What explains the rise and fall of the Assyrians?

The Assyrian kingdom originated in northern Mesopotamia. The Assyrians built up the military and conquered many of their neighbors, including Babylonia, and took over much of Syria all the way to the Mediterranean. The Assyrians then moved into Anatolia, where the pressure they put on the Hittite Empire was one factor in its collapse. Assyria’s success allowed it to become the leading power in the Near East, with an army that at times numbered many tens of thousands.