with the prosperous issue of his voyage, the zealous missionary returned to Chili in 1612, carrying a letter written by the king of Spain to the national assembly of the Araucanian chiefs, recommending the establishment of peace between the nations, and that they should promote the propagation of Christianity among their dependents.  Immediately on his arrival in Chili, Valdivia hastened to the frontiers, and communicated the nature of the commission with which he was entrusted to the Araucanians, by means of some prisoners of that nation whom he had purposely brought with him from Peru.  Aillavilu the toqui gave little attention to the proposed negociation, which he deemed a feint for deceiving and surprising him.  But, as he died or resigned the command soon after, his successor Ancanamon thought proper to inquire into the reality of the pacific proposals, and directed the ulmen Carampangui to converse with Valdivia, that his offers might be laid before a general assembly of the ulmens.  Accordingly, on the invitation of Carampangui, Valdivia repaired to Nancu in the province of Catiray, where, in an assembly of fifty Araucanian chiefs, he made known the substance of the proposed pacific negociations, read and expounded the royal letter to the Araucanian confederacy, and made a long oration on the motives of his interference and on the important concerns of their immortal souls.  The assembly thanked him for his exertions, and promised to make a favourable report to the toqui.  On his return to Conception, Valdivia was accompanied by Carampangui, where he was honourably received by the governor; who dispatched Pedro Melendez one of his ensigns, under the safeguard of the ulmen, on a message to the toqui, carrying with him the letter of the king of Spain, and a request that Ancanamon would meet him at Paicavi, a place near the frontiers, that they might confer together upon the preliminaries of peace.

The toqui soon afterwards came to the place appointed, with a small guard of forty soldiers, and accompanied by several ulmens, bringing likewise along with him a number of Spanish prisoners of the first families, whom he set at liberty.  The governor, with Valdivia and the principal officers of the government, received Ancanamon with every demonstration of respect, and conducted him to the lodgings appointed for his reception amid the repeated discharges of artillery.  The governor then proposed, as preliminary articles of peace, that the river Biobio should serve hereafter as the common boundary between the Spanish and Araucanian nations, beyond which neither should be permitted to pass with an army:  That all deserters should in future be mutually returned:  And that missionaries should be allowed to preach the doctrines of Christianity in the Araucanian territories.  Ancanamon required as a preliminary, that the forts of Paicavi and Arauco, which had been lately erected upon the sea coast to the south of the Biobio, should be evacuated.  The governor immediately abandoned Paicavi, and agreed to give up the other immediately after the conclusion of peace.  Being so far agreed, and as the consent of the four toquis of the uthalmapus was requisite to ratify the treaty, Ancanamon proposed to seek for them in person, and to bring them to the Spanish camp.