L+2 group with descent

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Table of contents Table of diagrams
L+2 group with short-side descent
The tesuji
White's mistake
continued
When Black wins the ko
with short-side descent
L+2 group with long-side descent

L+2 group with descent I

[Diagram]

L+2 group with short-side descent

It is said that the L+2 group is alive. However, when there is a descent at black+circle, it is not exactly the case.



The tesuji

[Diagram]

The tesuji

The tesuji of B1 and B3 exploits the black+circle stone.

[Diagram]

White's mistake

What works for the L+2 group case does not work here. The atari at W4 is a mistake. After B7, due to shortage of liberties, White is unable to prevent Black from connecting the three stones at a.

[Diagram]

continued

White's best response is W4, leading to a two-stage ko. White uses capture at a as a local ko threat. (Though some English books suggest B5 at B7 throw-in immediately, it needs another approach move at B5.)

[Diagram]

When Black wins the ko

When Black wins the two corner kos, Black connects at B1 to finish White off.

Alex: Looks like a good way for a Moonshine Life position to arise. Now White just needs to arrange for a double ko somewhere else... :-)


Variation

[Diagram]

with short-side descent

It is worthwhile to discuss this variation. This W2 leads to a direct ko with Black taking first, so is inferior to the main line. B3 is the only move to avoid seki.


L+2 group with descent II

[Diagram]

L+2 group with long-side descent

The descent at black+circle does not affect the status of the group, which means that White is unconditionally alive. Defence against Black's attacks are identical to those listed in L+2 group.



This is a copy of the living page "L+2 group with descent" at Sensei's Library.
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