How did the Assyrians and the Persians consolidate their power and control the subjects of their empires?

Small kingdoms like those of the Phoenicians and the Jews could exist only in the absence of a major power. In the ninth century B.C.E. one major power arose in the form of the Assyrians, who starting in northern Mesopotamia created an empire through often-brutal military conquests. And from a base in what is now southern Iran, the Persians established an even larger empire, developing effective institutions of government.