Book excerpt: In AD 1438 a battle took place outside the city of Cuzco that changed the course of South American history. The Chanka, a powerful ethnic group from the Andahuaylas region, had begun an aggressive program of expansion. Conquering a host of smaller polities, their army had advanced well inside the territory of their traditional rival, the Inca. In a series of unusual maneuvers, the Inca defeated the invading Chanka forces and became the most powerful people in the Andes. Many scholars believe that the defeat of the Chanka represents a defining moment in the history of South America as the Inca then continued to expand and establish the largest empire of the Americas. Despite its critical position in South American history, until recently the Chanka heartland remained unexplored and the cultural processes that led to their rapid development and subsequent defeat by the Inca had not been investigated. From 2001 to 2004, Brian Bauer conducted an archaeological survey of the Andahuaylas region. This project represents an unparalleled opportunity to examine theoretical issues concerning the history and cultural development of late-prehistoric societies in this area of the Andes. The resulting book includes an archaeological analysis on the development of the Chanka and examines their ultimate defeat by the Inca.