Invasion of third line three space extension

    Keywords: MiddleGame, Joseki

Table of contents Table of diagrams
Black's options
Cut
Cutting
Ponnuki
Diagonal attack
Why the diagonal response
Why the diagonal response

Empty triangle again
Knight's move answer
Variation
Keima
Angle play
Jump
Separated

Standard replies to 3 space extension invasion


[Diagram]
Black's options  

The move Black will choose to respond will greatly depend on the circumstances, but mostly these moves reflect the following intentions:

  • a and b attempt to connect the stones, at the expense of a ponnuki for White or in any case sacrificing that stone in the process.
  • c and d show an intention to attack the stone, by threatening to engulf it. Technically c is superior (see later).
  • e is more a defensive move and shows that Black is not in his own sphere of influence and is prepared to let White have it her way.
  • f is a territorial, endgame-ish move

We will have a look at typical sequences fired off by these moves. However, the practical applications will nearly always involve neighbouring stones, which greatly affect the events and therefore also the appropriate choice of move.



Attaching underneath

[Diagram]
Cut  

First of all, if Black is not intending to crosscut with B3 after W2, he should not play B1 in the first place, unless these are endgame tactics. We are thinking of this position as a middle game invasion, so cut and connect are the governing principles.

Black sacrifices to get outside influence, while White gets some territory. Next, White can move out at a (considered correct) or b (unusual), or leave that choice to Black by capturing at c immediately (mild). The cut at d is unreasonable. Again, the presence of other stones may justify any choice.


[Diagram]
Cutting  

This cut is unreasonable.

Attaching on top

[Diagram]
Ponnuki  

Attaching on top is technically the same idea, sacrificing a stone, but obviously with the opposite result. Black connects underneath, while White makes a ponnuki. This sequence can be played when the connection is vital for Black and the resulting influence for White is acceptable, e.g. overlapping with already existing influence.



Diagonal attack

[Diagram]
Diagonal attack  

This B1 shows an attacking mood, which must be justified by the presence of other black stones, such as e.g. at the circled point, where the formation represents a low enclosure low extension invasion. W2 is appropriate, though contrary to basic instinct. We can now envision Black playing a as basic instinct and White jumping out at b.

[Diagram]
Why the diagonal response  

The basic instinct of W2 is unreasonable (barring unusual conditions). B3 puts white on the spot: now she has to play an empty triangle with W4. Imagine a stone already awaiting her at a: the invasion will fail.

[Diagram]
Why the diagonal response  

This W4 is stylish, but Black cuts nevertheless and White will at best live very small. It is not said this line is impossible though: both must take it into account.

symplicity: Won't it often be better for white to capture the stone? Black has some followups like sacrificing two and squeezing, but white escapes any major attack and has gained some rightward strength.

[Diagram]
 


[Diagram]
Empty triangle again  

B5 can also be played here. White remains with the burden of creating an empty triangle or be cut at a.

[Diagram]
Knight's move answer  

A stylish move which may work is this W2.


[Diagram]
Variation  



Weaker attack

[Diagram]
Keima  

The keima is also a typical move for attacking, but Black does not seem to take the advantage he could in this position. Next, a to d are all conceivable. If Black already has a stone at c that again has a major effect.



Angle play

[Diagram]
Angle play  

The exchange B1-W2 seems to confirm White's intent of separating the stones. If this is Black's sphere of influence, then White may play more lightly, allowing the meager connection underneath. If this is White's sphere of influence, then this move can be considered big endgame.



One space jump

[Diagram]
Jump  

Finally, B1 shows a defensive intention, so probably Black is not in a position to attack here. If White jumps too, crossing under with a remains possible for Black, so maybe White should play b, assuming this is actually her sphere of influence.

[Diagram]
Separated  

We recognize the earlier pattern which Black can use to separate the White stone W2. This is rarely a desirable result for White but now the cut at a may work.


Invasion of third line three space extension last edited by tapir on September 11, 2012 - 00:41
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