There are many similiarities between the ancient Persian empire and that of the ancient Romans. First, both empires grew up in the same general area; that being around the Mediterranean Sea. They both had dealing with many of the same cultures: Greeks, Egyptians, etc. They both conquered through the use of a massive military force... the largest anyone had seen for their respective time periods. Both had very structured command centers for their military. Both empires conquered the "known world" in their time (relative term; but speaks to their effective military prowness).