Final answer:
The decline of the Byzantine Empire was caused by the Arab invasions, political disunity among empires, religious beliefs, and military tactics.
Step-by-step explanation:
There were several causes for the decline of the Byzantine Empire. The first cause was the Arab invasions and the rapid spread of Islam through military conquest. The innovative military tactics of the Arab armies allowed them to outmaneuver and defeat their opponents. Additionally, political disunity among empires, specifically the division and internal conflicts within the Byzantine and Sassanian empires, contributed to the decline. Finally, religious beliefs played a role, as the fervent religious belief of the Arab armies motivated them to conquer new territories, resulting in the erasure of existing cultures.
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