When Cuauhtemoc is elected tlatoani in 1520,…
December 1520 CE
In keeping with traditional practice, the most able candidate among the high noblemen is chosen by vote of the highest noblemen, and Cuauhtemoc assumes the rulership.
Although under Cuitlahuac, Tenochtitlan begins mounting a defense against the invaders, it is increasingly isolated militarily and largely faces the crisis alone, as the numbers of Spanish allies increase with the desertion of many polities previously under its control.
Cuauhtemoc does not enter the historical record until he becomes emperor.
His birth date is unknown.
He is the eldest legitimate son of emperor Ahuitzotl and may well have attended the last New Fire ceremony marking the beginning of a new fifty-two-year cycle in the Aztec calendar.
Like the rest of Cuauhtemoc's early biography, this is inferred from knowledge of his age, and the likely events and life path of someone of his rank.
Following education in the calmecac, the school for elite boys, then military service, he had been named ruler of Tlatelolco, with the title cuauhtlatoani ("eagle ruler") in 1515.
To have reached this position of rulership, Cuauhtemoc had to have been a male of high birth, and a warrior who had captured enemies for sacrifice.