Zombie siege



'''Note: From at least 1.4.7 to at least 1.6.2, Zombie Sieges fail to start. See for more information. However, normal zombie spawning and behavior as of 1.6 can result in very similar activity.'''

Zombie sieges are in-game events that occur when many zombies spawn in a village. They occur regardless of how well lit or walled off a village is.

Usually, a whole mob of zombies will concentrate on one door or villager, and in Hard and Hardcore mode, will break wooden doors down unless mobGriefing is turned off, giving entrance to the building. This causes the villagers to flee their homes and get attacked by the zombies on their way out.

Mechanics
At night, there is a chance that a zombie siege might occur. This is when a large number of zombies spawn in or near a village, attacking what villagers they can reach, crowding around and pounding on the doors of those they can't. On hard or hardcore mode, they can actually break down the wooden doors of the villagers' homes unless mobGriefing is turned off (this is true of all zombies, not just during sieges.) A zombie siege requires a village of at least 10 houses and at least 20 villagers. Villagers will commonly enter their houses and close the door before any zombies can get in, but they will not attack.

Iron Golems attempt to defend villagers from zombies and other mobs during such attacks. Zombies in sieges ignore light levels and the 24-block minimum distance from the player, but other than that, behave absolutely normally (e.g., they won't spawn on halfslabs or glowstone or anything of the sort, need a 2x1x1 minimum space, etc.). They can also spawn INSIDE houses, making it very difficult to keep villagers alive. However, zombies won't spawn more than 128 blocks away from you, so villages which are far away will remain safe.

Defense tactics
Surrounding a village with a wall and lighting it are staple defenses against normal hostile mobs, especially Creepers. However, they are ineffective for sieges because the zombies can spawn inside even a well-lit village. Zombies may prefer to spawn outside of the village or in the dark when given an access route. If so, this allows players to defend villages by creating pressure plate drawbridges or "kill-channels" that limit zombie entrance.

It is impossible to completely avoid zombie sieges except by sleeping through the night, giving zombies (or any other hostile mob) no time to spawn (unless you play on peaceful). (Note, the actual siege is supposed to start at midnight, but normally spawned zombies near any village will do the same job through the whole night.) If every block within the radius of the village has a half slab on top of it, the zombies will often spawn inside blocks, even solid blocks if there are no transparent blocks nearby, then walk towards the villagers through the wall. Zombie sieges also do not follow the 24-block rule, meaning they can spawn just a few blocks from the player.

Trapping a villager in a ring of fence posts will likely attract Zombies, giving the player/golem a chance to take the zombies down one by one. However, it will also interfere with villager mating if love forms between a trapped and non-trapped villager.

Wolves and Snow Golems may also be stationed to keep the horde at bay, however Snow Golems will be useless in a desert village due to damage incurred from the biome and carry the risk of causing friendly fire with the Iron Golems. Wolves are easy to maintain due to the large quantity of rotten flesh that a horde will yield when defeated.

Dropping a bucket of water followed by a block of TNT is a viable method of clearing large numbers of zombies at once, however due to the pushing effect of water, the zombies may be pushed too far away from the TNT for it to be effective.

Recovery
Villagers repopulate if there is open space in the NPC village. This means that villagers can recover from sieges by having children to repopulate the NPC village, provided there are at least two villagers and enough space in the NPC village. Player-made houses can also cause villagers to repopulate, as long as it is within the NPC village, has a wooden door, and has a block above it (Using this, and by manipulating the way villagers spawn, it is possible to create infinite villager farms to repopulate). Iron Golems lost in the siege will eventually respawn if the NPC village has at least 10 villagers, or can be manually rebuilt by the player.

Unfortunately, these conditions are rarely sufficient to keep villages from being depopulated in short order without active defense by the player. As of snapshot 12w32a, there is an option, albeit a difficult one, to repopulate villages: Curing zombie villagers. Besides spawning as a fraction of ordinary zombies, 50%(medium) to all(hard) of the villagers attacked by zombies will be "infected" instead of killed. Zombie villagers can be turned into villagers by splashing them with a splash potion of weakness, then feeding them a golden apple, and waiting. However, the cure is not instant—it will be necessary to confine the "patient" away from living villagers, and usually to protect them from the sun as well. They will emit red particles until they are cured.

Issues
MC-7432 Seiges fail to start

MC-17630 Zombie pathfinding to unreachable targets causes server lag

MC-7488 Village siege's spawn location is calculated incorrectly (fix included)

Trivia

 * When a zombie is attacking a villager or door, it will usually ignore the player unless the player attacks it.
 * Zombies also attack villager children.
 * In a desert village, sieges cannot occur when it's raining in another biome during the day because the Zombies will burn when attempting to attack the villagers. However, when it's raining in another biome during night, sieges can still occur.
 * Although zombies are the only mob that attacks villagers, Iron Golems still attack other hostile or neutral mobs. This is probably because they can be created by the player for self-defense, not for defending a village; it could also mean that other mobs may lead sieges against villages.
 * If the player spawns a lot of zombies, they will eventually start a siege and all crowd one door.
 * Sieges can occur in player-made villages and mushroom biomes, despite zombies not spawning in mushroom biomes naturally. This is further evidence that sieges are different from standard mob spawning.
 * As of 12w32a, if the player turns mob spawning off with the cheat, sieges can still occur.
 * Early in development, Notch considered adding a gamemode Zombie Siege. It would be you fighting waves of monsters (likely Zombies). This gamemode was, however, never implemented, and has since been abandoned.
 * The chance of trying to start a siege is 10% for each night, but the start may still fail due to other reasons. If it does start one, no other sieges will be started that night.
 * The siege consists of up to 20 extra zombies, all spawning randomly near a single spot chosen randomly inside a square centered with village center and edges twice the village radius (a bug is related to this, though).
 * As of the Redstone Update, zombie sieges can become more dangerous to the player. This is because of the new zombie AI, which makes it so that if a player attacks a single zombie, all of the zombies in the area will pursue that player. Since all the zombies in a siege are grouped together, a player could suddenly be fighting 20 zombies. The Horse Update made zombie sieges even more challenging, as more zombies will spawn if the player continuously attacks zombies.

Gallery
Zombiebelagerung Осада