A universally accepted chronology for the entire ancient Near East remains to be established. On the basis of the Royal Canon of Ptolemy, a second-century A.D. astronomer, regnal dates can be determined with certainty in Babylonia only as far back as 747 B.C. (the accession of King Nabonassar). Through the use of excavated royal annals and chronicles, together with lists of annually appointed limmu-officials, the chronology of Assyria can be confidently extended back to 911 B.C. (the accession of King Adad-nirari II). The earliest certain link with Egypt is 664 B.C., the date of the Assyrian sack of the Egyptian capital at Thebes. Although it is often possible to locate earlier events quite precisely relative to each other, neither surviving contemporary documents nor scientific dating methods such as carbon 14, dendrochronology, thermoluminescence, and archaeoastronomy are able to provide the required accuracy to fix these events absolutely in time. The West Asian portion of the Timeline therefore employs the common practice of using, without prejudice, the so-called Middle Chronology, where events are dated relative to the reign of King Hammurabi of Babylon, which is defined as being ca. 1792–1750 B.C.
By 8000 B.C., agricultural communities are already established in northern Mesopotamia, the eastern end of the Fertile Crescent. Early in the sixth millennium B.C., farming communities, relying on irrigation rather than rainfall, settle ever further south along the Tigris and Euphrates rivers. As these new communities grow, monumental architecture and more elaborate forms of artistic representation reflect an increasingly differentiated social hierarchy. Forms of administration and recording are developed as cities emerge across the region, especially in the south. By 2500 B.C., cuneiform inscriptions describe rivalry between city-states, with rulers building temples and palaces decorated with royal imagery proclaiming their power. Within two centuries, the city-states of Mesopotamia are unified by Sargon of Akkad, who creates the first empire.