The Aztecs, convinced that the Spaniards would never return to Tenochtitlan, celebrated their fiestas again in the traditional manner, and Cuitlahuac was elected king to succeed his brother Motecuhzoma. The Aztec kings were chosen by acouncil of four lords, representing the four quarters, or phratries, into which the twenty clans of the city were evenly grouped. The council attempted to choose the wisest and bravest man among the brothers, sons and nephews of the previous ruler. Their choice of Cuitlahuac may have been influenced by the fact that he had warned against allowing the Spaniards to enterTenochtitlan (Chapter 7).
This period of normalcy was soon ended by the terrible plague that quickly spread through the city. The plague seems to have been an epidemic of smallpox, which was previously unknown among the Indians. One of its victims was the new king himself. Shortly afterward, the Spaniards reappeared. They had rebuilt their army in Tlaxcala and marched to Tlacopan by way of Tezcoco.
A number of indigenous documents describe the siege of the Aztec capital. We have chosen the account given by Sahagun's native informants in the Codex Florentino.