By AD 1000, the Colla controlled the high-altitude plains near Lake Titicaca in southern Peru. They fought over the region for many centuries before becoming a subject people of the Inca (who described them as the most formidible foes they faced) circa 1450, and then of the Spanish in the sixteenth century. Like any people at war, the Colla were not engaged in active conflict all of the time. But frequent warfare (perhaps over limited natural resources), along with drought and environmental changes, powerfully influenced the society's settlement choices and physical defenses, as well as their interaction with the landscape. By focusing on the pre-Inca society in this key region of the Andes, Elizabeth Arkush demonstrates how a thorough archaeological investigation of these hillfort towns reveals new ways to study the sociopolitical organization of pre-Columbian societies.