BQM 457

    Keywords: Question

ferdi: White can also omit W3.

rokirovka: What happens if Black tenukis instead of B2? I faced this in a game today. After dealing with his tenuki and gaining sente I played W3. Black played tenuki again. After dealing with that and gaining sente again I played W5 at a. Amazingly, Black played tenuki again (!) and I got to play W7 at b. Finally Black defended with B8 at c, I played W9 at 2, Black played B10 at d and despite all his tenukis Black came out ahead in the battle in this corner. Surely White can do much better here if Black plays so many tenukis.

Herman: Lets explore some options for white....

rokirovka: Herman, thank you so much for this extensive analysis. It's very instructive and helpful. It will take me a while to digest all of it, but it's greatly appreciated.

Tapir: My 2k first thought tells me to play W3 at W5 in sequence 2 diagram directly. This may be worse than sequence 2, but I'd like to know about the status of the corner then.

Sequence 1 (B2 tenuki)  

Herman: After W3, if black cuts with B4, W5 will capture two stones

Sequence 1.1 (B2 tenuki)  

Herman: However, black can play like this and keep the corner. This result is not good for white, it only gains a few points and is gote.

Sequence 1.1 (B2 tenuki)  

Andy: For the above reason, white should tenuki with W9 instead of capturing the black+circle stones in gote. Since white's wall is more solid, white can extend further. I think the further extension plus the possibility to pick up the black+circle stones later makes this result ok for white.

Sequence 1.2 (B2 tenuki)  

Herman: White can also play like this. Now black's corner is smaller.

Sequence 2 (B2 tenuki)  

This is another option. Black's options along the left are more limited now, and black is walking over the second line.

rokirovka: This reminds me a lot of the "pincer variant" in the standard 3-4, high approach, inside contact, solid connection joseki. The following diagram and comments are from the page devoted to that joseki:

A special plan  

"Black can play at B1 if White's extension frustrates Black plans at the top. (This is bad locally, but may be playable overall.) White's compensation is to fence in Black and create substantial thickness. For both players, knowing how to handle White's thickness is key to playing this variation.

"A word about B5: the connection can also be at a. W8 is a little better than b. (Compare with getting ahead with a one-point jump.)"

Sequence 3  

This W2 is a possible alternative for W7 in the previous diagram. Now, black must make a choice:

Sequence 3.1  

Like this, black is sealed into the corner, and white's position toward the left side is better than in the first diagram

Sequence 3.2  

Like this, black escapes on the outside, but loses two stones. B7 is mandatory, if black defends at W8 instead, white will connect and black's corner will die. After W8, black cannot cut at a, because b is atari, so black should exchange b for a, then tenuki

Sequence 4 (B2 tenuki)  

If black a, white cuts at b and it is the same as sequence 1.2 above.

But what if black b?

Sequence 4.1 (B2 tenuki)  

With the exchange of W3-B4 already in place, black cannot escape to the outside as that will allow white to take the corner.

Sequence 4.2  

If black tries to escape, hw loses the entire corner after W6. So...

Sequence 4.3  

So black has no choice but to play like this. Later, there is a lot of aji is white plays a.

This means that B4 in sequence 4.1 is wrong, as either variation leads to disaster.

BQM 457 last edited by Dieter on March 31, 2009 - 11:56
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