Under The Stones Sacrifice Shape List

  Difficulty: Intermediate   Keywords: Shape, Tactics

This page is in need of attention.
Reason: lazy page - no surrounding stones offered = easy confusion


Sacrifice shapes which lead to the under the stones tesuji.

Look out for these!

On the edge of the board:

[Diagram]
Bent Four  
[Diagram]
Stupid Four  

Anonymous: A more common name is Squared Four.

[Diagram]
Three plus one  

If the three stones are captured, the one lonely stone can cause a shortage of liberties, which allows under the stones. Example: [ext] http://www.goproblems.com/prob.php3?id=438


In the corner

[Diagram]
Another Bent Three  

Ed? This occurs in the corner

[ext] http://www.goproblems.com/prob.php3?id=2003


In the Center

[Diagram]
Bent Four with a cutting point  

[ext] http://www.goproblems.com/prob.php3?id=4907

[Diagram]
Empty triangle oiotoshi  

Also, a captured empty triangle can cause an under-the-stones-ish capture, but for it to work, black must remove an outside liberty after white captures. This can, however, lead to interesting connection tesujis:

Black can connect even if white captures the 3 stones.

DrStraw: Better for B to play back into the center of the 3 stones than to fill an outside liberty. The effect on B'S shape is the same, but W is not as good.


Shapes that can lead to aforementioned ones:

[Diagram]
Farmer's Hat  

[ext] http://www.goproblems.com/prob.php3?id=3360

unkx80: No, the sacrifice shape in the problem is actually bulky five, a generalization of squared four.

[Diagram]
Bulky five  
[Diagram]
Bent Three  

Kuolema: How does this lead to Under The Stones tesuji? Show me an example.

unkx80: The third one is very rare compared to the first two, but it exists. An example is Under The Stones Problem 8.

("another bent three" diagram moved to "in the corner" section. -bass)

[Diagram]
Bent Five  

[ext] http://www.goproblems.com/prob.php3?id=3748


unkx80: Making a more general statement, I believe the sacrifice stones may be the following shapes, with the optional addition of stones in the x direction or beyond.

[Diagram]
Bent Four  
[Diagram]
Stupid Four  

Bill: The only (non-nakade) example I know of is in the corner, where it is not a question of an eye, but of points.

[Diagram]
Bent three in the corner  

Black picks up 0.5 point.

OC, if we are going to include shapes where the question is points, there is no end. E. g., bent seventeen.

[Diagram]
Bent seventeen  
[Diagram]
Bent seventeen (ii)  

W8 at W3.

This is a 2/3 point Black sente (unless White is komaster, when it is worth 1 2/3 points).



Charles The one time it actually happened to me ...

[Diagram]
Example  

... was when I made the mistake of playing B1 here, thinking it was a snapback .

Bill: I think this is an example of the stupid four (white+circle). It's the sacrificial shape, not the capturing shape, that is in question.

OC, since a nakade can be under the stones, any nakade shape might qualify. <shrug> But we don't usually think of making that shape as tesuji.


Under The Stones Sacrifice Shape List last edited by tapir on July 2, 2013 - 22:26
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