Since the purpose of fortifications is the protection of inhabitants and goods inside a building or a settlement, the most durable materials available were chosen for their construction. In most areas of the ancient Near East, this was stone. In the alluvial plains of Mesopotamia, mudbrick was used but in sufficient thickness to make attacks difficult. Urban installations were vulnerable because of their stored grain and other valuables. As early as the Uruk period, towns in the more exposed regions were surrounded by rectangular defensive walls, with towers and gates. In the Early Dynastic period,when rivalries between citiesin Mesopotamia became widespread, such installations became a common feature of all cities. The best known is the city wall of Uruk, which was nearly 9.5 kilometers long. The Sumerian text “Gilgamesh and the Agga of Kish” describes the conflict between Uruk and Kishand the psychological stratagems used to win access to well-defended cities.
In the Iron Age, technologies of warfare became more advanced as the machinery and tools for attack became more durable than the earlier bronze weapons. As a result, the fortifications became stronger, with regularly spaced watchtowers and projection bastions, crenellations, and gate towers with lateral guard chambers. In the more rocky regions (e.g., Assyria), fortifications were built on stone outcrops and steep hillsides (e.g., at Assur). In the mid-first millennium, Nebuchadrezzar II built the famous walls of the capital Babylon, an undertaking made even more challenging by the fact that the river Euphratesran right through the city. The walls close to the water had be constructed of baked brick, in places up to 25 meters thick. According to the descriptions of Herodotus, the walls were wide enough for two teams of horse-drawn chariots.
Historical Dictionary of Mesopotamia. EdwART. 2012.