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Kosumi
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  Difficulty: Beginner   Keywords: Shape, Tactics, Go term

The following diagram shows the diagonal shape (kosumi, in Japanese).

[Diagram]
Kosumi



Playing this way for Black may seem simple tactically, but from the point of view of shape that really isn't so. To discuss this intelligently one needs to be very familiar with a few diagonal play reference shapes


The purpose of a kosumi can be to connect, move out?, attack, maintain the cut and so on. Here are a couple of features of the kosumi

[Diagram]
Miai to connect

The kosumi is not yet physically connected but with locally alternating play it can not be cut: if White tries to cut at a, Black plays at b and becomes connected and vice versa. These two points are prime examples of miai.


[Diagram]
Vital points

The four marked points are all vital points of the kosumi shape. White can attack the kosumi at one of these points, when she is in a position to attack of course. See compromised diagonal. Also, ...


[Diagram]
Kosumi

... when White already has a stone here and is strong in the area, playing the kosumi is to be avoided.[1]

Some examples of this shape in actual cases are at compromised diagonals and joseki.



See also:

For diagonal contact there is a whole diagonal attachment path.


Authors: Morten, Dieter, Charles

[1]

Dieter: This is my interpretation of Rob van Zeijst's columns on the kosumi.

Charles Those would be

[ext] http://www.yomiuri.co.jp/igo_e/174.htm

[ext] http://www.yomiuri.co.jp/igo_e/175.htm

[ext] http://www.yomiuri.co.jp/igo_e/176.htm

An example is given there of hebo kosumi (weak player's diagonal). See Attach-extend on the side, tenuki: it's not a trite matter.

I have now added quite a number of further pages stimulated by what's there, and discussion here.



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This is a copy of the living page "Kosumi" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.