At its peak, the Persian Empire stretched across three continents and unified more of the civilized world under a single government than any empire before it. Cyrus the Great entered Babylon in 539 BC as a liberator. Darius the First built the Royal Road, standardized the gold coin, and divided the empire into provinces that Rome would later imitate.
The Greeks called it Persia. The people who lived there had always called it something else.
This brief traces the full arc: from the Achaemenid dynasty through Alexander’s conquest, to its birth as “Iran,” and its evolution toward an Islamic Republic.
