Many nations built empires: the Sumerians,
the Akkadians, the Egyptians, the Babylonians, the Kassites, the Hittites, the
Assyrians, the Scythians, the Persians, the Macedonians, the Romans and others.
The benefit for the victor was that they could take goods and slaves from the
conquered nations, and make them pay taxes, so the conquerors grew rich. The
problem with building an empire was that it had to be ruled with an expensive
army to prevent rebellions, and civil servants had to collect the taxes and
enforce the laws.