# why ever make the J-group? [#1704]

AndyPierce: why ever make the J-group? (2009-01-12 17:32) [#5626]
J group

If the J-group lives or dies according to sente, but the straight-J with at a can only be killed with ko, why ever make a J-group? Why not always decend to make the straight J?

always do this???
X
HermanHiddema: Re: why ever make the J-group? (2009-01-12 18:38) [#5627]

Hmmm, well, why does anyone ever make a bad move? :-)

Most people that make the J-Group do so because they don't know that it is dead, or don't know that they can get ko with the straight J-group. Or they make it in a situation where the straight J group is not available, eg:

Unkx80: Re: why ever make the J-group? (2009-01-12 19:24) [#5629]

If the J-group lives or dies according to sente, but the straight-J with at a can only be killed with ko, why ever make a J-group? Why not always decend to make the straight J?

By and large, I agree with you. But this is only after we know the results for the J-group. The proof of this "theorem" is nontrivial and requires some requisite knowledge to understand.

By the way, the J-group with hane is also known to be alive. This result is used in the 4-4 point double kakari tenuki joseki, see joseki-related life-and-death example 4.

AndyPierce: Re: why ever make the J-group? (2009-01-12 20:57) [#5632]
Kikashi before living

The joseki page gives this line.

why not this?

If there's no disadvantage to the straight J, why doesn't black do this ? He must be afraid of this for some reason, if it makes sense to play a instead of .

Unkx80: Re: why ever make the J-group? (2009-01-13 16:48) [#5650]

If the attacker plays first, basic J-group without hane means death, while basic J-group with hane means unconditional life.

The straight J-group with hane deserves its own section. If I am not wrong, Black stands to lose two stones to ensure unconditional life.

eastmelody: Re: why ever make the J-group? (2014-06-07 08:14) [#10135]

I think Black can kill straight-J unconditionally.

always do this???
78.20.151.185: Re: why ever make the J-group? (2014-06-07 17:09) [#10137]
Ko
Ko