Ko position from one-space low pincer

  Difficulty: Advanced   Keywords: Life & Death, Ko
Starting position  

In the page on the one-space low pincer, it is mentioned that this corner is ko if Black plays first. There are two ways to start this ko, but one is clearly better than the other.

First ko  

The 'wrong' way to start a ko is by this sequence. If Black wins the ko in the conrer, White dies. If White wins it, she lives.

Second ko  

The 'correct' way to start ko is with B1 and B3 here. This ko is more pleasant for Black than the previous one for two reasons:

  1. In this diagram, if Black wins the ko, he can take the stones off the board. This means that White has no aji left whatsoever. In the other diagram, a small amount is still left.
  2. In this diagram, White has to make the first ko threat, whereas in the other diagram, Black does.

Anonymous: Why not skip B1 in the second ko, playing directly B3 ?

Chaz: Skipping B1 gives white more aji because black winning the ko doesn't capture the marked stones (see Reason 1 in why second ko is better). Thus the exchange of B1, W2 is considered the proper way to start the ko.

Second ko (improper set up)  
Second ko (white deviates)  

What if White ignores B1 and plays to live without ko? What is Black's response to W2? /Solution


Ko position from one-space low pincer last edited by Chaz on January 4, 2011 - 19:45
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