A pattern of unification and fragmentation
Mesopotamian political history is often described as a cycle. Powerful rulers unified large areas, the central state weakened, and regions broke away or were conquered from outside. The dates below are approximate, and the causes of collapse are often argued over, because the surviving sources tend to be royal inscriptions, administrative archives and later chronicles written with their own purposes.
City-states of the Early Dynastic period
In the third millennium BCE the south was divided among city-states, each centred on a walled city, its temples and the farmland around it. Ur, Uruk, Lagash, Umma and Kish were among the most prominent. Under Sumerian city-state kingship, a ruler might be called lugal (“big man”) or ensi, and was expected to maintain the temple of the city god and the canals that fed the fields.
These cities fought one another, often over boundaries and water. A long dispute between Lagash and Umma over border land is documented in inscriptions, and the Stele of the Vultures records a victory of Lagash. No city held permanent control, though some rulers claimed titles implying wider authority.
The Akkadian state
Around 2330 BCE Sargon, a ruler of the city of Akkad, defeated the cities of the south and created what is often called the first territorial empire in the region. He and his successors campaigned in several directions and appointed governors in conquered cities. The language of the dynasty, Akkadian, became a major written language.
The state weakened in the 2200s BCE. Revolts, succession troubles and pressure from highland peoples such as the Gutians are all mentioned. Some researchers have also pointed to a period of drought around that time, but how much it contributed is debated. The location of Akkad itself has not been securely identified.
The Third Dynasty of Ur
After a period of Gutian influence and local rulers, Ur-Nammu of Ur founded a new kingdom around 2100 BCE. Historians call it Ur III. It is known for large-scale record keeping: tens of thousands of tablets document labour, livestock, grain and textiles under a tightly managed bureaucracy. Ur-Nammu is also linked to the oldest surviving law collection.
Ur III ended around 2000 BCE. Sources point to a combination of food shortage, the loss of outlying provinces, pressure from Amorite groups, and an attack by Elam, in which Ur was sacked and its king Ibbi-Sin taken away. The relative weight of these causes is still discussed.
Old Babylonian states
In the centuries after Ur III, Amorite dynasties ruled several competing kingdoms, including Isin, Larsa, Mari, Assyria and Babylon. Under Hammurabi, who ruled for about four decades in the eighteenth century BCE, Babylon expanded to control much of southern and central Mesopotamia. His reputation rests partly on the laws of Hammurabi, though his kingdom was fragile and his successors lost territory.
Babylon was sacked by a Hittite army around 1595 BCE, according to the commonly used chronology, ending the dynasty. The Kassite dynasty then ruled Babylonia for roughly four centuries, a period of relative stability.
The Assyrian Empire
Assyria, centred on Ashur, Nineveh and nearby cities in the north, was a regional state for centuries. From the ninth century BCE the Neo-Assyrian kings expanded dramatically, reaching the Mediterranean and for a time Egypt. Their methods included a professional army, deportation of populations, tribute and a network of provincial governors. The Assyrian Empire left monumental art and a huge archive, including the library of Ashurbanipal.
The empire collapsed with surprising speed in the late seventh century BCE. Civil war between rival claimants, revolt in Babylonia and attack by Babylonians and Medes together are the usual explanation. Nineveh fell in 612 BCE.
The Neo-Babylonian state
Nabopolassar, who took the Babylonian throne in 626 BCE, led the revolt against Assyria. His son Nebuchadnezzar II (reigned 605 to 562 BCE) extended Babylonian control over Syria and the Levant and rebuilt Babylon on a grand scale. After his death the throne changed hands several times, and the Neo-Babylonian succession was unsettled before Nabonidus became king in 556 BCE.
In 539 BCE Cyrus of Persia took Babylon, ending native rule over Mesopotamia. Contemporary Babylonian texts suggest the city was not destroyed, and Cyrus presented himself as a legitimate ruler rather than a conqueror. Explanations for the fall include Babylonian internal tensions and Persian military strength, although the details are partly drawn from sources hostile to Nabonidus.
What the pattern shows
No single cause explains every collapse. Common themes include succession disputes, rebellion in provinces, pressure from neighbouring powers, and environmental stress. Political ideas, however, survived the states themselves: kingship as a duty to provide justice, administration through written records, and the use of Akkadian as a language of diplomacy all outlasted individual dynasties.