Three-space extension

  Difficulty: Beginner   Keywords: Opening

Chinese 1: 拆三 (chāi sān)
Chinese 2: 三间拆 (sān jiān chāi)
Japanese: 三間ビラキ (sangen biraki)
Korean: -

[Diagram]

Three-space extension on the third line

B1 is the three-space extension along the third line, like other extensions a big fuseki point which creates a base for the group and prevents White from attacking around the same point. Compared with the two-space extension, the three-space extension develops more quickly, but has the obvious defect at a where White can invade. This is always a consideration when making the three-space extension.


[Diagram]

Three-space extension on the fourth line

It is also possible to make the three-space extension on the fourth line.

[Diagram]

Mixed three-space extension

This three-space extension could also be called a very large knight's move extension.

[Diagram]

Three-space extension from a wall

Here, Black makes a three-space extension from a wall.

[Diagram]

Completing the shape

Black can follow-up with B1 here to make a robust shape.

[Diagram]

Developing with a one-point jump

B1, a one-point jump, is another alternative for developing from the three-space extension.

[Diagram]

Perfect shape

If for whatever reason White plays the diagonal attachment at W1, Black's marked stone ends up ideally placed after the stand of B2 (see extension from a wall). One line closer at a would be over-concentrated, that is, worse, from the point of view of good development.

[Diagram]

Treating one stone lightly

Depending on the situation, Black may also choose to treat one of the stones in the formation lightly for the sake of development.[1] This type of sequence might be appropriate if White is strong in the upper right, as here. In that case Black a, White b might be good for White, and Black is better allowing W1 in return for B2.

[Diagram]

Variation

If instead W1, B2 gives Black a wall and nice shape.


[1]

[Diagram]

Approaching strong stones

Bill: In this particular situation, B2 is problematic because it approaches White's wall, while extending only to a instead of black+circle allows White to play at b.

[Diagram]

Prepare the way

Bill: To avoid the problems of an immediate extension, B1 - B3 press against white+circle, preparing for a safe extension to B5.



Charles This idea of Bill's, to use the 3-5 point low approach, press, is a bit more subtle than may seem at first glance. For example, B5 is held back one line, giving White much less chance of fighting on this side.


This is a copy of the living page "Three-space extension" at Sensei's Library.
(OC) 2016 the Authors, published under the OpenContent License V1.0.
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