Since signing a treaty ceding territory was rejected, Chile was obliged to eliminate all resistance in order to force peace under its terms.

In April, the Letelier expedition was sent by train to Chicla, from where it was planned to move onto Cerro de Huasco and Huancayo seeking to seize control of the Junín Department.

Taking advantage of this strategy, these garrisons were surrounded by thousands of Indian montoneras which rose against the Chilean Army after suffering several abuses by Letelier's forces.

It became essential to the Chileans to reorganize the troops, gather them up and withdraw as soon as possible to north in order to fall back from the mountains, avoiding a possible defeat.

The chosen rendezvous point for the retreat was the mountain pass of Las Cuevas, which needed to be guarded until the division arrival to ease the crossing to Casapalca.

After a perilous march, the Chileans reached their destination, establishing on a nearby farm called Hacienda Sángrar in order to secure shelter from the wind chill and the snow.

The farm was property of Norberto Vento, who manages to make Caceres send officers with their Indian montoneras to eliminate the trespassers.

Meanwhile, Letelier had to retreat due to extremely bad weather conditions to La Oroya, passing through Piedra Parada to Casapalca, leaving Araneda isolated and waiting for troops that will never arrive.

After many hardships, Vento's forces began to come down from Colac's Throat, encountering with Bisivinger's patrol, killing all of them after a short but fierce fight before giving any signal of the attack.

Several hundreds of Indians climbed the hills trying to assail the soldiers at Las Cuevas, but were repelled by Blanco, who waited for the proper time to rendezvous with the rest of the detachment at the farm, but the attacker's flow is steady, cutting any escape routes.

A similar thing occurred at Sángrar, where the combat is very harsh, until the Peruvians withdrew to regroup, giving the Chileans a rest for a while.

Araneda wrote a letter to himself, signed by Letelier, saying that the latter with his division will arrive at Sángrar that day, and threw it near to the Peruvian position, who hopefully would believe it.

After this encounter, the Chilean division abandoned the Peruvian sierra through Chicla and returned to Lima, where Patricio Lynch was in charge now of the occupation.