The World of the Ancient Persians - Warfare
The Greco-Persian Wars (also often called the Persian Wars), were a series of conflicts between the Persian Empire and city-states of the Hellenic world that started in 499 BC and lasted until 450 BC. The collision between the fractious political world of the Greeks, and the enormous empire of the Persians began when Cyrus the Great conquered Ionia in ca. 550 BC. Struggling to rule the independently-minded cities of Ionia, the Persians appointed tyrants to rule each of them. This would prove the source of much trouble for both Greek and Persian alike.
In 499 BC, the then-tyrant of Miletus, Aristagoras, embarked on an expedition to conquer the island of Naxos, with Persian support. The expedition was a debacle, and pre-empting his dismissal, Aristagoras instead incited (with little difficulty) the whole of Hellenic Asia Minor into rebellion against the Persians. This was the beginning of the Ionian Revolt, which would last until 493 BC, progressively drawing more regions of Asia Minor into the conflict. Aristagoras secured military support from Athens and Eretria, and in 498 BC, these forces helped in the capture and burning of the Persian regional capital of Sardis. The Persian king Darius the Great vowed to have revenge on Athens and Eretria for this act. The revolt continued, with the two sides effectively stalemated throughout 497–495 BC. In 494 BC, the Persians regrouped, and attacked the epicentre of the revolt in Miletus. At the Battle of Lade, the Ionians suffered a decisive defeat, and the rebellion collapsed, the final embers being stamped out by the following year.
Seeking to secure his empire from further revolts, and from the interference of the mainland Greeks, Darius embarked on a scheme to pacify Greece, and to punish Athens and Eretria for the burning of Sardis. The first Persian invasion of Greece began in 492 BC, with the Persian general Mardonius subjugating Thrace and Macedon before several mishaps forced an early end to the campaign. In 490 BC a second force was sent to Greece, this time across the Aegean, under the command of Datis and Artaphernes. This expedition subjugated the Cyclades, before besieging, capturing and razing Eretria. However, whilst en route to attack Athens, the Persian force was decisively defeated by the Athenians at the Battle of Marathon, ending the Persian efforts for the time being. Darius therefore began to plan for the complete conquest of Greece, but died in 486 BC, responsibility for the conquest passing to his son Xerxes I. In 480 BC, Xerxes personally led the second Persian invasion of Greece, accompanied by a legendarily enormous army. Victory over the Allied Greek states (led by Sparta and Athens) at the famous Battle of Thermopylae allowed the Persians to overrun most of Greece, but seeking to destroy the Allied fleet, the Persians suffered a severe defeat at the Battle of Salamis. The following year, the Allies went on the offensive, defeating the Persian army at the Battle of Plataea, and thereby ending the invasion of Greece.
The Allies followed up their success by destroying the rest of the Persian fleet at the Battle of Mycale, before expelling Persian garrisons from Sestos (479 BC) and Byzantium (478 BC). The actions of the general Pausanias at the siege of Byzantium alienated many of the Greek states from the Spartans, and the anti-Persian alliance was therefore reconstituted around Athenian leadership, as the so-called Delian League. The Delian League continued to campaign against Persia for the next three decades, beginning with the expulsion of the remaining Persian garrisons from Europe. At the Battle of the Eurymedon in 466 BC the League won a double victory which finally secured freedom for the cities of Ionia. However, the involvement of the League in supporting an Egyptian revolt (from 460–454 BC) resulted in a catastrophic defeat and a suspension of campaigning. A fleet was despatched to Cyprus in 451 BC, but achieved little, and when it withdrew, the Greco-Persian Wars drew to a quiet end. Some historical sources suggest that the end of hostilities was marked by a peace treaty between Athens and Persia, the so-called Peace of Callias.
The Roman–Persian Wars were a series of conflicts between the Greco-Roman world and two successive Iranian empires. Contact between Parthia and the Roman Republic began in 92 BC; wars began under the late Republic, and continued through the Roman and Sassanid empires. They were brought to an end by the Arab Muslim invasions, which struck both empires with shattering effect shortly after the end of the last war between them.
Although warfare between the Romans and the Iranians lasted for seven centuries, the frontier remained largely stable. A game of tug of war ensued: towns, fortifications, and provinces were continuously sacked, captured, destroyed, and changing sides frequently. Neither side had the logistical strength or manpower to maintain such lengthy campaigns so far from their borders, and thus neither could advance too far without risking stretching their frontiers too thin. Both sides did make conquests beyond the border, but the balance was almost always restored in time. The line of stalemate shifted in the second century AD: it had run along the northern Euphrates; the new line ran east, or later northeast, across Mesopotamia to the northern Tigris. There were also several substantial shifts further north, in Armenia and the Caucasus.
The resources expended during the Roman–Persian Wars ultimately proved catastrophic for both empires. The prolonged and escalating warfare of the sixth and seventh centuries left them exhausted and vulnerable in the face of the sudden emergence and expansion of the Caliphate, whose forces invaded both empires only a few years after the end of the last Roman–Persian war. Benefiting from their weakened condition, the Arab Muslim armies swiftly conquered the entire Sassanid Empire, and deprived the Eastern Roman Empire of its territories in the Middle East, the Caucasus, Egypt, and the rest of North Africa. (Over the following centuries, most of the Byzantine empire came under Muslim rule.)
Conquest of Persia by Muslims
The explosive growth of the Arab Caliphate coincided with the chaos caused by the defeat of Sassanids in wars with the Byzantine Empire. Most of the country was conquered between 643 and 650 with the Battle of Nihawand marking the total collapse of the Sassanids. Arabs defeated Persians and other Iranians and introduced their religion.
Yazdgerd III, the last Sassanid emperor, died ten years after he lost his empire to the newly-formed Muslim Caliphate. He tried to recover some of what he lost with the help of the Turks, but they were easily defeated by Muslim armies. Then he sought the aid of the Chinese Tang dynasty. However, the Chinese never intervened on behalf of the Sassanids and instead, appointed Peroz, son of Yazdgerd as the governor over his own territory which the Tang named the "protectorate of Persia". This territory was overrun by the Arabs around the early 660s and Peroz escaped to the Tang court. The Umayyads would rule Persia for a hundred years. The Arab conquest dramatically changed life in Persia. Arabic became the new lingua franca, Islam eventually replaced Zoroastrianism, and mosques were built.
In 750 the Umayyads were ousted from power by the Abbasid dynasty. By that time, Persians had come to play an important role in the bureaucracy of the empire. The caliph Al-Ma'mun, whose mother was Persian, moved his capital away from Arab lands into Merv in eastern Iran.