The placement at 1 allows white to capture four black stones in sente or make a break along the first line threatening the life of the whole group.
Attempts and discussion
is the correct move, which captures the four marked stones, threatening a snapback at a.
is a mistake, which loses the whole left-side group. After
, White wins the capturing race by one move. Even if Black gives up
, he has suffered a great loss.
Black should just give up his four stones and defend his group as a whole. White gains ten points in sente, though: a great result.
--Dansc
Charles How about at
?
Dieter thinks there is more to it.
Black loses about 6 points in gote.
This doesn't work, so ...
at
. Black is killed.
I think this may be the main diagram.
I think that placement gives White sente. HolIgor
connects at
If Black persists then there is another snapback.
Bill: at a is bad. Simply connecting takes sente.
is better than just threatening to take the
stones, allowing Black to play at
.
I believe that this is orthodox play.
If Black is surrounded, at
dies. In that case, this ko looks like orthodox play, unless Black is komaster.
When Black is komaster, White continues as in Holigor's line.