A fellow go player and I were discussing what we had learned from studying professional go games. He brought up a game that I had never heard of before played in 1573 between Honinbo Sansa (W) and Kashio Rigen (B). These players are more well known for their 1585 game in which a triple ko battle was developed.

The Game is as follows:



This game is interesting to me for a number of reasons, but I think the most interesting developments in this match happen at the bottom of the board where we are presented with two life or death problems: One for white in the lower left corner at move 31(B) and one for black in the lower right corner around move 160 (W). I had a lengthy argument with my friend about whether or not whites lower left group was dead after white played tenuki on move 32.



Since black has sente in this situation can black kill whites group?

My friend argues that there is no variation in which black can kill white unless white makes a mistake and that, therefore, the way it was played out in the real game (with a black play at A2) is the best possible outcome for black. After studying the problem for about an hour, I disagree. I think that even if white plays optimally, black still has a sente move that could kill whites group by taking one of whites three critical eye points at A, B, or C.



In all of the variations I played, black plays at B or C result in life for white, especially since white has some interesting tesujis that can be played. However, a black play at A can result in a ko battle that would decide the life of whites group. I'm not sure if black actually had enough ko threats to win against white in a ko battle, which is probably why they didn't play this variation. I'm still fairly new to reading out situations like this though and I'd like to know if anybody can see something that I missed. What do you guys think?

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I find more and more that my battles on the board reflect my battles off of it.

How does black get ko if white responds to A with B2 clamp?

This is probably why I need to do more reading problems. You're right, if white plays the clamp then white is alive because we end in something like this shape:



In that case a black play at C is probably optimal.

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I find more and more that my battles on the board reflect my battles off of it.