The Persian Empire was a series of successive Iranian or Iraniate empires that ruled over the Iranian plateau, the original Persian homeland, and beyond in Western Asia, South Asia, Central Asia and the Caucasus. The first Persian Empire formed under the Median Empire (728 BC-559 BC) after defeating and ending the Assyrian Empire with the help of Babylonians.
Achaemenid Persian Empire (550–330 BC) was the largest empire of the ancient world and the most widespread entity of it was under Darius the Great(Persian:) and Xerxes (or Xerkes)(Persian:) — famous in antiquity as the foe of the classical Greek states (See Greco-Persian Wars) — a united Persian kingdom that originated in the region now known as Pars province (Fars province) of Iran.
It was formed under Cyrus the Great, who took over the empire of the Medes, and conquered much of the Middle East, including the territories of the Babylonians, Assyrians, the Phoenicians, and the Lydians. Cambyses, Son of Cyrus the Great, continued his conquests by conquering Egypt. The Achaemenid Persian Empire was ended during the Wars of Alexander the Great, but Persian Empire arose again under the Parthian and Sassanid Empires of Iran, followed by Iranian post-Islamic Empires like Safavids, up to the modern day Iran.
Most of the successive states in Greater Iran prior to March 1935 are collectively called the Persian Empire by Western historians.
There are records of numerous ancient civilizations on the Iranian plateau before the arrival of Iranian tribes from Central Asia during the Early Iron Age. One of the main civilizations of Iran was the Elam to the east of Mesopotamia, which started from around 3000 BC.The recently discovered Jiroft Civilization occupied southeastern Iran and is claimed to have existed as far back as 3000 BC According to available written records, it is known to have existed beginning from around 3200 BC — making it among the world's oldest historical civilizations — and to have endured up until 539 BC. The Early Bronze Age saw the rise of urbanization into organized city states and the invention of writing (the Uruk period) in the Near East.
As early as the 10th and 9th century BC Aryan tribes (ancestors of Modern Iranians) speaking Indo-Iranian languages arrived on the Iranian plateau from Eastern Ukraine and Southern Russia. The arrival of Iranians on the Iranian plateau forced the Elamites to relinquish one area of their empire after another and to take refuge in Susiana, Khuzistan and nearby area, which only then became coterminous with Elam. The Proto-Iranians are traced to the Bactria-Margiana Archaeological Complex, a Bronze Age culture of Central Asia. By the 1st millennium BC, Medes, Persians, Bactrians and Parthians populated the Iranian plateau, while others such as the Scythians, Sarmatians, Cimmerians and Alans populated the steppes north of the Black Sea. The Saka and Scythian tribes remained mainly in the south and spread as far west as the Balkans and as far east as Xinjiang.
 Median and Achaemenid Empire (650 BC–248 BC)
Main articles: Median Empire and Achaemenid Empire
Persian Archers at Darius' palace at Susa
In 646 BC The Assyrian king Ashurbanipal sacked Susa, which ended Elamite supremacy in the region. For over 150 years Assyrian kings of nearby Northern Mesopotamia were seeking to conquer Median tribes of Western Iran. Under pressure from the Assyrian empire, the small kingdoms of the western Iranian plateau coalesced into increasingly larger and more centralized states. In the second half of the 7th century BC, the Median tribes gained their independence and were united by Deioces. In 612 BC Cyaxares, Deioces' grandson, and the Babylonian king Nabopolassar invaded Assyria and laid siege to and eventually destroyed Nineveh, the Assyrian capital, which led to the fall of theNeo-Assyrian Empire. The Medes are credited with the foundation of Iran as a nation and empire, and established the first Iranian empire, the largest of its day until Cyrus the Great established a unified empire of the Medes and Persians leading to the Achaemenian Empire (648–330 BC).
