The conflict between the Pizarro brothers and Almagro originated in a dispute over the possession of the city of Cuzco during the initial Spanish partition and administration of Peru.

[3] Almagro's enterprise had won him several earlier battles, but although he succeeded in taking the city by a coup de main, Pizarro's forces were by far the strongest in the region, leaving him with few options for its defence.

His cavalry was outmatched by Almagro's strong force of seasoned cavaliers, but in addition to veteran conquistadors he could rely on a contingent of Imperial arquebusiers recently arrived from Santo Domingo.

An epic shock followed as the two bodies met at full gallop, the men variously shouting "¡El Rey y Almagro!"

Almagro's infantry, meanwhile, stood no chance against the superior firepower of Pizarro's men and, after an hour of brave fighting, began to scatter in the direction of Cuzco.

Almagro watched the rout from his litter on a hill: "With an agony not to be described, he had seen his faithful followers, after their hard struggle, borne down by their opponents till, convinced that all was lost, he succeeded in mounting a mule, and rode off for a temporary refuge to the fortress of Cuzco.