Around 500 BC, the area that is now Iran was the center of the Achaemenid Empire. The Greek city states fought against the Persian armies led by Darius the Great and Xerxes. Then Alexander the Great took the country by fighting the Achaemenid dynasty of Persia. He ruled until he died,then the Greek Seleucids ruled until they were defeated by the Parthian Empire which later fought the Roman Empire.