Cut the side you don't want

    Keywords: Tactics, Proverb

Because the enemy must normally capture the cutting stones, one should cut the side one doesn't want.

The logic behind the reasoning is the following: after you cut, your opponent can still choose either side.

  • if he captures the cutting stone, he takes the side where you cut
  • if he covers the other cutting point, he takes the side where you did not cut.

Capturing the cutting stone gives the opponent a much better shape (ponnuki), and is therefore preferred by him. If you would cut at the direction where you want to play, he can take both advantages (getting the ponnuki and getting the best side), if you cut at the direction where you do not want to play, he will have to choose. [1]

Example 1

[Diagram]
Black wants the corner  

If Black wants the corner, he should cut at a.

[Diagram]
Black gets the corner  

White captures the cutting stone, and Black gets what he wants.

[Diagram]
Black wants the outside  

If Black wants the outside, he cuts at B1. We assume the ladder works.



In neither of the above variations can White afford not to capture the cutting stone.

Example 2

[Diagram]
Probing cut  

In this position it is good for Black to cut at B1 before turning at a. W2 is normal since otherwise Black takes the corner.

[Diagram]
Irrational for White  

White really can't play W2 here: a novice's mistake. White should play b, naturally, to keep the corner. Therefore B1 here is the wrong side to cut, because the sequence B1, White b, Black at W2, White captures is worse than the previous diagram (a One-Two-Three mistake by Black).


Example 3

[Diagram]
On the side  

This is quite a typical kind of position on the side, with white+circle jumping out past the black stone.

[Diagram]
Attacking White's shape  

Now after B1, playing at B3 is the correct idea for Black. Probably White has nothing better than W4, in which case B5 and W6 make sure White has no eye shape here. Black can continue to attack White's group.

[Diagram]
Wrong idea  

It would be a bad idea to follow Example 1 in this case, by cutting with B1 here. White would be very happy with the ponnuki W4, and Black cannot even cut White on the left.

[Diagram]
What Black 'wants'  

In this position you can say that Black wants this outcome, where White decides to capture B1 with W2, and B3 and B5 (or a) are on the side Black 'wants'. That is, Black's fundamental desire is to cut White's long jump along the third line successfully with B3.


See /discussion

[1]: Charles: I can remember discussing this kind of point in general with Tim Hunt. Usually there are four variations like A, A', B, B' where it is easy to see that you prefer A to A' and B to B'. On the other hand your opponent will have the choice of giving you a result out of A or B', or out of B or A'. Somehow the decision is between a worse form of a better result, or a better form of a worse result? But actually this is probably just a basic game theory pattern being applied here.


Cut the side you don't want last edited by 24.91.93.132 on November 17, 2014 - 19:50
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