Persia’s beginnings can be traced to around 1000 B.C., when a number of nomadic peoples, including the Persians and the Medes, drifted into today’s Iran from Central Asia. Both enjoyed organizational success until the Persians overcame and absorbed the Medes around 550 B.C.

Leading the Persians at that time was a keen military strategist known as Cyrus the Great, a member of the Achaemenid family. The family would go on to control the throne for several hundred years.

According to the Greek warrior Xenophon, Cyrus was a judicious leader, strict, fair, and ambitious. Between 558 and 529 B.C., he seized control of Lydia, Babylonia, and what is now Iran, stretching his empire from Egypt to India.

After Cyrus died in 529 B.C., the sprawling empire gained some cohesion. Darius I, another Achaemenid, united the many conquered cities and tribal groups into a single Persian nation during his reign from 522 to 486 B.C.

Darius adopted a unified coinage, thereby simplifying the widespread economy, and added Egypt and northwestern India to the empire, which now covered almost two million square miles (five million square kilometers).

Imperial Persia’s 20 provinces were ruled by satraps, or governors. To help control their vast territory, the Achaemenid rulers built the 1,600-mile (2,575-kilometer) Royal Road from the Aegean coast of western Anatolia to what is now western Iran. They also built numerous secondary roads. Word traveled quickly, thanks to a courier system of hard-riding messengers, who could change to rested horses at stations spaced out along the graded roads. The roads also helped to speed the military to trouble spots and aid the travels of merchants.

Cyrus and Darius ruled over a wide area so successfully partly because they were tolerant of local ways and other religions. The two rulers attempted to retain local legal systems, customs, and religions, so long as they did not threaten the regime.

Zoroastrianism, the Persian religion, sought no converts. After Babylon was annexed, for example, the Jews who had been exiled there were allowed to return to Jerusalem.

The Persian realm prospered for more than two centuries with no fewer than four capitals. Excavations at one of them, Persepolis, reveal evidence of great wealth, grand architecture, and extravagant works of silver and gold.

Additions to Persia’s vast holdings came to a halt when Darius’s attempts to invade Europe only partially succeeded. Although the Persians once destroyed Athens, they were never able to conquer Greece.

After struggling with the Greek city-states, the Achaemenid dynasty fell to Alexander the Great of Macedon in 330 B.C. After his death his generals divided the realm into three portions, which became the Seleucid, Parthian, and Sassanid Empires. Conflicts with Rome eventually brought down the Seleucids and Parthians. The Sassanids held on to their land between the Caspian Sea and the Persian Gulf until finally overcome by Islam in A.D. 651.