Ko fight example from a pro game - 9

  Difficulty: Advanced   Keywords: MiddleGame, Ko, Game commentary
Moves 215 to 224 (8 at 2)  

This is the final game in the GS Caltex cup between Kim Jiseok (Black) and Lee Sedol. The ko fight starts at B1. The stakes of the ko cover the left to middle stones, including the chain at black+circle, affecting the lower left corner as well. The ko has been briefly analyzed at [ext] http://gogameguru.com/kim-jiseok-wins-18th-gs-caltex-cup/.

Black uses internal ko threats at B3 and B9, while White threatens to revive his lost upper right corner.

Moves 225 to 234 (7 at 1) (10 at 4)  

W2, B5 and W8 continue along these lines.

Moves 235 to 244  

Very soon, the upper right is exhausted and W4 needs to start another ko as a threat to turn around the right side. This ko is huge as well. David Ormerod, 5d says in the above mentioned article at gogameguru that the left side is even larger.

The left side has become so large because Black has strengthened the outside while playing internal ko threats. B1 here is another such move.

B5 resolves the ko at the left side. When W6 captures the ko at the right side, as an execution of the ko threat W4, Black immediately offers the exchange by strenghtening the outside of his left side. W8 resolves the right side ko and B9-W10 is an immediate reduction of its size, forcing White to play inside his freshly gained territory.

Moves 245 to 247  

B1-W2 is another such expense and then B3 finally uses the sente Black gains from the ko fights.

This sente is a surprising feat: it was White who won the last ko (the one at the right side) and usually the player winning the ko gets sente as an extra reward. However, Black's last ko threat at black+circle was not really a threat, rather a fortification of his winning the ko at the left side. On the contrary, it was White who needed to execute his ko threat, by winnin the right side ko, allowing Black to take sente at the left.

Ko fight example from a pro game - 9 last edited by on March 28, 2018 - 23:04
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