As the nation began to grow, additional support was needed in Mesopotamia to govern the daily affairs of the citizens and to maintain order. Without some form of leadership in the different provinces, Mesopotamia would have been even more vulnerable to outside attacks from other societies. Mesopotamia was organized into smaller city-states. This meant that each city had a separate leader that reported back to the ruler of the nation. The city-state rulers built fortresses around their cities in order to keep them safe.