The Achaemenid Empire (Old Persian Parsa) (c. 550–330 BCE), sometimes known as First Persian Empire, was founded in the 6th century BCE by Cyrus the Great who overthrew the Median confederation. It expanded to eventually rule over significant portions of the ancient world which at around 500 BCE stretched from the Indus Valley in the east, to Thrace and Macedon on the northeastern border of Greece making it the biggest empire the world had yet seen. The Achaemenid Empire would eventually control Egypt as well. It was ruled by a series of monarchs who unified its disparate tribes and nationalities by constructing a complex network of roads.
Calling themselves the Parsa after their original Aryan tribal name Parsua, Persians settled in a land which they named Parsua, bounded on the west by the Tigris River and on the south by the Persian Gulf. This became their heartland for the duration of the Achaemenid Empire. It was from this region that eventually Cyrus the Great (Cyrus II of Persia) would advance to defeat the Median, the Lydian, and the Babylonian Empires, opening the way for subsequent conquests into Egypt and Asia minor.
At the height of its power after the conquest of Egypt, the empire encompassed approximately 8 million km2 spanning three continents: Asia, Africa and Europe. At its greatest extent, the empire included the modern territories of Iran, Turkey, parts of Central Asia, Pakistan, Thrace and Macedonia, much of the Black Sea coastal regions, Afghanistan, Iraq, northern Saudi Arabia, Jordan, Israel, Lebanon, Syria, and all significant population centers of ancient Egypt as far west as Libya. It is noted in Western history as the antagonist foe of the Greek city states during the Greco-Persian Wars, for emancipation of slaves including the Jewish people from their Babylonian captivity, and for instituting infrastructures such as a postal system, road systems, and the usage of an official language throughout its territories. The empire had a centralised, bureaucratic administration under the Emperor and a large professional army and civil services, inspiring similar developments in later empires.
