I'm killing anywhere from 2 to 10 Zombies a turn, that's not counting other civ's and city-states. So I think we hit critical mass when their power became greater than the power of the most powerful troop. So they eventually began wearing down everyone. I only stayed alive because my Zombies were even tougher than the spawning ones. I'm in the industrial era and the spawning zombies are at 90 strength. Also, because I was having zombies kill zombies for a while, if I killed 5 zombies, 5 more appeared the next round. That's not including the random one's that spring up due to other violence. There's been a lot of zombies killed. I'm putting together a group to find the other continent and hunt down the last remaining cities to win. There's just a lot of barbarian and zombie infested wilderness to search through to find them. Two changes I'd like: Zombies killing zombies don't make more zombies. Everyone was dead, no more reanimating the animated dead. Zombies can wipe out a civ. It makes just turtling and killing as many zombies as possible a strategy.