What steps did Sumerian city-states take to protect themselves from their rivals?

The Sumerian city-states maintained most of their conflict among cities calling free men to battle when it was needed.

Explanation:

In order to protect the city-states from their rivals the Sumerians called upon every free men to battle. It is important to add that they did not have an standing army, therefore, there was no permanent military to defend the people. Each city-state had its own God and when conflicts arose the high priest and the King called upon the free men to forge their own weapons for battle. While they did have a few trained soldiers the majority was the population. They distinguished the trained military with the use of copper helmets. Furthermore, some conflicts arose due to the water canal developed by them. Some believed to have more control over it than others and blocked it for the water not to flow to other communities this was solved by the creation of a wall around the city. Among the weapons forged by the Sumerian free men were:

Knives Bows Slingshots Axes Among others.

Finally, the Sumerians attributed the fate of a battle to their Gods rather than to its priest.

City-states built up armies/military strength and strong thick walls. Sargon's creation of his empire changed Mesopotomia because it made it all under one ruler. It also make Mesopotomia stronger.