Once the zombie wave becomes something that can be defeated and controlled, people quickly started to adapt to the situation. A total of ten districts started to claim themselves as a "society" and started to build the system.
They had some common and fundamental systems that included many of their last civilizations, such as labor law, tax system, etc. But they also tried to adapt the system that nobody wanted to have back - the war. Yes, "Last World War" was named so that people would never have that tragedy again. However, people never change, and so as War
Now a total of ten districts have to, sometimes against each other, sometimes cooperate with each other. It is not in you and your society's hand how to build the next stage of the world