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Tripod Group
Difficulty: Beginner
Keywords: Life & Death
The black group in this diagram is called 'tripod group'. It is one of the smallest shapes in the corner that is alive as it stands. Black needs to remember the correct reply to two white attacks.
This is the first attack. After 2, Black still has a live shape in the corner. Alain : This is true in most positions, but black should be careful when white plays in the neighbourhood!
One should keep in mind that a white move at one of the marked points threatens to locally kill the corner. Of course, white has to be very strong at the outside if she wants to play like this.
This is the second attack. In this context, Black must be careful not to make the following 'sente' exchange.
The reason is that the status of the corner has now changed to ko. White can set up this ko following the next diagram.
Black is now forced to win the ko if he wants to keep the territory in the corner.
The a-b exchange creates a shortage of liberties. After 5 in the previous diagram, if black hadn't exchanged a for b, he could live unconditionnally.
The throw in at 4 is the key move. After 6, if white takes two stones at 'a', black will take back the white stone at 'a'.
This variation with white 5 taking the ko results in the same result as the previous diagram - unconditionally alive.
--unkx80
Yesterday 24/9/01 we practiced the TripodGroup at our club meeting. In response to White 1, Black 2 is the intuitive move for many players. We were wondering why this would be "wrong". I think that under these conditions, with all that open space around, this is actually a good move, but the tripod often appears in enclosed space, so that a White attachment at A becomes dangerous. Moreover, if there were an escape route along the left side, White would have blocked at 2 instead of 1. So, Black 2 at A is the main line.
So, Black escapes, but loses his corner territory and, what's more important, his EyePotential there. Practical application
This is a position from the final game of the 2000 German Championship, between Franz-Jozef Dickhut (Black) and Christoph Gerlach (White). Black wanted to do something about the upper left corner.
So he invaded at 1. White can play 4 one point higher, but then Black has a cut at 4, which he can use to isolate the two white stones at the top. Either way Black creates a nice position.
From an endgame point of view, it is better for White to play like this diagram: Black will end up with two points less in the corner. However in the game White followed the previous diagram, probably because he didn't like the remaining weaknesses on the left side following this sequence.
This is a copy of the living page "Tripod Group" at Sensei's Library. (C) the Authors, published under the OpenContent License V1.0. |