Minecraft wiki entry for Zombie_siege_defense, associated text: These sieges can kill off all the villagers within a couple of nights. (On Normal or Hard difficulties, most or all of the villagers would become zombified, eventually dying in the sun without player intervention) All villages have at least one iron golem to help defend them, but even with this assistance almost any village is likely to become depopulated within a few sieges unless the player provides help. Even if two villagers were to survive, villager breeding is much too slow to recover from the nightly losses. Even with two villagers, they would need to become willing and also need to be at least one unclaimed bed within range before they will breed.