The Persians were led during the seventh century BCE by Hakamanish (Achaemenes, in Greek), ancestor of the Achaemenian dynasty.

A descendant, Cyrus II (also known as Cyrus the Great or Cyrus the Elder), leads the combined forces of the Medes and the Persians to establish the most extensive empire known in the ancient world.

Cyrus defeats Croesus, the Lydian king of fabled wealth, by 546 BCE and secures control of the Aegean coast of Asia Minor, Armenia, and the Greek colonies along the Levant.

Moving east, he takes Parthia (land of the Arsacids, not to be confused with Parsa, which is to the southwest), Chorasmia (Khwarezm), and Bactria.

He besieges and captures Babylon in 539 BCE and releases the Judahites who had been held captive there, thus earning his immortalization in the Book of Isaiah.

When Cyrus dies in 529 BCE, his kingdom extends as far east as the Hindu Kush in present-day Afghanistan.

Cyrus's successors are less successful.

His unstable son, Cambyses II, conquers Egypt in 525 BCE but later commits suicide during a revolt led by a priest, Gaumata, who holds the throne until 522 BCE, when he is overthrown by a member of a lateral branch of the Achaemenian family, Darius I (also known as Darayarahush and Darius the Great).

Darius attacks the Greek mainland, which has supported rebellious Greek colonies under his aegis, but his defeat at the Battle of Marathon in 490 BCE forces him to retract the limits of the empire to Asia Minor.

The Achaemenians hereafter consolidated areas firmly under their control.

It is Cyrus and Darius who, by sound and farsighted administrative planning, brilliant military maneuvering, and a humanistic worldview, establish the greatness of the Achaemenians, raising them in less than thirty years from an obscure tribe to a world power.

The quality of the Achaemenians as rulers begins to disintegrate, however, after the death of Darius in 486 BCE.

His son and successor, Xerxes, chiefly occupies himself with suppressing revolts in Egypt and Babylonia.

He also attempts to conquer the Greek Peloponnesus, but, encouraged by a victory at Thermopylae, he overextends his forces and suffers overwhelming defeats at Salamis and Plataea.

Darius I revolutionizes the economy by placing it on a system of silver and gold coinage.

Trade is extensive, and under the Achaemenians an efficient infrastructure facilitates the exchange of commodities among the far reaches of the empire.

As a result of this commercial activity, Persian words for typical items of trade become prevalent throughout the Middle East and will eventually enter the English language; examples include asparagus, bazaar, lemon, melon, orange, peach, sash, shawl, spinach, tiara, and turquoise.

Trade is one of the empire's main sources of revenue, along with agriculture and tribute.

Other accomplishments of Darius's reign include  codification of the data, a universal legal system upon which much of later Iranian law will be based, and construction of a new capital at Persepolis, where vassal states offer their yearly tribute at the festival celebrating the spring equinox.

In its art and architecture, Persepolis reflects Darius's perception of himself as the leader of conglomerates of people to whom he has given a new, single identity.

The Achaemenian art and architecture found here is at once distinctive and highly eclectic.

The Achaemenians take the art forms and the cultural and religious traditions of many of the ancient Middle Eastern peoples and combine them into a single form.

This Achaemenian artistic style is evident in the iconography of Persepolis, which celebrates the king and the office of the monarch.

The most common language in the Achaemenid empire is Aramaic.

Old Persian is the "official language" but is used only for inscriptions and royal proclamations.

The Achaemenians are enlightened despots who allow a certain amount of regional autonomy in the form of the satrapy system.

A satrapy is an administrative unit, usually organized on a geographical basis.

A satrap (governor) administer the region, a general supervises military recruitment and ensures order, and a state secretary keeps official records.

The general and the state secretary report directly to the central government.

The twenty satrapies are linked by a twenty-five hundred-kilometer highway, the most impressive stretch being the royal road from Susa to Sardis built by command of Darius I.

Relays of mounted couriers can reach the most remote areas in fifteen days.

As if to remind the satrapies of their limited independence, royal inspectors, the "eyes and ears of the king,"  tour the empire and report on local conditions.

Inclinations toward restiveness are further discouraged by the existence of the king's personal bodyguard of ten thousand men, called the Immortals.

Darius successfully invades southern Russia in a campaign against the Scythians east of the Caspian Sea.

Darius invades the Balkans in 515 BCE but fails in his attack on the lower Danube tribes.

Cambyses II, Persia’s second Achaemenid king, either commits suicide or dies accidentally in Syria in the summer of 522 BCE while returning to Persia from Egypt, supposedly to deal with a revolt by a usurper claiming to be Cambyses’ younger brother Bardiya, called Smerdis by the Greeks. (The Greek historian Herodotus, writing a century later, will allege in his history that Cambyses was insane.)

Having supposedly taken the throne in March, Bardiya reigns for no more than eight months before being slain in September by Darius—a member of the late Cambyses’ royal bodyguard—and other Persian nobles suspicious of his origin.

Darius, the son of Hystaspes, the satrap of Parthia, ascends the Achaemenid throne, claiming that he is restoring the kingship to the rightful Achaemenid royal family, of which his is a collateral branch. (As Darius’ father and grandfather are alive at his accession, it is unlikely that he is next in line to the throne. According to Darius' account in his later trilingual inscription at Bisitun, Cambyses had secretly murdered Bardiya years before, and the usurping Bardiya was a successful impersonation by Gaumata the Magian. Certain modern scholars consider that Darius fabricated the story of Gaumata to justify his actions and that his murdered predecessor had indeed been a son of Cyrus.)

Cambyses’s conquest of Egypt has allowed the relatively benevolent Darius to rule a centralized empire from the Mediterranean to the Indus.

He divides the Achaemenid empire into satrapies for administrative convenience, organizes the postal system on the royal roads, institutes an efficient central bureaucracy, and strives to standardize legal practices throughout the empire with the imposition of Universal Law (the King’s Law).

He mints gold coins called “darics.”

Zoroastrianism spreads with Darius’s encouragement.

Darius, not generally recognized as Persia’s king, thus imposes his rule by force, fighting many spontaneous rebellions against his authority early in his reign, in such places as Susiana, …

…Babylonia, …

…Media, Sagartia, and Margiana, where independent governments had been erected.

Circumstances force him to also send troops to …