Loss-Making Threats

Simple example  

Often seen in beginner games is this loss making threat. Without and , White needs a move inside when a and b are played near the end of the game. just adds a stone to White's prisoners. Loss of one point in sente.

Choice of threat  

Should Black prefer a, b or c here? We assume Black is looking for a ko threat in this part of the board.

Like a failed invasion  

Usually playing c is the worst idea. After , Black's stone looks like abject failure (mochikomi). Black can probably make further threats here such as d, but after White e Black has lost some further points.

Best taste  

From the point of view of avoiding possible loss, Black's best choice is this threat. When White answers at , looks like a kikashi, that is, has some positive effect in addition simply to being sente. Of course has aspects of aji keshi - just about any ko threat does (see the aji machine).

Not clear  

It isn't clear without more information whether is a loss. After 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 at e, in which case Black will probably be satisfied.

Summary: Threats that come in deeper risk loss; threats from outside risk little.

Charles Matthews

Local threat  

Suppose White plays as a threat during the ko fight in the corner.

A change in the position  

If Black answers it at , and White later wins the fight, it is a bit disappointing for White to have made this exchange.

Poor exchange for White  

That is, in this position the exchange / looks better for Black. If not for it, White could invade deeper at any of a.

Local threat 2  

If Black wins the ko, White will regret the exchange of for , since it loses 2/3 point, on average, by comparison with the position when Black wins the ko without that exchange.

Black wins ko  

(We assume that is sente, threatening to invade White's surrounding territory.)

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.

For the worst kinds of loss making ko threats see kill Yourself in sente