Final answer:
Nubian armies were forced to retreat from Egypt due to dynastic conflicts, poor relations with Egyptian rulers, and the conquest of Egypt by the Neo-Assyrian Empire.
Step-by-step explanation:
The Nubian armies were forced to retreat from Egypt due to various factors. First, there were dynastic conflicts and poor relations with the rulers of Egypt. Additionally, the rise of the Funj kingdom in the south posed a threat to the Nubian kingdoms. Finally, the Neo-Assyrian Empire's conquest of Egypt brought an end to Nubian rule in Egypt.