@C i t i z e n  so it's not that 2 contries were at war , but I think people didn't know that monsters have appeared at first so they thought that their could be war between contries .
But now that a whole lot of monsters started appearing, and the military couldn't handle them they nuclear bombed the area .
So probably the zombies were the target of military but they became radioactive zombies . The radio active whatever it's called did ffect for sometime but after that it dissipated and now people are able to come out of their places . But the threat of monsters is still their . It's not resolved and the human are going crazy and killing each other for survival , instead of monsters and actually regrouping and fighting together .