Itzcoatl

The transformation of Tenochtitlan from tributary town to imperial capital took place largely within the thirteen-year reign of Itzcoatl, the fourth tlatoani, who ruled from 1427 to 1440. A son of the founder Acamapichtli — born, according to the chronicles, to a woman of low rank, perhaps a slave from Azcapotzalco — he was passed over in earlier successions in favor of his half-brother Huitzilihuitl and then his nephew Chimalpopoca, serving instead as a military commander. When Chimalpopoca died in 1427 amid the succession crisis that followed the death of the Tepanec ruler Tezozomoc, the Mexica nobility elected the aging Itzcoatl, by then a man of long experience.

His accession brought immediate confrontation with Azcapotzalco, whose new ruler Maxtla pressed hostile demands on Tenochtitlan. Itzcoatl allied with Nezahualcoyotl, the exiled heir of Texcoco, and with the Tepanec town of Tlacopan, and around 1428 their combined forces defeated Azcapotzalco. The arrangement among the three victors hardened into the Triple Alliance, the political framework of the Aztec empire for the next ninety years, with Tenochtitlan as its leading member.

The remainder of the reign consolidated this victory. Mexica armies subdued Coyoacan and other former Tepanec dependencies, then turned south against the chinampa towns of Xochimilco, Cuitlahuac, and Mixquic, securing the agricultural wealth of the southern lakes. At home, Itzcoatl restructured Mexica society, distributing conquered lands to the nobility and elevating the warriors and counselors who had supported the war. The chronicles attribute much of this program to his nephew Tlacaelel, who held the office of cihuacoatl, a kind of chief minister. Itzcoatl is also remembered for ordering the burning of older painted histories and the composition of new ones presenting the Mexica past in a manner suited to their new supremacy — a measure that complicates every modern attempt to reconstruct the earlier chronology, including the conventional dates of his own life, roughly 1380 to 1440.

At his death in 1440 the election fell to his nephew Moctezuma I, son of Huitzilihuitl, continuing the practice by which the throne circulated among the descendants of Acamapichtli. Itzcoatl's own line remained central to the dynasty: his grandson Axayacatl and the latter's brothers Tizoc and Ahuitzotl all later ruled Tenochtitlan.