The Persian Empire was founded by Cyrus the Great in 559 B.C. when he defeated the Median kdm in Iran and king Croesus of Lydia. He proceeded to unite the entire Middle East under his rule.
Under king Darius I the Persian Empire became the greatest empire the world had ever seen. It included Persia, Babylonia, Assyria, Media, Egypt and parts of India. Great arterial roads held the empire together. Imperial messengers were speeding along royal roads on horses, which by then had replaced slower camels hitherto used in desert lands. The Imperial authority was supported by the professional superiority of the royal bodyguard, the famous '10 000 immortals'.
Although most of the known western world respected the Imperial power the Scythian horsemen from the northern steppe regularly raided the border areas. Darius invaded Europe across the Bosphorus to attack the Scythians from the rear but was forced into retreat.
The suppression of a revolt in Ionia led to warfare with
Greece. After the Greek campaigns Persia had to deal with
rebellions in Egypt, Syria and Media and in 330 B.C. the mighty world
empire was conquered by
Alexander the Great.