Cyrus the Great (reigned 550-530 B.C.) was the founder of the Persian Empire. His reign witnessed the first serious contacts between Persians and Greeks and the permanent loss of political power by the peoples of the old centers of power in Mesopotamia.
In the new Median Empire, which shared with Babylon the spoils of the fallen Assyrian power, the Persians were a subordinate group, though closely related to the Medes and speaking a similar Indo-European language. They were ruled by their own local kings, and one of these married a daughter of the Median king Astyages; their son was Cyrus. Astyages seems not to have been popular, and when, in 550 B.C., Cyrus revolted, Astyages's own troops went over to Cyrus. The Median Empire thus became the Persian Empire. It is worth noting that Cyrus treated his defeated grandfather with honor and that instead of sacking Ecbatana, the Median capital, he kept it as one of his own because Pasargadae, the Persian center, was too remote for use as a capital. Cyrus also continued to keep Medes in high office.
The Medes and the Persians were so similar that foreigners tended to see only a change of dynasty (the Greeks still called the whole group Medes), but any such upset implied to the other powers a tempting weakness, and Cyrus soon found himself embroiled in new wars. The first was with Croesus, King of Lydia, a wealthy state in western Asia Minor whose subjects included the Greek cities along its coast. Croesus tried to find allies, including, with the aid of the Delphic oracle, the states of mainland Greece. But Cyrus moved too quickly. In a winter campaign he surprised and took Croesus's "impregnable" capital of Sardis. The Greek Herodotus says that Cyrus spared Croesus, though this has been questioned; Croesus may have committed suicide to avoid capture.
Cyrus then returned to the east, but he left Harpagus, a Mede, to complete the conquest. Over the next years Harpagus subdued the local peoples, including the Greek cities of the coast. The importance of this first serious contact between Greeks and Persians was doubtless unrecognized by either people, yet each was to become and remain for 2 centuries the main foreign preoccupation of the other.
Nabonidus (Nabu-Naid) of Babylon had originally favored Cyrus, but border conflicts led to war, and in 539 Cyrus captured Babylon. Here again his victory was made easy by the aid of Nabonidus's own subjects, for Nabonidus had alienated many powerful interests, especially the priest-hood of Marduk, Babylon's chief god. Cyrus posed as both a liberator and a supporter of the local gods and once in power pursued a careful policy of religious toleration. The most important example of this was his allowing the Jews to return to their homeland.
Not only the civilized states to the west but also the steppe peoples to the east engaged Cyrus's attention, and during his remaining years he pushed his frontiers to the Indus and the Jaxartes (modern Syr Darya). He died in 530 somewhere east of the Caspian Sea, fighting a tribe called the Massagetae.
Cyrus's right to be called "the Great" can hardly be questioned, and not only because his conquests were vastly larger than any before him anywhere on earth. The sudden emergence of Persia as the dominant power in the Near East is the most striking political fact of the 6th century B.C., while the conquest of Mesopotamia (Egypt was left for Cyrus's son Cambyses) marks the first time that a true Indo-European-speaking people had gained control of the old centers of civilization. Further, Cyrus's policy of generosity toward the conquered became standard Persian practice; among the imperial peoples of history, the Persians remain outstanding in their ready toleration of local customs and religions.
Though business and government documents from the Persian Empire are extant, knowledge of the personal lives of the Persian kings comes almost entirely from Greek sources. Herodotus's Histories ranks first; Xenophon's Cyropedia is mainly a propaganda piece. Good recent treatments are in A. T. Olmstead, History of the Persian Empire, Achaemenid Period (1948); Roman Ghirshman, Iran: From the Earliest Times to the Islamic Conquest (1954); and Richard N. Frye, The Heritage of Persia (1962). □