The first cause of the decline of Byzantine Empire was the Arab wars. In the west side of Byzantium conflicts rose and began to cause trouble for the Empire.
Answer:
Disease. When the Spanish arrived, they brought with them smallpox. Smallpox spread among the indigenous people and crippled their ability to resist the Spanish. The disease devastated the Aztec people, greatly reducing their population and killing an estimated half of Tenochtitlan's inhabitants.
Explanation:
hope this helps