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The Keima Shimari Is Secure
    Keywords: Shape, Tactics

[Diagram]
Diag.: Keima Shimari

We all know the shimari on 3-4 and 5-3 securely encloses the corner. If Black invades, he can't live, can he?

HolIgor: The general statement is that the invader can't live, but the defender kills with so much strain, leaving such cutting points in the wall that the outside influence changes this statement. For one, I like to invade keima shimari. And playing white in the position in the next diagram I'd like add one more stone to defend the corner.



[Diagram]
Diag.: Keima Shimari

Late in the midgame, the corner looked something like this. White's corner shimari was loosely surrounded by my living Black group. I decided to invade the shimari. If I could even force a seki there, it would be a gain for me; and since a play there was sente, I had nothing to lose (as long as White's responses didn't decrease my territory). Plus, I thought my nearby stones would help the invasion. White's answers allowed me to build a small living group, which in turn meant the White stones lacked eyes and were dead. Our later analysis revealed that White had a line of play that would have kept the corner. But the more I play around with it, the more it looks like an invasion on the 3-2 point can force a ko.


[Diagram]
Diag.: White defends with 3-3

After White 10, I played at a. This is silly, because White can kill with b. (If Black c, then White d ensures there's only one eye.)

But if Black takes b, White has to play e. Then Black plays a, and White must capture the ko.

If Black has the better and more numerous ko threats, Black will either get the corner or get compensation elsewhere.

B should just connect at 'f' I think. If W plays to prevent him from making life, B cuts next at 'g' and leads in the race to capture against either group of W stones - the group to the right has only three liberties while the group to the left has only 4 while B has at least 5. - DaveSigaty
Hmm; looks like you're right... - TakeNGive
I agree Black 'f' is enough here. But I think B at 'e' immediately makes Black alive locally, doesn't it? -- dnerra
Dnerra, maybe I read it wrong; but if B at 'e', W at 'b' leads to a ko or bent-4, doesn't it? - TakeNGive
You are right TakeNGive. Dnerra

[Diagram]
Diag.: White defends with 2-3

This is a success for Black -- the Black stones have connected out to live, and White must still scramble to live. (In fact, Black at a seems to kill; and it's Black's turn...)



White's two defenses against the invasion at 3-2 seem to yield either a large loss of territory, or a large ko fight. So I conclude: "the keima shimari is secure" is a controversial statement. Clearly, if the shimari becomes loosely surrounded, White needs an extra move to avoid complication.

Comments? Does White have a better line of play?
- TakeNGive


BillSpight: Controversial? It's just wrong. :-)
Who says that, anyway?

[Diagram]
Diag.: White defense

W 4 looks better than 7. Later, B 9 can make ko.


[Diagram]
Diag.: Black attack

B 1 is the usual attack, I think. :-) If Black can't stand the ko, he can play at 9 instead of 7.


[Diagram]
Diag.: Black attack, var. 1

W 1 is often the killer tesuji. However,


[Diagram]
Diag.: Black attack, var. 1a

B 4 fills at 1.
White's attack fails with Black's cut at 6.

TakeNGive: Thanks Bill; I'll keep these in mind for next time (particularly the 4-3 cut).

TakeNGive: Having looked at this some more, I wonder if there's a better defense of the shimari against a 3-2 attack -- more comments, please?

[Diagram]
Diag.: Does this defense work?

[Diagram]
Diag.: Black 2-3

Black will need 3 or 4 unanswered moves to live, it seems; not going to happen.


[Diagram]
Diag.: Black 3-3

Does Black have something I'm overlooking? - TakeNGive

See the continuation below. B is just too strong on the outside I think. DaveSigaty


[Diagram]
Diag.: Black 3-3 continued


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