Final answer:
The response of the Aztec under Moctezuma to the natural disasters of the mid 15th century led to the downfall of the Aztec civilization. Signs and omens were seen as foretellings of the Aztec's destruction. The introduction of diseases by the Spanish, such as smallpox, further weakened the Aztecs and led to their defeat.
Step-by-step explanation:
The response of the Aztec under Moctezuma to the natural disasters of the mid 15th century was significant in the downfall of the Aztec civilization. Moctezuma received several omens and premonitions of impending disaster, including a fiery object in the sky, a spontaneous fire in a temple, a water spout in Lake Texcoco, and the sound of a woman wailing. These signs and omens were seen as foretellings of the Aztec's destruction.
Furthermore, the Spanish played a role in the Aztec's demise. In 1521, smallpox, brought by the Spanish, struck Tenochtitlan. The disease spread rapidly among the Aztec population and left them weak, unable to cultivate food, and starving. The Spanish took advantage of the Aztec's weakened state and eventually defeated them, converting many Aztecs to Christianity and renaming Tenochtitlan as Mexico City.
Overall, the natural disasters and the introduction of diseases by the Spanish were significant factors in the downfall of the Aztec civilization under Moctezuma.