In anticipation of Mendoza's invasion of their territory, the Mapuche organized their defense by gathering their forces in three places; the first was a pucará on the height of Andalicán five leagues south of Concepcion covering the approach down the coast to Arauco.

This was to draw the attention of the Mapuche while he made his real crossing using the boats of his fleet and special rafts constructed to carry his thousand horses quickly across the river.

Meanwhile, a pair of Spanish soldiers left camp without orders to gather some fruit in the nearby woods and discovered a large force of Mapuche waiting in ambush.

Upon receiving word of the approach of the Mapuche from Captain Reinoso, the governor sent him a reinforcement of fifty of his cavalry and twenty arquebusiers under Rodrigo de Quiroga.

Mendoza sent Galvarino to inform the toqui Caupolican of the number and quality of the people which had entered their land again, to put some fear into him, so that he might submit without coming to blows.