The bronze age
The first cities started developing in southern Mesopotamia during the 4th millennium BC. With these ties of religion began to replace ties of kinship as the basis for society. Each city had a patron god, worshipped in a massive central temple called a ziggurat, and was ruled by a priest-king (ishakku). Society became more segmented and specialized and capable of coordinated projects like irrigation and warfare.
Along with cities came a number of advances in technology. By around 3000 BC, writing, the wheel, and other such innovations had been introduced. By now the SumerianPeoples of south Mesopotamia were all organized into a variety of independent City-States, such as Ur and Uruk, which by around 2500 BC had begun to coalesce into larger political units. By accomodating the conquered people's gods, religion became more polytheistic and government became somewhat more secular; the title of lugal, big man, appears along side the earlier religious titles, although his primary duty is still the worship of the state gods.
This process came to its natural conclusion with the development of the first empires around 2350 BC. A people called the Akkadians invaded the valley under Sargon I and established their supremacy over the Sumerians. They were followed by the empires of Ur (2200-2000) and the Old Kingdom of Babylonia (1800-1600).
Parallel developments were meanwhile occuring in Egypt, which by 3100 BC had been unified to form the Old Kingdom, and amongst the peoples of the Indus Valley in north-western India. All of these civilizations lie in fertile river valleys where agriculture is relatively easy once dams and irrigation are constructed to control the flood waters.
This started to change around the end of the third millennium as cities started to spread to the nearby hilly country: among the Assyrians in north Mesopotamia, the Canaanites in Syria-Palestine, to the Minoans in Crete, and to the Hittites in eastern Anatolia. Around this same time various immigrants, such as the Hittites and Achaeans, started appearing around the peripheries of civilization.
These groups are associated with the appearance of the light two-wheeled war chariot and typically with IndoEuropean languages. Horses and chariots require a lot of time and upkeep, so their use was mainly confined to a small nobility. These are the "heroic" societies familiar to us from epics like the Iliad and the Ramayana.
By around 1700-1500 most of the older centres had been overrun. Babylonia was conquered by the Kassites and the civilization of the Indus Valley was annihilated by the Indo-Aryans. Their kin, the Mitanni, subjugated Assyria and for a time menaced the Hittite kingdom, but were defeated by the two around 1350. Various Achaean kingdoms developed in Greece, most notably that of Mycenae, and by 1400 were dominant over the older Minoan cities. And the semitic Hyskos used the new technologies to occupy Egypt, but were expelled, leaving the empire of the New Kingdom to develop in their wake.
In 1200 BC all of these powers suddently collapsed. Cities all around the eastern Meditteranean were sacked within a span of a few decades by assorted raiders. The Achaean kingdoms disappeared, and the Hittite empire was destroyed. Egypt repelled its attackers with only a major effort, and over the next century shrunk to its territorial core, its central authority permanently weakened. Only Assyria escaped significant damage.
The iron age
The destruction at the end of the bronze age left a number of tiny kingdoms and City-States behind. A few Hittite centres remained in northern Syria, along with some Canaanite (Phoenician) ports that escaped destruction and now developed into great commercial powers. Southern Palestine initially fell to the Philistines, but by 1000 had been conquered by the Hebrews. And most of the interior, as well as Babylonia, was overrun by Aramaeans.
In this dark period a number of technological innovations spread, most notably iron working and the alphabet, developed by the Canaanites around 1500 BC. Also around this time, the Hebrew religion developed into the first major Monotheism, Judaism, which is still practiced today.
During the 9th century the Assyrians began to reassert themselves against the incursions of the Aramaeans, and over the next few centuries developed into a powerful and well-organized empire. Their armies were among the first to employ cavalry, which took the place of chariots, and had a reputation for both prowess and brutality. At their height, the Assyrians dominated all of Syria-Palestine, Egypt, and Babylonia. However, the empire began to collapse toward the end of the 7th century, and was obliterated by an alliance between a resurgent New Kindom of Babylonia and the Iranian Medes.
The subsequent balance of power was short-lived, though. In 550 BC the Persians revolted against the Medes and gained control of their empire, and over the next few decades annexed to it the realms of Lydia in Anatolia, Babylonia, and Egypt, as well as consolidating their control over the Iranian plateau nearly as far as India. This vast kingdom was divided up into various satrapies and governed roughly according to the Assyrian model, but with a far lighter hand. Around this time Zoroastrianism became the predominant religion in Persia.
The classical empires
From 492-449 BC the Persians made a series of unsuccesful attempts to conquer Greece. The civilization that had developed there since the end of the bronze age was organized along entirely different lines than those of the Middle East, consisting of numerous small City-States fielding citizen militiae. Nonetheless they banded together and proved quite capable of dealing with the massive armies of their foe.
By the fourth century Persia had fallen into decline. The campaigns of Xenophon illustrated how very vulnerable it had become to attack by an army organized along Greek lines, but the Greek city-states had weakened each other irreparably through in-fighting. However, in 338 BC the rising power of Macedonia overcame Greece, and under Alexander the Great turned its attention eastward. Persia was conquered in little more than a decade.
Alexander did not live long enough to conciliate his realm, and in the half-century following his death (323) it was carved up by his feuding generals. The Antigonids established themselves in Macedonia, the Ptolemies in Egypt, and various small principalities appeared in northern Anatolia. The greater share of the east went to the descendents of Seleucus Nicator. This period saw great innovations in mathematics, science, architecture, and the like, and Greeks founded cities throughout the east, which grew to be the world's first major metropolises. Their culture did not, however, reach very far into the countryside.
The Seleucids adopted a pro-western stance that alienated both the powerful eastern satraps and the Greeks who had migrated to the east. During the second century BC the Greek culture lost ground there, and the empire began to break apart. The province of Bactria revolted, and Parthia was conquered by the semi-nomadic Parni. By 141 BC the Parthians had established themselves as an empire, after the Seleucid model, and had conquered all of Iran and Mesopotamia. The Seleucid kingdom continued to decline and its remaining provinces were annexed by the Roman Republic in 64 BC.
The Parthian nobility reacted against growing Roman influences around the turn of the millennium. Throughout the next century there was a strong expansion of national culture and a dissolution in central authority. In 114 AD Trajan temporarily occupied Mesopotamia, and with the end of Hadrian's 40-year peace the two powers were at almost constant hostilities. Mesopotamia was occupied again, but the Parthians recovered and pillaged the Roman provinces. Shortly thereafter, though, the province of Persia rose up in revolt, and defeated the last Parthian emperor in 224.
The new dynasty, the Sasanids, restored central authority. In this period Zoroastrianism developed into an organized religion with close ties to the new state. Various sects of Christianity also spread throughout Iran, and Manichaeism developed from the two religions; these were initially tolerated but later persecuted as the Romans followed the opposite route. Conflicts with Rome, and later the Byzantine Empire, continued intermittently.
The Byzantines reached their lowest point under Phocas, with the Sasanids occupying the whole of the eastern Meditteranean. In 610, though, Heraclius took the thrown and began a succesful counter-attack, expelling the Persians and invading Media and Assyria. Unable to stop his advance, Khosrows II was assassinated and the Sasanid empire fell into anarchy. Weakened by their quarrels, neither empire was prepared to deal with the onslaught of the Arabs, newly unified under the banners of Islam and anxious to expand their faith. By 650 they had conquered all of Persia, Syria, and Egypt.
For subsequent history see History of Islam.