"Sometime around A.D. 900, the small-scale feuding that had characterized warfare in the American Southwest stopped. This type of conflict, in which small bands of warriors killed or kidnapped a few enemies at a time, was replaced by political violence in the form of brutal executions and possible cannibalism of whole families, women and children included. Archaeologists such as Stephen Lekson of the University of Colorado at Boulder suggest these killings were used by emerging elites centered at the massive Ancestral Puebloan sites of Chaco Canyon and later Aztec Ruins to eliminate political opponents and maintain order. But by A.D. 1250, the region-wide political systems started at Chaco Canyon failed, leaving in their wake intense, large-scale village-on-village warfare. Lekson proposes that this conflict was spurred by changing rainfall patterns that made agricultural yields unpredictable and by the 'socialization of fear' fostered by the reign of the Chacoan elites, who accustomed people to the use of force as a means of settling political disagreements. This intense warfare created unprecedented chaos in the American Southwest. Evidence for the violent end of communities abounds at sites such as Castle Rock Pueblo in Colorado, where archaeologists found the remains of 38 victims who were killed and left unburied."