Though capitals and dynasties rose and fell, the land between the rivers remained captive to the annual floods and to the consequent need for cooperation, superlative engineering, and frequent redistribution of land. The Mesopotamians’ highest intellectual achievements were therefore practical rather than speculative. The development of writing is a prime example of their talents. The Mesopotamians were also the first great mathematicians. Using a numerical system based on sixty instead of the modern ten, they produced reference tables for multiplication, division, square roots, cube roots, and other functions. Their greatest achievement, however, was the place-value system of notation in which the value of each digit is determined by its position after the base instead of by a separate name. This makes describing large numbers possible and is the basis of all modern numeral systems. The Babylonians also created one of the first comprehensive legal codes. Named after Hammurabi, it is almost certainly a compendium of existing laws rather than new legislation and reflects a legal tradition that had been developing for centuries. Its basic principles were retribution in kind and the sanctity of contracts. In criminal cases this meant literally “an eye for an eye, a tooth for a tooth,” if the social status of the parties was equal. If not, a defendant of higher status could usually escape by paying a fine. Blood feuds, private retribution, and other features of tribal law were, however, forbidden. This same sense of retributive justice extended to the punishment of fraud and negligence. A builder whose house collapsed and killed its occupants could be executed; tavern keepers who watered their drinks were drowned. Craftsmen were required to replace poor workmanship at their own expense, and farmers who failed to keep their ditches and levees in good repair were sold into slavery if they could not compensate the victims of their carelessness. Contracts governed everything from marriage to interest rates and could not be broken without paying a heavy fine. Hammurabi’s Code was driven by an almost oppressive sense of social responsibility. The ecology of Mesopotamia was both fragile and highly artificial. Only elaborate regulation could prevent disaster, and the law is explicit on many aspects of trade, agriculture, and manufacturing. Courts and town councils took an interest in matters that other cultures have regarded as private. Furthermore, because there were no lawyers, the parties to a dispute were expected to plead their own cases. Marriage, as in most ancient cultures, was arranged by parents. The bride received a dowry, which she was entitled to keep in the event of widowhood or divorce. Husbands could demand a divorce at any time but had to pay maintenance and child support unless they could demonstrate that the wife had failed in her duties. These duties, like all other aspects of the marriage arrangement, were spelled out in a detailed contract that in effect made the couple a single person, responsible before the law for their actions and their debts. The latter was an important point, for husbands had the right to sell wives and children into servitude, usually for no more than two or three years, to satisfy their creditors. The system was patriarchal, but wives could sue for divorce on grounds of cruelty or neglect, or if their husband falsely accused them of adultery. If adultery were proved, the guilty couple would be tied together and drowned; if the aggrieved husband forgave his wife, her lover would be pardoned as well. All of these family issues were heard before the city councils, which demonstrates the continuing importance of local government even after the establishment of an empire. Women, like men, were expected to plead their own cases—a right often denied them in more modern legal systems—but recourse to the law had its perils. To reduce litigation, Hammurabi’s Code decreed the death penalty for those who brought false accusations or frivolous suits. 
Hammurabi, like most lawgivers, claimed divine sanction for his code, but Mesopotamian religion was not legalistic. The Sumerians had worshipped more than three thousand deities, most of whom represented natural forces or the spirit of a particular locality. In time many of them acquired human form, and a rich mythology developed around their adventures. Babylon made its city god, Marduk, its chief, while the Assyrians accorded similar honors to Ashur. Both were thought of as creators who had brought the universe out of primal chaos. Other gods and goddesses were still worshipped, but in an apparent step toward monotheism, they were increasingly described as agents of Marduk or Ashur and eventually as manifestations of a single god. The power of the gods was absolute. Humans were dependent on their whims and could hope only to propitiate them through the ceremonies of the priests.
The organization of Sumerian society was probably much like that of earlier Neolithic communities, and its political institutions reflect the ancient idea of chieftainship. More is known about it only because the Sumerians were the first Western people to create a written language. Their political and economic relationships had reached a level of complexity that required something more than the use of movable clay tokens to record transactions, a practice characteristic of many earlier cultures. Though the Sumerian language was apparently unrelated to any other and was used only for ritual purposes after the second millennium B.C., all later Mesopotamian cultures adopted its cuneiform system of writing.
Cuneiform refers to the wedge-shaped marks left by a stylus when it is pressed into a wet clay tablet. Sumeria was rich in mud, and slabs of clay were perfect for recording taxes, land transfers, and legal agreements. When the document was ready, the tablet could be baked hard and stored for future reference.
The Sumerians, Akkad, Babylonia, and Assyria
Even with written records, political relations between the Sumerian city-states are difficult to reconstruct. As populations increased, struggles over boundaries and trading rights grew more violent, and by 2300 B.C. inter-city conflicts engulfed all of Mesopotamia. At times, a king would claim to rule over more than one city or over Sumer as a whole. There may therefore have been no Sumerian Empire, or if there was, its existence could have been brief. According to his inscriptions, Lugalzaggeszi of Umma (c. 2375 B.C.) achieved control over the entire region only to have it taken from him by a non-Sumerian, Sargon of Akkad (reigned
c. 2350–2300 B.C.).
The Akkadian triumph marked the beginning of a new imperial age. The unification of southern and central Mesopotamia provided Sargon with the means to conquer the north together with Syria. Though Akkadian rule was brief, it transmitted elements of Mesopotamian culture throughout the Middle East, and Akkadian, a Semitic language, became standard throughout the Tigris and Euphrates valleys. But the brevity of Sargon’s triumph set a pattern for the political future. For a millennium and a half, the rulers of different regions in succession achieved hegemony over all or part of Mesopotamia. This was normally achieved by force combined with the careful manipulation of alliances and ended when the ruling dynasty fell prey either to the divisive forces that had created it or to invasions by people from the surrounding highlands. Throughout its history, Mesopotamia’s wealth and lack of natural defenses made it a tempting prize for conquerors.
After the overthrow of Sargon’s descendents by a desert people known as the Guti and a brief revival of Sumerian power under the Third Dynasty of Ur, Babylon became the chief political and cultural center of the region. Under Hammurabi (ruled c. 1792–1750 B.C.) the Babylonians achieved hegemony over all of Mesopotamia, but a series of invasions after 1600 B.C. led to a long period of political disorder. The invaders, the most important of whom were Hittites, an Indo-European people from central Asia Minor. Their influence was otherwise impermanent, but a rivalry soon developed between Babylon and Assyria, a kingdom in the northern part of the valley centered first on the city of Ashur and later on Nineveh.
The Assyrians, a fierce people who spoke a dialect of Akkadian, may have been the first people to coordinate the use of cavalry, infantry, and missile weapons. Not only were their armies well organized, but their grasp of logistics also appears to have surpassed that of other ancient empires. Though in other respects a highly civilized people whose literary and artistic achievements continued the traditions of Sumer and Babylon, they waged psychological warfare by cultivating a reputation for horrific cruelty. They eventually defeated the Babylonians and after 933 restored the achievements of Sargon by establishing an empire that stretched from Egypt to Persia. In spite of these violent political alterations, Mesopotamia remained culturally homogeneous for nearly three thousand years.
