What lead to the downfall of Assyria?

Answer 1

The Assyrian Army was constantly fighting. It usually won! In the process of constantly fighting battles, it continually lost good solders. The army wore down.

In addition, it did not have an effective way of subjecting its empire. The captured peoples became under Assyrian rule. Some of the richer native people moved away. Strangers moved into the area. Other that that, the people were a conquered people. They owed no allegiance to Assyria. Given the chance, they would join a rebellion.

Nebuchadnezzar became the king of Babylon. He attacked and captured a few Assyrian towns. Then he met two armies. He destroyed them. With the Assyrian army destroyed, Nebuchadnezzar captured the rest of the Assyrian Empire.

So Assyria fell through misgovernment of its conquered territories and constant warfare.