After his father's death in 559 BC, Cyrus the Great became king of Anshan but like his predecessors, Cyrus had to recognize Mede overlordship. In 552 BC Cyrus led his armies against the Medes and captured Ecbatana in 549 BC, effectively conquering the Median Empire and also inheriting Assyria. Cyrus later conquered Lydia and Babylon. Cyrus the Great created the Cyrus Cylinder, considered to be the first declaration of human rights and was the first king whose name has the suffix "Great". After Cyrus' death, his son Cambyses ruled for seven years (531-522 BC) and continued his father's work of conquest, making significant gains in Egypt. A power struggle followed Cambyses' death and, despite his tenuous connection to the royal line, Darius was declared king (ruled 522-486 BC). He was to be arguably the greatest of the ancient Persian rulers.
Representation palace of Darius at Persepolis
Darius' first capital was at Susa, and he started the building programme at Persepolis. He built a canal between the Nile and the Red Sea, a forerunner of the modern Suez Canal. He improved the extensive road system, and it is during his reign that mention is first made of the Royal Road (shown on map), a great highway stretching all the way from Susa to Sardis with posting stations at regular intervals. Major reforms took place under Darius. Coinage, in the form of the daric (gold coin) and the shekel (silver coin) was introduced (coinage had already been invented over a century before in Lydia ca. 660 BCE), and administrative efficiency was increased. The Old Persian language appears in royal inscriptions, written in a specially adapted version of cuneiform. Under Cyrus the Great and Darius the Great, the Persian Empire eventually became the largest empire in human history up until that point, ruling and administrating over most of the then known world. Their greatest achievement was the empire itself. The Persian Empire represented the world's first superpower.  that was based on a model of tolerance and respect for other cultures and religions. In 499 BC Athens lent support to a revolt in Miletus which resulted in the sacking of Sardis. This led to an Achaemenid campaign against Greece known as the Greco-Persian Wars which lasted the first half of the 5th century BC. During the Greco-Persian wars Persia made some major advantages and razed Athens in 480 BC, But after a string of Greek victories the Persians were forced to withdraw. Fighting ended with the peace of Callias in 449 BC. In 404 BC following the death of Darius II Egypt rebelled under Amyrtaeus. Later Egyptian Pharaohs successfully resisted Persian attempts to reconquer Egypt until 343 BC when Egypt was reconquered by Artaxerxes III.
 The Hellenic conquest
In 334 BC-331 BC Alexander the Great, also known in the Zoroastrian Arda Wiraz Nâmag as "the accursed Alexander", defeated Darius III in the battles of Granicus, Issus and Gaugamela, swiftly conquering the Persian Empire by 331 BCE. Alexander's empire broke up shortly after his death, and Alexander's general, Seleucus I Nicator, tried to take control of Persia, Mesopotamia, and later Syria and Asia Minor. His ruling family is known as the Seleucid Dynasty. However he was killed in 281 BC by Ptolemy Keraunos. Greek language, philosophy, and art came with the colonists. During the Seleucid Dynasty throughout Alexander's former empire, Greek became the common tongue of diplomacy and literature. Overland trade brought about some fascinating cultural exchanges. Buddhism came in from India, while Zoroastrianism travelled west to influence Judaism. Incredible statues of the Buddha in classical Greek styles have been found in Persia and Afghanistan, illustrating the mix of cultures that occurred around this time (See Greco-Buddhism).
 Parthian Empire (248 BC – 224 AD)
Main article: Parthian Empire
Bronze Statue of General Surena, National Museum of Iran.
A bust from The National Museum of Iran of Queen Musa, wife of Phraates IV of Parthia.
