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Suicide
Difficulty: Advanced
Keywords: Tactics, Rules
The term suicide (or self-capture) refers to a move which is played such that the stone that is played has no liberties. 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.
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 white 1, taking 3 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.
But sometimes suicide also makes a difference for the outcome of a semeai. 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 1 to 5, then captures at 7, resulting in the next diagram.
Playing at white 1 to prevent Black from getting two eyes will not help White. Black plays atari at 2, 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.
If suicide is allowed, White does have a recourse in this situation: She can play the suicide move of white 2. The result is shown in the next diagram.
After white 4, the position is a seki; neither player can make any useful move - so this time, White lives. If Black plays 1 or 3 at 2 or 4 or A, the position is seki as well, 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:
Main author:
This is a copy of the living page "Suicide" at Sensei's Library. (C) the Authors, published under the OpenContent License V1.0. |