It took more than a year (522–521 bc) of hard fighting to put down the revolts associated with Bardiya’s claim to the throne and Darius’s succession to power. Almost every province of the empire was involved in the conflict, including Persia and, most particularly, Media. A balanced policy of clemency backed by the swift and thorough punishment of any captured rebel leader, in combination with a well-coordinated and carefully timed distribution of loyal forces, eventually brought peace to the empire and undisputed power to Darius. He then turned his attention to the organization and consolidation of his inheritance, and it was for this role—that of lawgiver and organizer—that he himself, to judge from his inscriptions, most wished to be remembered.
Such activities, however, did not prevent Darius from following an active expansionist policy. Campaigns to the east confirmed gains probably made by Cyrus the Great and added large sections of the northern Indian subcontinent to the list of Persian-controlled provinces. Expansion in the west began about 516 bc when Darius moved against the Hellespont as a first step toward an attack on the Scythians along the western and northern shores of the Black Sea. The real strategic purpose behind this move probably was to disrupt and, if possible, interrupt Greek trade with the Black Sea area, which supplied much grain to Greece. Crossing into Europe for the first time, Darius campaigned with comparatively little success to the north of the Danube River. He retreated in good order, however, with only limited losses, and a bridgehead across the Hellespont was established.
Perhaps partly in response to these developments or perhaps for more purely internal reasons, the Ionian Greek cities on the west coast of Asia Minor revolted against Persian rule in 500 bc. The Persians were apparently taken by surprise, and at first the rebellion prospered. The Ionians received some limited assistance from the Athenians and in 498 felt strong enough to make another offensive. With one hand Darius negotiated; with the other he assembled a counterattack. The first Persian military efforts proved only partially successful, however, and the Ionians enjoyed another respite in the years 496–495. A renewed Persian offensive in 494 was successful. The Greek fleet was badly beaten off Miletus, and the Persian land army began a systematic reduction of the rebel cities. About 492 Mardonius, a son-in-law of Darius, was made special commissioner to Ionia. He suppressed local tyrants and returned democratic government to many cities. In time the wounds caused by the revolt and its suppression healed, and by 481 Xerxes was able to levy troops in this region with little trouble.
By 492 bc Mardonius had also recovered Persian Thrace and Macedonia, first gained in the campaign against the Scythians and lost during the Ionian revolt. There followed the Persian invasion of Greece that led to Darius’s defeat at the Battle of Marathon late in the summer of 490 bc. The great king was forced to retreat and to face the fact that the Greek problem, which had probably seemed to the Persians a minor issue on the western extremity of the empire, would require a more concerted and massive effort. Thus began preparations for an invasion of Greece on a grand, coordinated scale. These plans were interrupted in 486 by two events: a serious revolt in Egypt, and the death of Darius. Xerxes I
Xerxes (reigned 486–465 bc), Darius’s eldest son by Queen Atossa, was born after his father had come to the throne; he had been designated official heir perhaps as early as 498, and while crown prince he had ruled as the king’s governor in Babylon. The new king quickly suppressed the revolt in Egypt in a single campaign in 484. Xerxes then broke with the policy followed by Cyrus and Darius of ruling foreign lands with a fairly light hand, and, in a manner compatible with local traditions, he ruthlessly ignored Egyptian forms of rule and imposed his will on the rebellious province in a thoroughly Persian style. Plans for the invasion of Greece begun under Darius were then still further delayed by a major revolt in Babylonia about 482 bc, which also was suppressed with a heavy hand.
Xerxes then turned his attention westward to Greece. He wintered in Sardis in 481–480 and thence led a combined land and sea invasion of Greece. Northern Greece fell to the invaders in the summer of 480, the Greek stand at Thermopylae in August of 480 came to naught, and the Persian land forces marched on Athens, taking and burning the Acropolis. But the Persian fleet lost the Battle of Salamis, and the impetus of the invasion was blunted. Xerxes, who had by then been away from Asia rather long for a king with such widespread responsibilities, returned home and left Mardonius in charge of further operations. The real end of the invasion came with the Battle of Plataea, the fall of Thebes (a stronghold of pro-Persian forces), and the Persian naval loss at Mycale in 479. Of the three, the Persian loss at Plataea was perhaps the most decisive. Up until Mardonius was killed, the issue of the battle was probably still in doubt, but, once leaderless, the less organized and less disciplined Persian forces collapsed. Time and again in later years this was to be the pattern in such encounters, for the Persians never solved the military problem posed by the disciplined Greek hoplites.
The formation of the Delian League, the rise of Athenian imperialism, troubles on the west coast of Asia Minor, and the end of Persian military ambitions in the Aegean followed rapidly in the decade after Plataea. Xerxes probably lost interest in the proceedings and sank deeper and deeper into the comforts of life in his capital cities of Susa, Ecbatana, and Persepolis. Harem intrigues, which were steadily to sap the strength and vitality of the Achaemenian Empire, led to the king’s assassination in 465 bc. Artaxerxes I to Darius III
The death of Xerxes was a major turning point in Achaemenian history. Occasional flashes of vigour and intelligence by some of Xerxes’ successors were too infrequent to prevent eventual collapse but did allow the empire to die gradually. It is a tribute to Cyrus, Cambyses, and Darius that the empire they constructed was as resilient as it proved to be after Xerxes.
The three kings that followed Xerxes on the throne—Artaxerxes I (reigned 465–425 bc), Xerxes II (425–424), and Darius II Ochus (423–404)—were all comparatively weak as individuals and as kings, and such successes as the empire enjoyed during their reigns were mainly the result of the efforts of subordinates or of the troubles faced by their adversaries. Artaxerxes I faced several rebellions, the most important of which was that of Egypt in 459, not fully suppressed until 454. An advantageous peace (the Peace of Callias) with Athens was signed in 448 bc, whereby the Persians agreed to stay out of the Aegean and the Athenians agreed to leave Asia Minor to the Achaemenids. Athens broke the peace in 439 in an attack on Samos, and in its aftermath the Persians made some military gains in the west. Xerxes II ruled only about 45 days and was killed while in a drunken stupor by the son of one of his father’s concubines. The assassin was himself killed by Darius II, who rose to the throne through palace intrigue. Several revolts marred his reign, including one in Media, which was rather close to home.