Mixed four space extension, invasion

    Keywords: MiddleGame, Shape, Tactics

Many 2 dans don't know about the differences between the following two shapes, but any kyu can understand it once it is explained:

[Diagram]

Good for Black

This W1 is often questionable, as after the cross-cut B2 and B4 are in good connection to the original black stones, as shown by this example sequence.

[Diagram]

Good for White

In this shape, B2 and B4 are in no good connection to the existing black stones. White has many ways to cut conveniently, leaving one of the two black stones badly damaged.

[Diagram]

Summary

If White wants to separate the black stones, he has to enter at one of the points marked a. If White plays there, Black has to give up any hope of connecting, and should instead attack the White stone. If White instead enters at one of the b points (not often the right choice), Black can almost ensure a connection with the cross-cut.

[Diagram]

Question

jwaytogo: Anyone know if the attachment invasion at 'c' is a feasible move? If the four-space jump is similar to the three-space jump (see Attachment invasion of mixed three space extension), then one variation, I assume, is as follows:

[Diagram]

One variation

My concern is that this result is probably better for black compared to the result in the 3-space invasion. I am wondering if the four-space extension could be exploited more? Note that the ladder has to be good for white.

Bill: This sucks for Black. Black is very overconcentrated. If Black had the ponnuki already, would he play black+circle? (It's even worse in the next diagram.)


jwaytogo: I agree with you entirely, but look at a typical end result from invading a three-space extension, where the stone at black+circle is one space to the right. Clearly this is a worse result?

Bill: I don't know what you consider typical. This may be better than that, but it still sucks.

jwaytogo: I personally find none of these results acceptable for black, unless the ladder is in black's favor. If this is the case, white would choose another variation. Black could also connect at W7 instead of cutting at B4.


My question is not so much directed at the efficiency of the end-result, which is undoubtedly bad, but whether the variations for the three-space extension and four-space extension are similar, and if there are differences, what are they? I only gave this development as an example. I am assuming that one can respond to the attachment invasion of a four-space extension at any of the points labelled with a red square in the first diagram above.

[Diagram]

Alternative continued from B6 above

Semper: That is what I would call being pulled around by the nose :).

instead of answering at 3 with 4, why not just defend directly with 4 where the white five is ? or else at a ? sure, your stones are cut, but you have a short wall on either side plus base to make territory. He'll have to choose to attack one side or the other, and either attack would be slow. It would give you time to make some other decision. Plus, you could probably easily live on either side played right ,).

My guess is that you would be scared of letting him build a small wall facing the center. while he is attack the right side, wedge out on the left and use your body. Or else stay and fight just long enough on the right side to live though you'll be helping him build an outside wall, it just depends on who you're playing and what you feel like. I wonder how you like this idea ? :)

[Diagram]

Alternative 2 continued from B6 above


This is a copy of the living page "Mixed four space extension, invasion" at Sensei's Library.
(OC) 2011 the Authors, published under the OpenContent License V1.0.
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