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

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

Stylish replies to 3 space extension invasion

There are many inevitabilities in this great game. The third line, three space extention invasions are common enough to merit a discussion. Ultimately, the opponent's response will be based on specific plans involving surrounding stones. These diagrams are mere introductions to a specific invasion. The student would be wise to scrutinize these positions in order to make their own evaluations, and draw personal conclusions.

[Diagram]

Black's options

  • 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 move, it would be gote here.

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.



Attach on top, by sacrificing 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 underneath to attach on top, 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, as the White stones need settling. Also, the presence of other stones should justify this choice. Food for thought: How should Black continue if White plays 4, at 5.


[Diagram]

Cutting

This cut is more than unreasonable, it's suicide.

Attach underneath, by sacrificing on top

[Diagram]

Ponnuki

Sacrificing on top is technically the same idea, but obviously with the opposite result. Black connects underneath, while White makes a ponnuki on top. 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. It's all about style.

[Diagram]

. . . . . . . . . .

W2 is unreasonable (barring unusual conditions). B3 puts White on the spot: now she has to play an empty triangle with W4. Poor style! 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 live small.

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. The position has a bit of style after she plays Black 5.

[Diagram]

Knight's move answer

A stylish move which may work is this W2. Evaluate this position yourself. What conclusions can you draw from it?


[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. But it just doesn't seem stylish enough.



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 a big, stylish endgame move.



One space jump

[Diagram]

Jump

Finally, B1 shows a defensive intention, rather than stylish. 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. Very stylish indeed.

[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, since it looks stylish.


This is a copy of the living page "Invasion of third line three space extension" at Sensei's Library.
(OC) 2012 the Authors, published under the OpenContent License V1.0.
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