The history of Iran, commonly also known as Persia in the Western world, is intertwined with the history of a larger region, also to an extent known as Greater Iran, comprising the area from Anatolia, the Bosphorus, and Egypt in the west to the borders of Ancient India and the Syr Darya in the east, and from the Caucasus and the Eurasian Steppe in the north to the Persian Gulf and the Gulf of Oman in the south.
Iran is home to one of the world's oldest continuous major civilizations, with historical and urban settlements dating back to 7000 BC. The southwestern and western part of the Iranian Plateau participated in the traditional Ancient Near East with Elam, from the Early Bronze Age, and later with various other peoples, such as the Kassites, Mannaeans, and Gutians. Georg Wilhelm Friedrich Hegel names the Persians as the first Historical People.The Medes unified Iran as a nation and empire in 625 BC. The Achaemenid Empire (550–330 BC), founded by Cyrus the Great, was the first of the Persian empires to rule from the Balkans to North Africa and also Central Asia, spanning three continents, from their seat of power in Persis (Persepolis). It was the largest empire yet seen and the first world empire. The First Persian Empire was the only civilization in all of history to connect over 40% of the global population, accounting for approximately 49.4 million of the world's 112.4 million people in around 480 BC. They were succeeded by the Seleucid, Parthian and Sasanian Empires, who successively governed Iran for almost 1000 years and made Iran once again as a leading power in the world. Persia's arch-rival was the Roman Empire and its successor, the Byzantine Empire.
The Persian Empire proper begins in the Iron Age, following the influx of Iranian peoples. Iranian people gave rise to the Medes, the Achaemenid, Parthian, and Sasanian Empires of classical antiquity.
Once a major empire, Iran has endured invasions too, by the Greeks, Arabs, Turks, and the Mongols. Iran has continually reasserted its national identity throughout the centuries and has developed as a distinct political and cultural entity.
The Muslim conquest of Persia (633–656) ended the Sasanian Empire and was a turning point in Iranian history. Islamization of Iran took place during the eighth to tenth centuries and led to the eventual decline of Zoroastrianism in Iran as well as many of its dependencies. However, the achievements of the previous Persian civilizations were not lost, but were to a great extent absorbed by the new Islamic polity and civilization.
Iran, with its long history of early cultures and empires, had suffered particularly hard during the late Middle Ages and the early modern period. Many invasions of nomadic tribes, whose leaders became rulers in this country, affected it negatively.
Iran was once again reunified as an independent state in 1501 by the Safavid dynasty, which converted Iran to Shia Islam as the official religion of their empire, marking one of the most important turning points in the history of Islam. Functioning again as a leading power, this time amongst the neighboring Ottoman Empire, their arch-rival for centuries, Iran had been a monarchy ruled by an emperor almost without interruption from 1501 until the 1979 Iranian Revolution, when Iran officially became an Islamic republic on April 1, 1979.
Over the course of the first half of the 19th century Iran lost many of its territories in the Caucasus, which were parts of Iran for centuries, comprising modern-day Eastern Georgia, Dagestan, Azerbaijan, and Armenia, to its rapidly expanding and emerged neighboring rival the Russian Empire, following the Russo-Persian Wars between 1804–13 and 1826–8.
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 Assyria, the small kingdoms of the western Iranian plateau coalesced into increasingly larger and more centralized states.
In the second half of the seventh century BC, the Medes 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 the Neo-Assyrian Empire. Urartu was later on conquered and dissolved as well by the Medes. 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 Achaemenid Empire (c.550–330 BC).
Cyrus the Great overthrew, in turn, the Median, Lydian, and Neo-Babylonian Empires, creating an empire far larger than Assyria. He was better able, through more benign policies, to reconcile his subjects to Persian rule; and the longevity of his empire was one result. The Persian king, like the Assyrian, was also "King of Kings", xšāyaθiya xšāyaθiyānām(shāhanshāh in modern Persian) – "great king," Megas Basileus, as known by the Greeks.
Cyrus's son, Cambyses II, conquered the last major power of the region, ancient Egypt, causing the collapse of the Twenty-sixth Dynasty of Egypt. Since he became ill and died before, or while, leaving Egypt, stories developed, as related by Herodotus, that he was struck down for impiety against the ancient Egyptian deities. The winner, Darius I, based his claim on membership in a collateral line of the Achaemenid Empire.
Darius' first capital was at Susa, and he started the building programme at Persepolis. He rebuilt 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 standardized (coinage had already been invented over a century before in Lydia c. 660 BC but not standardized), and administrative efficiency was increased.
The Old Persian language appears in royal inscriptions, written in a specially adapted version of the cuneiform script. Under Cyrus the Great and Darius I, 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, as well as spanning three continents, namely Europe, Asia, and Africa. 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