Mesopotamia represents the earliest indications of large-scale warfare. Mesopotamian cities always had walls – some of which were 30 feet high and 60 feet wide, essentially enormous piles of earth strengthened by brick. The evidence (based on pictures and inscriptions) suggests, however, that most soldiers were peasant conscripts with little or no armor and light weapons. In these circumstances, defense almost always won out over offense, making the actual conquest of foreign cities very difficult if not impossible, and hence while cities were around for thousands of years (again, from about 3500 BCE), there were no empires yet. Cities warred on one another for territory, captives, and riches, but they rarely succeeded in conquering other cities outright. War was instead primarily about territorial raids and perhaps noble combats meant to demonstrate strength and power.
Over the course of the third millennium BCE, chariots became increasingly important in warfare. Early chariots were four-wheeled carts that were clumsy and hard to maneuver. They were still very effective against hapless peasants with spears, however, so it appears that when rival Mesopotamian city-states fought actual battles, they consisted largely of massed groups of chariots carrying archers who shot at each other. Noble charioteers and archers could win glory for their skill, even though these battles probably were not very lethal (compared to later forms of war, at any rate).
The first time that a single military leader managed to conquer and unite many of the Mesopotamian cities was in about 2340 BCE, when the king Sargon the Great, also known as Sargon of Akkad (father of Enheduanna, described above), conquered almost all of the major Mesopotamian cities and forged the world's first true empire, in the process uniting the regions of Akkad and Sumer. His empire appears to have held together for about another century, until somewhere around 2200 BCE. Sargon also created the world's first standing army, a group of soldiers employed by the state who did not have other jobs or duties. One inscription claims that “5,400 soldiers ate daily in his palace,” and there are pictures not only of soldiers, but of siege weapons and mining (digging under the walls of enemy fortifications to cause them to collapse).
Sargon himself was born an illegitimate child and was, at one point, a royal gardener who worked his way up in the palace, eventually seizing power in a coup. He boasted about his lowly origins and claimed to protect and represent the interests of common people and merchants. Sargon appointed governors in his conquered cities, and his whole empire was designed to extract wealth from all of its cities and farmlands and pump it back to the capital of Akkad, which he built somewhere near present-day Baghdad. While his descendents did their best to hold on to power, the resentment of the subject cities eventually resulted in the empire’s collapse.
The next major Mesopotamian empire was the “Ur III” dynasty, named after the city-state of Ur which served as its capital and founded in about 2112 BCE. Just as Sargon had, the king Ur-Nammu conquered and united most of the city-states of Mesopotamia. The most important historical legacy of the Ur III dynasty was its complex system of bureaucracy, which was more effective in governing the conquered cities than Sargon’s rule had been.
Bureaucracy (which literally means “rule by office”) is one of the most overlooked and underappreciated phenomena in history, probably because the concept is not particularly exciting to most people. The fact remains that there is no more efficient way yet invented to manage large groups of people: it was viable to coordinate small groups through the personal control and influence of a few individuals, but as cities grew and empires formed, it became untenable to have everything boil down to personal relationships. An efficient bureaucracy, one in which the individual people who were part of it were less important than the system itself (i.e. its rules, its records, and its chain of command), was always essential in large political units.
The Ur III dynasty is an example of an early bureaucratic empire. Historians have more records of this dynasty than any other from this period of ancient Mesopotamia thanks to its focus on codifying its regulations. The kings of Ur III were very adept at playing off their civic and military leaders against each other, appointing generals to direct troops in other cities and making sure that each governor's power relied on his loyalty to the king. The administration of the Ur III dynasty divided the empire into three distinct tax regions, and its tax bureaucracy collected wealth without alienating the conquered peoples as much as Sargon and his descendants had (despite its relative success, Ur III, too, eventually collapsed, although it was due to a foreign invasion rather than an internal revolt).
Finally, there was the great empire of Hammurabi (which lasted from 1792 – 1595 BCE), the author of the code of laws noted above. By about 1780 BCE, Hammurabi conquered many of the city-states near Babylon in the heart of Mesopotamia. He was not only concerned with laws, but also with ensuring the economic prosperity of his empire; while it is impossible to know how sincere he was about it, he wanted to be remembered as a kind of benevolent dictator who looked after his subjects. The Babylonian empire re-centered Mesopotamia as a whole on Babylon. It lasted until 1595 BCE when it was defeated by an empire from Anatolia known as the Hittites.
What all of these ancient empires had in common beyond a common culture was that they were very precarious. Their bureaucracies were not large enough or organized enough to manage large populations easily, and rebellions were frequent. There was also the constant threat of what the surviving texts refer to as “bandits,” which in this context means the same thing as “barbarians.” To the north of Mesopotamia is the beginning of the great steppes of Central Asia, the source of limitless and almost nonstop invasions throughout ancient history. Barbarians from the steppe regions were the first to domesticate horses, and for thousands of years only steppe peoples knew how to fight directly from horseback instead of using chariots. Thus, the rulers of the Mesopotamian city-states and empires all had to contend with policing their borders against a foe they could not pursue, while still maintaining control over their own cities.
This precarity was responsible for the fact that these early empires were not especially long-lasting, and were unable to conquer territory outside of Mesopotamia itself. What came afterwards were the first early empires that, through a combination of governing techniques, beliefs, and technology, were able to grow much larger and more powerful.