It was not until the reign of the eighth emperor, Viracocha (Hatun Tupac Inca), that the Inca became an actively expansionist tribe with an imperialist policy. Peru was populated by several strong independent tribes. In the Andean area there were three major tribes: the Lupaca and the Colla were both Aymara-speaking tribes who inhabited land around Lake Titicaca, and the Inca who ruled the Cuzco region. With all three having the power to conquer the others, it was inevitable one tribe would want to dominate the rest.
The [G 14 / Quechua] tribe occupied the land immediately to the west of Cuzco. They were related to the Inca by language, culture and blood and had an alliance with them. The Chanca tribe lay about 60 miles west of Cuzco and were enemies of both the Quechua and the Inca. Early in Viracocha's reign, the Chanca overcame the Quechua.
In 1438, the Chanca fought against the Inca and after winning several battles, they advanced on Cuzco with a large army. Viracocha and his heir, Urcon, barricaded themselves into a fortress, believing the city to be already lost. However, the two younger royal sons, Roca and Cusi Yupanqui, refused to give up and heroically defended the city. With their victory, the Chancas were no longer a threat to the expanding Inca.
This battle became legendary and was told by each generation of Inca to their children.
