Tsumego From Games 20

    Keywords: Problem

This came up today in a game. White thought that the group in the corner is alive. Is this so? --unkx80

Status? (All outer stones are alive)  

What happened during the game  

During the game, Black played B1. After B5, a and b are miai, and White is killed by shortage of liberties. White resigned soon after that.

Also dead  

W2 provides another path of resistance. However, up to the B7, White is dead in bulky five. It does not matter if W2 is played at W4 first.


Correct play by White  

The descent by W2 is the correct move which both players failed to see. To stop White from connecting underneath Black may play at B3, but then W4 ensures life. After that, a and b are miai.

The actual solution  

The real solution is actually the placement at B1. The best sequence is from W2 to B7, which results in a rogue ko.

Dieter: the W4-B5 exchange makes it a rectangular six in the corner with one outside liberty. In that case, the 1-2 point makes it ko.

Not as good  

W2 followed by W4 is yet another variation. Up to B7, it is still a ko, but the ko is worse off for White compared to the previous diagram.

Bill Spight: A wonderful position, unkx80!

Because of the throw-in the ko is unusual, but this case has another quirk, thanks to the local ko threat to connect. I'll discuss this further at rogue Ko.

unkx80: Thanks. But shamefully, I was Black.

Tsumego From Games 20 last edited by BillSpight on November 13, 2003 - 03:46
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