Zombie siege

A siege in progress.

Zombie sieges are in-game events where many zombies spawn in and attack a village.

Mechanics

At midnight each night (tick 18000 in Minecraft time), a zombie siege is determined to occur somewhere in the overworld that night with a 10% probability. If a siege has been determined to occur, attempts are made each tick to start the siege until either an attempt is successful or the sky light level reaches 12 due to sunrise, although the reduction in sky light level from a Thunderstorm allows siege start attempts to continue well past dawn.

Siege start checks

The decisions whether to start a siege, spawn a siege zombie, or to abort any siege start attempt are made while the game rule doMobSpawning is enabled. If the rule is disabled after the decision to attempt a siege was made, and then enabled again during another night (even before midnight), the decision still stands until a new decision is made at midnight, a siege starts, or the start attempt is aborted due to sunrise or Peaceful difficulty. Disabling the game rule also halts the spawning phase of an active siege, continuing with the remaining spawns when mob spawning is enabled again, unless conditions for aborting the siege are met. There is no way to force the game to start making siege attempts.

Players who are not in spectator mode can trigger the night's siege if they are in an area that is considered part of a logical village and are not in a biome with the without_zombie_sieges tag. The start check iterates over all players in the dimension every tick, until either a player satisfies the starting conditions or the siege attempt is aborted as described above. The game does not attempt to start sieges in peaceful difficulty, and any active decision to make such attempts is canceled when the difficulty is set to Peaceful, and not resumed if difficult is set higher again.

Ten attempts are made per player to choose a random siege starting point. First, a random location on a horizontal circle with 32 blocks radius around the player is chosen as the starting point, then that location is used to find a potential spawn location for a siege zombie as per the zombie spawning logic described below. If this successfully finds a valid zombie spawning point, the siege is started at the chosen starting point. If all ten starting points fail to find valid spawning locations, the checks pass to the next player.

Zombie spawning

During a siege, 20 zombies try to spawn in intervals of 2 ticks. For each zombie, 10 attempts are made to randomly choose a valid spawning point on the surface (i.e. highest non-air block at given horizontal coordinates) within a 16×16 horizontal distance around the chosen point. If a valid spawn point is found, the zombie is spawned. Failed spawns are not repeated, leading to fewer total zombies spawning for the siege.

Zombies spawned within a siege ignore player proximity, the presence of other mobs, and whether an area would usually spawn zombies. Only the minimal spawning conditions are checked:

• Light level must be appropriate for zombie spawning.
• The surface block must allow zombie spawning on top.
• The block must be within a logical village.

Zombie villagers, husks and drowned are never spawned as part of a siege, but all other variations (e.g. baby, jockey, and equipment) are determined as for normal random spawns.

The zombies that spawn as part of a siege behave in the same manner as normally-spawned zombies; they attack all villagers within sight, and villagers and iron golems react accordingly. The zombies despawn as usual if the player is far enough away.

Recovery

If at least two villagers survive the siege, the villagers can breed and repopulate the village. Without player intervention, however, it is likely for villages to be wiped out by sieges and randomly-spawned zombies, and all the villagers would be either dead or zombified.

Even if no villagers survive, a village may be repopulated by curing zombie villagers, or by luring in villagers from another village.

Video

Note: This video is from Java Edition 1.5, so the changes were not introduced.

History

[hide]Java Edition Classic
June 10, 2009							Notch promised to have an expansion pack adding zombie sieges, but never made it.
[hide]Java Edition
1.2.1			12w07a				Zombie sieges added by Jon Kågström.
							Villagers repopulate villages based on how many houses are available.
			12w08a				Added iron golems, which protect villagers against attacks such as zombie sieges.
1.4.7							Zombie sieges no longer occur due to a bug.
1.8			14w25a				Zombie sieges may again occur.
							The start positioning of zombie sieges has been fixed: sieges now start near the village perimeter rather than anywhere within the village.
1.14			?				Siege mechanics significantly changed due to changes in village determination: sieges can now start anywhere in a village, the starting point is always 32 blocks from the triggering player, minimum village population limit removed, zombies now always spawn on the surface, and spawns consider light levels.
1.14.3			Pre-Release 3				The bug that caused zombie sieges to never occur has been fixed.
1.19			22w11a				without_zombie_sieges tag created to replace the hard-coded check for mushroom fields biome.
[hide]Pocket Edition Alpha
v0.9.0							Added zombie sieges.
[hide]Bedrock Edition
1.11.0							Zombie sieges have been removed, due to a bug.
[hide]Legacy Console Edition
Xbox 360	Xbox One	PS3	PS4	PS Vita	Wii U	Switch
TU12	CU1	1.00	1.00	1.00	Patch 1	1.0.1	Added zombie sieges.

Issues

Issues relating to "Siege" are maintained on the bug tracker. Issues should be reported and viewed there.

Trivia

• Sieges can occur on mushroom fields if the triggering player is in an adjacent biome.

Gallery

Screenshots

• 

  A group of zombies, two of which are villagers, breaking down a wooden door.

• 

  An iron golem killing a zombie during a siege, preventing the zombie from breaking down the door.

• 

  A siege ending because of the zombies burning in the daylight.

• 

  A siege in a desert (where it never rains) during rain in another biome. One zombie burns in sunlight while two others are protected by their helmets.

• 

  A zombie attacking a villager while the other one is trying to run.

• 

  3 villagers taking cover in a large house during a zombie siege.

See also

• Raid
• Zombie