Suicide

  Difficulty: Advanced   Keywords: Tactics, Rules

Chinese: 不入 (bu4 ru4)
Japanese:
Korean:

The term suicide (or self-capture) refers to a move which is played such that the stone just placed has no liberties, but all opposing stones still have.

Suicide moves are forbidden under Japanese rules and Chinese rules; but some other rulesets, such as Ing rules, New Zealand rules and Tromp-Taylor rules, do allow suicide, at least when it is suicide of more than one stone.

A suicide of one stone does not change the position on the board, and therefore may be forbidden or equivalent to passing, depending on the ruleset [1].

Suicide of more than one stone can, however, be a useful move.


[Diagram]

Suicide as a ko threat

The simplest, and best known, situation where suicide can make a difference is as a ko threat. In this position, the black group is alive. However, if White is allowed to play the suicide move of W1, taking three white stones off the board, Black will have to come back at the same point to make two eyes. If suicide is forbidden, then White has no ko threat here.


[Diagram]

A capturing race

But sometimes suicide also makes a difference for the outcome of a capturing race. In this diagram, if White is not allowed to play suicide, she is dead. There is no way for White to avoid that: Black first fills up two liberties with B1 to B5, then captures at B7, resulting in the next diagram.

[Diagram]

Black wins

Playing at W1 to prevent Black from getting two eyes will not help White.

Black plays atari at B2, and White is dead.



Note that these diagrams are just used to show that White is indeed dead - Black need not hurry to take the stones off the board.

[Diagram]

Suicide permitted

If suicide is allowed, White does have a resource in this situation. She can play the suicide move of W2. The result is shown in the next diagram.

[Diagram]

White wins

After W4, the position is a seki; neither player can make any useful move - so this time, White lives. If Black plays B1 or B3 at W2 or W4 or a, the position is still seki, each player having one eye and no external liberties.


[1] The status of self-capture of a single stone in various rulesets which allow suicide is as follows:


[ext] Suicide is painful:

A very unusual incident occurred in the first round of the 15th Korean Kiseong tournament (2003-10-02). Cho Hunhyun 9p was forced to lose a game (against Choi Cheolhan) because of an illegal move. You can see the game record at the time of the infraction at [ext] go4go (or at illegal move). Cho obviously intended to take the ko in the lower left corner when he made an illegal suicide play instead (on the lower edge). Such a mistake is extremely rare in professional tournaments.


Main author:


This is a copy of the living page "Suicide" at Sensei's Library.
(OC) 2005 the Authors, published under the OpenContent License V1.0.
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