Río Biobío
Initially, the key area of conflict that the Spanish attempted to secure south of Bío Bío River were the valleys around Cordillera de Nahuelbuta. The Spanish designs for this region was to exploit the placer deposits of gold using Mapuche (slave) labor from the densely populated nearby valleys. To serve the Spanish in gold mining was a deadly activity that killed many Mapuches. Lacking a tradition of forced labor like the Andean mita the Mapuches largely refused to serve the Spanish setting the stage for the conflict.