[3] Over time, the Chilean thought of a Bolivian or Peruvian offensive to the “Loa Line” was diluted, due to the harsh conditions to cross the Atacama Desert, so the territory lost relevance as a war front.

[2] But Chilean forces stationed in the area had to face the Bolivian locals, who were organized in montoneras to resist the occupation, hoping to see the Campero Division arrive.

[4] Some Bolivians defeated in Calama dispersed through San Pedro de Atacama and then grouped with the locals, forming a montonera of forty men[5] moderately armed with rifles.

[4] On 6 September, in one of the raids of the Bolivian montonera, the Chilean arriero Francisco Vilches was taken prisoner by these near San Pedro de Atacama, but managed to escape by the pleas of a woman when they wanted to execute him.

[6] At dawn the next day, Toro and his forces arrive at the entrance of a rough hillside in the gorge of Rio Grande, where Bolivians were hiding on top among huge rocks.