Excerpts from Books and Wikipedia
"In 1438, the Chanca people were attacking the Inca capital of Cuzco and threatened to take it, but they were fought off by Pachacutec, the principal architect of the empire who ruled from 1438 to 1471, and his men. . . . This victory was the springboard for Inca expansion. Pachacutec extended his sway over much of the Peruvian highlands and rebuilt the great temple of the sun in Cuzco. . . . The population of the empire is thought to have been as high as ten million." [1001 Days]