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September 1998's Go Answer of the Month

This situation occurred in one of Robert Salkeld's games at this year's Mind Sports Olympiad. In that game, Black died.

Dia 1 - Status?

Dia 1

Note that this is an open ended question in as much as - at the time of posting the question - the status of this corner group has not been determined.

The answers presented here are not definitive, they are the result of my personal investigations and there may be some tesuji or sequence I have not studied which changes the result. Please let me know if you find such a sequence.

Dia 2 - Black to play.

Dia 2

There are many possiblilities, but after black 1, none show any signs of killing Black. This diagram is just one conceivable sequence to show how easily Black lives with first move.

With White to play first...

Dia 3 - The L+1 group.

Dia 3

After black 4, we have the L+1 group which is a well known case of 'first player wins'. Here the next player is White, so Black dies if he plays this way.

Dia 4 - Making eyes.

Dia 4   White 1 and 9 at triangle.

These sort of attempts lead only to one eye.

Dia 5 - Expanding Black's eyespace.

Dia 5

Expanding Black's eyespace with a move like 2 seems often to end as a "bent four in the corner".

A recent email showed me that this requires comment.
"Bent four in the corner" - usually recognised by three stones in a five space area in the corner - nothing 'four' about it, is a situation where capturing the 3 corner stones is futile. At the post-dame end of the game the '3-stone' player can remove the outside liberties before setting up a ko to kill the stones. As there are no longer any ko threats, he achieves this. This is a 'rule' in the Japanese ruleset, some rulesets require it to be played out, practically always with the result described. IE Black dies here.


Black can play and live. White can play and kill.

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