Zombie siege



Sieges were introduced in Minecraft 1.2.1. At night, Zombies have a chance of invading a NPC Village in mobs and attacking the Villagers. Usually, a whole mob of zombies will concentrate on one door or villager, and will break a wooden door down. When attacked, the villagers will run out of their houses and flee from the zombies, which chase after them. The Zombies are known to spawn around the outer section of the Village, rather than spawning in the wilderness and dark areas as usual, and then invade a Village. Currently, only these functions are known to be implemented to the game, but there may be more features in future updates.

Defense
Villagers themselves do not defend others or themselves at all, and only flee from hostile mobs (such as zombies), and if this happens they will run until they find their house, where they will close themselves in.

Iron Golems defend Villagers from Zombies and other mobs during such attacks and all other times, and can naturally spawn in a 16x16x16 area around the center of the villages. Zombies cannot attack Iron Golems.

The best defense, although rather time consuming, is to surround the whole village with Fences or even better garrison it within a 2-3 blocks tall wall, so that the zombies will lose time trying to path through them, giving the Iron Golems more time to reach them and fend them off, or stalling them until sunrise. Adding a remotely-controlled gate or drawbridge will make the fort virtually impenetrable, as long as the inside is lit thoroughly to prevent mob spawning.

Wolves and Snow Golems may also be stationed to keep the horde at bay, although the latter carry the risk of causing friendly fire with the Iron Golems. The former are also easy to maintain due to the large quantity of Rotten Flesh that a horde will yield when defeated.

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 3x3 space inside.

Iron Golems lost in the siege will eventually respawn if the NPC Village has at least 16 Villagers, or can be manually rebuilt by the Player.

History
On June 10th, 2009, Notch promised to have an expansion pack for Zombie Siege, but never achieved it. The first part of the project was added in Snapshot 12w07b by Jon.

As of Weekly Snapshot 12w07b, Villagers repopulate if there is open space in the NPC Village.

In Snapshot 12w08a, Iron Golems were released to specifically protect Villagers against attacks such as a Zombie siege.

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.
 * 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.
 * Amusingly, in creative, if you spawn a lot of zombies, they will eventually start a siege and all crowd one door.
 * Zombie sieges are more common when returning from the Nether and entering in a loaded game. This may be linked with chunk loading. (Confirmed as spending many Minecraft days near Bedrock, mining away-from a Village, upon surfacing once 3 Different groups of 5 Zombies, so Roughly 15 [some disappeared while pursuing others] spawned, a record for one player).
 * Lighting does not seem to have any effect on sieges. (Confirmed, both for lone Zombie sightings and the same Roughly 15 seen as of Snapshot 12w22a within basically the same small on-screen area).
 * Sieges can happen in player made villages.