But if the political power was concentrated in Tenochtitlan, Tezcoco under the wise rule of Nezahualcoyotl became the intellectual and artistic centre of the valley. The government was reformed, and a code of laws drawn up which was regarded as the pattern of all legislation; schools were instituted for the study of poetry, astronomy, music and painting, and the city was embellished by the construction of temples and gardens. However the fall of the Tepanec did not bring peace to the valley; many cities began to be jealous of the Aztec and their newly-acquired hegemony, and the Mendoza codex gives a list of cities which were conquered during the reign of Itzcoatl, among them Quauhtitlan, Cuitlauac, Xochimilco, Chalco, and Quauhnauac (Cuernavaca). Yet these "conquests" were not on the same scale as that of Azcapotzalco; from this time forward the Aztec were content with exacting merely a nominal submission from the towns which they subdued, and imposing tribute. As long as the latter was paid punctually no interference was made either with the local rulers or their administration, though theoretically the heir of a "king" who died was supposed to seek confirmation in his office at the hands of the ruler of Tenochtitlan.
With the advent to the throne of Montecuzoma, the first of that name, in 1440, the Aztec continued to extend their power beyond the valley. After a short campaign against the Chalca, in order to obtain prisoners to sacrifice at his coronation, this king proceeded to attack the region around Cuernavaca, subduing, among other towns, that of Tepoztlan, where a temple still remains inscribed with his name (S.S.W. of Cuernavaca), Yauhtepec and Tlaxco (PI. XIV, 2; p. 174). Further south, he conquered Coixtlahuaca in Mixtec territory, but his operations to the east were more extensive. In 1458 he sent an expedition into the Panuco valley, against the Huaxtec, and in
