Fighting Zombies: Lonely City and Abyss

A certain country understands that they are completely unable to pose any threat to Country Z on the frontal battlefield, so now they are starting to play dirty tricks. (This is the first one) A crisis breaks out in a border town. The outside world was turned upside down, and Chen Mo, a former senior biological researcher, continued to study his unfinished projects in his underground fortress. External survivors, various surviving organizations, etc. All tried to attack his fortress and kidnap him. . . .