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Loss-Making Threats
Path: ForcingAndInitiative · Prev: KoThreat · Next: KikashiSenteDiscussion Path: Mistake · Prev: KyuDisease · Next: Low Path: SecondCourseOnKo · Prev: LocalKoThreat · Next: ThereAreNoKoThreatsInTheOpening
Keywords: Ko
Generally playing a threat just because it is sente, and for no other reason, is a typical novice mistake. When it comes to ko fights, this becomes a more difficult discussion. Ko threats that are loss-making have a special name, sonko, in Japanese; and to become a ko expert one has to pay great attention to the idea. You do need ko threats in a ko fight. Playing loss-making threats is clumsy, and assumes that the ko fight is all that matters. That need not be the case.
Should Black prefer a, b or c here? We assume Black is looking for a ko threat in this part of the board.
Usually playing c is the worst idea. After White plays at 2, Black's stone looks like mochikomi. Black can probably make further threats here such as d, but after White e Black has lost some further points.
From the point of view of avoiding possible loss, Black's best choice is this threat. When White answers at 2, Black 1 looks like a kikashi, that is, has some positive effect in addition to being sente. Of course Black 1 has aspects of aji keshi - just about any ko threat does (see the aji machine).
It isn't clear without more information whether Black 1 is a loss. After White 2 Black has the play at d, and one should know before coming to a judgement whether White could play e or f. If White can play f and capture everything that would constitute a big loss for Black, but the fight might be big enough to distract attention from the ko. White might play 2 at e, in which case Black will probably be satisfied. Summary: Threats that come in deeper risk loss; threats from outside risk little. Some examples of a local ko threat that may make a loss. Example 1:
Example 2:
If Black wins the ko, White will regret the exchange of
(We assume that Therefore, even though White has a local ko threat, she should play it only if it is crucial; for instance, if it is necessary to win the ko or if it forces Black to make a losing ko threat of his own. Path: ForcingAndInitiative · Prev: KoThreat · Next: KikashiSenteDiscussion Path: Mistake · Prev: KyuDisease · Next: Low Path: SecondCourseOnKo · Prev: LocalKoThreat · Next: ThereAreNoKoThreatsInTheOpening This is a copy of the living page "Loss-Making Threats" at Sensei's Library. ![]() |