Times of Trouble:
The order imposed by Teotihuacán’s dominance during the Classic period gave way to a fragmentation of power among the transition centers. Details of history in the Valley of Mexico are nebulous from A.D. 650 to 900, but one has the impression of confusion and a great shifting of peoples in the waning decades of the Classic, when aggressive city-states— Cholula, Xochicalco, and El Tajín—vied for control, but none succeeded in bringing about unity and order. Then gradually a new period emerges, with more secular and more martial characteristics.
The Post-Classic era began about A.D. 900 and lasted until the Spanish Conquest in the early sixteenth century. New states had significant commercial interests, as evidenced by the expansion of market systems. Long-distance exchange tended to make artistic styles more uniform and less imaginative. New technology could be seen in cotton quilted armor and the bow and arrow, but, in general, technological innovation slowed. Although metallurgy was introduced, probably from South America, its use was very limited. Gold and silver were fashioned into beautiful jewelry and copper was used in the manufacture of various tools and to cover the tips of arrow shafts.
An even more striking change during the Post-Classic was that the militaristic propensities of the Late Classic continued to grow, enhancing the prestige of warriors and fostering the conquest of tribute-paying subjects. Religion itself was marked by the rising importance of frightful gods thought to require ever-increasing quantities of the “divine liquid”—human blood. Human sacrifice proliferated as both elites and commoners became convinced that only the offering of massive and sustained quantities of this life force to the gods could prevent cosmic disaster.
Taking A.D. 900 as the pivotal date introducing the Post-Classic, we discern the emergence of historical central Mexico; for while earlier history must be deduced cautiously from archaeological evidence alone, there are in this period the beginnings of written records in