Parthia was led by the Arsacid dynasty, who reunited and ruled over the Iranian plateau, after defeating the Greek Seleucid Empire, beginning in the late 3rd century BC, and intermittently controlled Mesopotamia between ca 150 BC and 224 AD. It was the second native dynasty of ancient Iran (Persia). Parthia was the arch-enemy of the Roman Empire in the east; and it limited Rome's expansion beyond Cappadocia (central Anatolia). The Parthian armies included two types of cavalry: the heavily-armed and armoured cataphracts and lightly armed but highly-mobile mounted archers. For the Romans, who relied on heavy infantry, the Parthians were too hard to defeat, as both types of cavalry were much faster and more mobile than foot soldiers. On the other hand, the Parthians found it difficult to occupy conquered areas as they were unskilled in siege warfare. Because of these weaknesses, neither the Romans nor the Parthians were able to completely annex each other.
The Parthian empire lasted five centuries, longer than most Eastern Empires. The end of this long lasted empire came in 224 AD, when the empire was loosely organized and the last king was defeated by one of the empire's vassals, the Persians of the Sassanian dynasty.
 Sassanian Empire (224 – 651 AD)
Main article: Sassanian Empire
The first Shah of the Sassanian Empire, Ardashir I, started reforming the country both economically and militarily. The empire's territory encompassed all of today's Iran, Iraq, Armenia, Afghanistan, eastern parts of Turkey, and parts of Syria, Pakistan, Caucasia, Central Asia and Arabia. During Khosrau II's rule in 590-628, Egypt, Jordan, Palestine and Lebanon were also annexed to the Empire. The Sassanians called their empire Erânshahr (or Iranshahr, "Dominion of the Aryans", i.e. of Iranians).
The Sassanian Empire at its greatest extent.
Rock-face relief at Naqsh-e Rustam of Iranian emperor Shapur I (on horseback) capturing Roman emperor Valerian I (kneeing) and Philip the Arab (standing)
A chapter of Iran's history followed after roughly six hundred years of conflict with the Roman Empire. During this time, the Sassanian and Romano-Byzantine armies clashed for influence in Mesopotamia, Armenia and the Levant. Under Justinian I, the war came to an uneasy peace with payment of tribute to the Sassanians. However the Sassanians used the deposition of the Byzantine Emperor Maurice as a casus belli to attack the Empire. After many gains, the Sassanians were defeated at Issus, Constantinople and finally Nineveh, resulting in peace. With the conclusion of the Roman-Persian wars, the war-exhausted Persians lost the Battle of al-Qâdisiyah (632) in Hilla, (present day Iraq) to the invading forces of Islam. The Persian general Rostam Farrokhzad had been criticised for his decision to face the Arabs on their own ground, suggesting that the Persians could have prevailed if they had stayed on the opposite bank of the Euphrates. The first day of battle ended with Persian advances and the Arab force appeared as though it would succumb to the much larger Sassanian army. In particular, the latter's elephants terrified the Arab cavalry. By the third day of battle, Arab veterans arrived on the scene and reinforced the Arab army. In addition a clever trick whereby the Arab horses were decorated in costume succeeded in frightening the Persian elephants. When an Arab warrior succeeded in slaying the lead elephant, the rest fled into the rear, trampling numerous Persian fighters. At dawn of the fourth day, a sandstorm broke out blowing sand in the Persian army's faces resulting in total disarray for the Sassanian army and paving way for the Islamic conquest of Persia.
The Sassanian era, encompassing the length of the Late Antiquity period, is considered to be one of the most important and influential historical periods in Iran, and had a major impact on the world. In many ways the Sassanian period witnessed the highest achievement of Persian civilization, and constituted the last great Iranian Empire before the adoption of Islam. Persia influenced Roman civilization considerably during Sassanian times, their cultural influence extending far beyond the empire's territorial borders, reaching as far as Western Europe, Africa, China and India and also playing a prominent role in the formation of both European and Asiatic medieval art. This influence carried forward to the Islamic world. The dynasty's unique and aristocratic culture transformed the Islamic conquest and destruction of Iran into a Persian Renaissance. Much of what later became known as Islamic culture, architecture, writing and other contributions to civilization, were taken from the Sassanian Persians into the broader Muslim world.[35