Minecraft wiki entry for Creating_a_village, associated text: If you build a village in a biome where an illager patrol can spawn, be careful: Fences or walls can keep them out easily, but they try to kill villagers, and killing the patrol captain triggers a raid in your own village. If possible, let an iron golem kill the captain; otherwise, you can equip yourself with a milk bucket and try to kill everyone but the captain (if you accidentally kill the captain in the village, drink the milk immediately and hope for the best). Then lead the captain well away from the village (over 32 blocks from the nearest bed) to kill them, and drink the milk before returning to the village.