The term derives from the greek "country between the rivers ", and is commonly recognized not only as the land between the Tigris and the Euphrates (the so-called "Fertile Crescent"), but also as one of the first places in the world where developed complex social structures. With those, also developed the firsts military organizations, at first only for defensive purposes, but which, with the passage of time, become instruments of expansion and conquest. It must be underlined that when we refer to state entities, we talk about the development of a single city - state, which expands beyond its walls, towards a relatively adjacent area. The best example for expansionism of a Mesopotamian city-state is the one represented by the city of Babylon. The legends about the wonders of the city and its rulers have come down to our days, and, even today, talking about Babylonia the words pomp and opulence are almost a must. Yet it was not only the Babylonians to play the leading role in those lands: the Sumerians, Akkadians, Assyrians had their respective periods of dominance in the fertile crescent, even at the expense of the city of beautiful gardens. From the point of view of the war, in reality, all these peoples were united by a type of weapon quite peculiar to the region: the war chariot. The first chariots, notoriously Sumerian, drawn by onagers and driven by a charioteer, were composed of a woven basket filled with four wheels. Around the middle of the second millennium B.C. arose a new radical change in the art of war, thanks to the introduction, from neighboring Egypt, the horse. The heavy wheels chariots become to be replaced by lighter wagons with spoked wheels, which are pulled by horses. The intensive use of the horse, and the creation of cavalry units, must be assigned to the Assyrian army. All these features do not really suffer too many changes in the Mesopotamian area, this relative immobility, in conjunction with the perennial conflict between small local lords of the Mesopotamian region, will be the cause of the collapse of the ancient kingdoms of the fertile crescent under the blows of the most powerful and united army of the Persian Empire.
The defeat of the Babylonian army by the Persian king Cyrus II, nearby the city of Opis, marked the end of one among the most glorious Mesopotamian reign and with it, the end of resistance to the Persian rule over the lands of the 'Fertile Crescent'.