Migeru's Question 3

    Keywords: MiddleGame

I lost the game by 30 points, but at some point I made a san-san invasion that would have been worth about that much! Here's what happened

[Diagram]

Failed san-san invasion

Black 4 is the key move.

Zounds! White is dead!

Alternatives:

  • White 9 at a
  • White 7 at a
  • White 5 at 7
  • White 3 at 7
[Diagram]

last-minute fix

Can White live? Can White get seki? Can Black kill?

[Diagram]

White lives

jsha: The obvious variant where Black seals at 1 doesn't work, White simply plays at 2 to make life.

[Diagram]

White runs out the side

If Black pushes at 1 here and White runs, the outcome is complicated, but I think White dies. The follow-up would be something like the diagram below.

[Diagram]

White pushes out further

From here the outcome depends on whether White can make another eye or kill a black group. The former is unlikely; the second may be possible, Black has many weaknesses here.

White 4 looks very slow to me. Why wouldn't it be at 6 or 7? Or even an ogeima up to the third line? I think White should live pretty easily. -- adamzero

[Diagram]

White tries to seal the corner

Instead of running, if White tries to ensure two eyes in the corner with 1, it looks like she wins.

Migeru: The reason is that 3 and a are miai for an eye, and Black can't play at b. In fact, it is not necessary for White to play at b unless Black plays at c.
[Diagram]

White tries to seal the corner 2

jsha: Well, I've had second thoughts on this variation. What about this version?

[Diagram]

White tries to seal the corner 3

Migeru: Yes, how about it? I think a are miai for an eye.

[Diagram]

Next-to-last-minute fix

Ditto?

[Diagram]

Another response to Black 4

With a black stone at b, the status of the white group depends on sente (see L1Group) so one might assume that the extra liberty makes the group alive. However, I am not sure of this. The vital point of the group is at c.

[Diagram]

Shanghai's variation on a theme by Migeru

Black 4 might equally well be played at a.

Shanghai: Actually, Black 4 is better. You could play 4 at a, but if White later plays hane just above 2, the exchange that follows is sente for White. With Black 4 in place, the hane by White just above 2 is gote. This sort of thing matters in a close game.

Also, I can't take credit for the successful 3-3 invasion I suggested - it's a common variation on the best-known one, and was around before I was born. :)


This is a copy of the living page "Migeru's Question 3" at Sensei's Library.
(OC) 2005 the Authors, published under the OpenContent License V1.0.
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