Zombie siege



Sieges were introduced in Minecraft 1.2.1. At night, Zombies have a chance of invading a NPC Village in packs and attacking the Villagers. Usually, a whole mob of zombies will concentrate on one door or villager, and will break a wooden door down on Hard difficulty. 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.

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. Iron Golems have 100 health (50 hearts) making them rather tough to get through. Zombies cannot break down iron doors in villages, so the player can replace all wooden doors with iron doors and place Pressure Plates for the Villagers to step on in order to open the iron doors, although the outside might have to use another switch, which Villagers cannot operate yet.

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 cannot repopulate, but are a utility mob, meaning they can be built by the Player. Iron Golems also spawn in an NPC Village that has at least 21 Villagers.

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 12w07a by Jon.

As of Weekly Snapshot 12w07a (or 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 usually cannot detect 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 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.