WORLD CIVILIZATION

Detailed explanation-1: -The Sumerians also dug moats outside the city walls to prevent enemies from entering the city. Most people lived in houses behind the walls, while the farms lay outside. In case of attack, farmers fled the fields and took safety inside the city walls. The walled cities of Sumer were like independent countries.

Detailed explanation-2: -The Sumerians looked for ways to protect their cities from neighboring communities. The plains provided no natural barriers. There were no mountain ranges or rushing rivers to keep out enemies. Around the cities, the Sumerians began constructing strong walls out of mud bricks that were baked in the sun until hard.

Detailed explanation-3: -The farmers in Sumer created levees to hold back the floods from their fields and cut canals to channel river water to the fields. The use of levees and canals is called irrigation, another Sumerian invention.

Detailed explanation-4: -The land did not provide any natural protection from invaders. Enemies could easily march into Sumer from almost any direction. This made Sumerians vulnerable to attack, not only from foreign armies, but from other Sumerian cities as well. Wars between Sumerian cities were common.