L+2 group

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    Keywords: Life & Death

The L+2 group is an L group with a leg on both sides.

Table of contents Table of diagrams
L+2 group
First hane
First hane: failure
Second hane
Lives, but...
When Black ignores the sente move
When Black ignores the sente move
Attack at 1-2
Attack at other 1-2
Attack at 1-3
Attack at 2-2
L+2 group
L+2 group with a weak leg
White makes a rogue ko
L+2 group with a weak leg
L+2 group with a weak leg
Follow up (1) after W's attack.
Follow up (2) after W's attack.
After Black 1...

[Diagram]

L+2 group

The L+2 group is alive. The corner territory can be reasonably counted as 6 points. We will have a look at: the defense against the hane from either side; how to deflect attacks from within; and the status of this group when White has a stone on either of the marked points.


1. Defence against a hane

[Diagram]

First hane

Against the hane from the short side, one should defend at the 1-2 point. Now there are two sure eyes at the circled points.

See also /Discussion

[Diagram]

First hane: failure

Answering at the 2-2 point leads to seki - or to ko if that is what Black really wants (see bent four in the corner).

[Diagram]

Second hane

Against the hane from the long side, one should defend at the 2-2 point. Now there are two sure eyes at the circled points.

[Diagram]

Lives, but...

Suppose the marked stone is added. Now W3 is sente. If B2 was played at a then the addition of white stones at W3 and b would not be sente at all.

[Diagram]

When Black ignores the sente move

Black cannot play at a to secure the second eye.

[Diagram]

When Black ignores the sente move

One eye to none, White wins the capturing race.



See also /Discussion.


2. Attacks from within

[Diagram]

Attack at 1-2

[Diagram]

Attack at other 1-2

[Diagram]

Attack at 1-3

Here a and b become miai.

[Diagram]

Attack at 2-2

Here a and b become miai.


3. An extra stone

In many of the variations above, Black suffers from shortage of liberties as soon as one of the circled points is filled by White.

[Diagram]

L+2 group



See L+2 group with descent.


4. Weak leg

[Diagram]

L+2 group with a weak leg

If Black has a weak leg, White can kill with a rogue ko.

[Diagram]

White makes a rogue ko

Black cannot play atari at a because of a shortage of liberties.


5. Weak leg (2)

[Diagram]

L+2 group with a weak leg

In this shape, white can make ko fight with White a.


[Diagram]

L+2 group with a weak leg

B2 and B4 is best response of black.

[Diagram]

Follow up (1) after W's attack.

[Diagram]

Follow up (2) after W's attack.

This is ko fight.


[Diagram]

After Black 1...

Above shape can be made by black's probing move - B1, in real games.


See also


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This is a copy of the living page "L+2 group" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.
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