1461 he won Cotaxtla in the Totonac district, penetrating as far as Cozomaloapan and overrunning also the region of Tuxpan. His foreign conquests were not undisturbed by troubles in the valley, and the same must be understood of the later rulers also. Revolt was frequent, and encouraged rather than otherwise by the religious beliefs of the Mexicans, as will be explained later. In particular those cities which contained a large percentage of some formerly dominant people were perpetually seceding, and among them Chalco and Xochimilco were frequent offenders. To the east the population of Tlaxcala and Uexotzinco were a perpetual thorn in the side of the Aztec, and were never reduced to subjection. The Tlaxcalans in particular succeeded in holding their own, and their hostility to Tenochtitlan, of more than half a century's duration, proved of inestimable value to the Spaniards. This people, who as we have seen were of "Chichimec" origin, had originally been settled on the east shore of the lake, but, owing to quarrels with their neighbours, decided to move their residence. A few went north and settled in Tulanzinco, but the majority migrated east through Cholula to the region of Mount Matlalcue, whence they drove the Olmec and Xicalanga. No doubt a certain amount of intermingling took place between the peoples, and it was partly the large infusion of Toltec blood which rendered them so implacably hostile to Aztec rule, and usually on such good terms with the Cholulans. With the Uexotzinca their relations were variable, but more often friendly than not. As has been related, they assisted in the overthrow of the Tepanec power, but the expansion of Mexico under Montecuzoma was by no means to their liking, and friction soon arose. With the Uexotzinca they assisted the northern Mixtec against Montecuzoma, and succeeded at first in checking the Aztec advance in this direction. However, in twenty-nine years Montecuzoma extended the influ-
