In the fourth game of the Kisei title match between Iyama Yuta (black) and Yamashita Keigo there was an interesting tenuki by Iyama which I had some thoughts and questions about. I'll do more detail later, but essentially my question is "Why did he tenuki move 32 b4, if capturing it was sente?" as when white got b6 later that seemed rather nice for him.



For his tenuki Iyama attacked white's lower group and succeeded in capturing it in gote, in exchange for white getting a ponnuki outside and quite a few ko threats. p3 still had a lot of aji and later lived via ko with a lot of points and sente as black needed o2 to keep the dead stones dead. So that kill didn't seem so satisfactory for black to me. But never mind that judgement, let's assume Iyama considered it a decent profit to spend gote on.

So if after b4 black captured the stone to live in the corner would white finish off on the outside with c7 gote? If yes then black could play the attack on the lower side and, assuming the same sequence happens, capture the group in gote and then white would have sente to play some big move elsewhere like the top side or activate p3. As it was in the game white used his sente after black killed the bottom stones to play b6 which seems like a more urgent and bigger move than the others available, tedomari if you will. So if black could have lived in the corner in sente then captured the lower side, ending in white sente I think it would have been better than the game. Do you agree? Or maybe living in the corner isn't so nice as white has nice yose at b1 so the corner is smaller.

The other option is white wouldn't finish with c7 gote if black answered in the corner. Maybe he would play on the lower side and Iyama didn't want this as he judged that area as more urgent what with there being two big unsettled groups fighting with each other, so moves there could be double sente. But then why didn't white play there instead of the cut? Did Iyama consider Yamashita's cut a mistake and he should punish it as soon as possible before Yamashita has a chance to realise his mistake and play in the more urgent lower side? Was Yamashita's plan in making the cut to then tenuki because he thought it is a good exchange? Why would that be? Afterwards if it is black who comes back to defend there then if he plays b7 then white gets the d6 atari as kikashi and black has to connect at c7, whereas if black defended with b7 and white had't cut then he could hane at d7 which is better. And if black defends with c7 afterwards then white has some aji in b6 he can use with sente moves around b9 or c8 attachment. But the cut also has some minus in terms of losing ko threats and slightly reducing the size of white's yose at the bottom left. So did Yamashita think cut and tenuki was a good exchange?

Thoughts appreciated, particularly if anyone has some pro commentary. Thanks.

Seems to be a problem with Mr Kin's site so here's another link to the game.

http://www.go4go.net/go/games/sgfview/40926

I added a variation the commentator, Uchida Shuhei 7p, gave.
黒１，３はAとカカエてくれない心配をしましたか。

He might have been worried that white wouldn't grab the stone at A.

Oren's idea is nearly certainly the right answer. However, I thunk of something different.

Here's my drunken thought, on a slight tangent:

Click Here To Show Diagram Code

[go]$$cm33 M33 variant
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . 4 . . O . . X . . . . . . . . . . |
$$ | . 2 X . . . . X . . . 5 . . . . . . . |
$$ | . X O O . O X . . . O O X . . X . . . |
$$ | 3 O X O . O X . O , O X X . . , X . . |
$$ | . 1 X . O X X . . . . . . . O . . . . |
$$ | . a . . O . . b . . . . . . . . . . . |
$$ | . . . . 6 . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Even if W plays 36 as shown, as opposed to oren's line, W 38 creates a little mischief. White's move at a next seems to get a ko in the corner, whereas b connects some stuff.

This may be unplayable for white, but the ko makes the analysis unclear to me.

At the end of the game the commentary on wbaduk included this about the position

1がAと取らなかった理由が、まだわかりません。気合、の一言で済ませられることなのかどうか。

"I still don't understand the reason he didn't take at A (B3). Kiai may be the only way to explain it?"

Nice tesuji drmwc, I hadn't seen it. Though if black answers to the right then he could end up killing the stones in sente instead of gote. The ko certainly makes the analysis harder.

From oren's info it seems white was likely to tenuki which means my question of should white have played on the lower side first comes to the fore. And if pros are also puzzled it means there's probably no easy answer; I did wonder if the tenuki was pure bloody-mindedness!

Kiai

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