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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.

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.

-- Dieter


Andre Engels: The logic behind this rule is in my opinion 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 2

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.

[Diagram]
Probing cut

On that occasion I think we were discussing this kind of position, in which it is good for Black to cut at B1 before turning at a. W2 is normal since otherwise Black takes the corner. Here of the four possible variations one is 'invisible':


[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).


So in this case it is rather simpler to argue that the proverb gives the correct answer.


Example 3

[Diagram]
On the side

Charles: This is quite a typical kind of position on the side, with WC 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 I think 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.



Discussion

Doug Ridgway: This proverb doesn't make sense to me. If either cut will work, and the opponent can only protect against one of them, then regardless of which side I want, it's the opponent who gets to choose which side I will get. Wouldn't it be better to cut on the side that the opponent will end up giving me anyway? That way, the opponent doesn't get to capture a stone, which is better for them than for me.

[Diagram]
Better for Black

In the original example, if White wants the outside, then isn't this better for Black than the original?


[Diagram]
Bad for Black

Or alternatively, tewari-style, the B3 - W4 exchange is obviously bad for black. (I hope this isn't Lying With Tewari.)


Andre Engels: Yes the diagram "Better for Black" is, and that is exactly what the proverb is about: If White is going to take the outside anyway, then apparently the outside is more important than the inside, so it is the side that you want. And if you want the outside, the proverb tells you to cut on the inside - which is exactly what you are doing here.

Charles: You have to look at the line where White resists Black's chosen plan:

[Diagram]
White doesn't capture

Here White should be in trouble, because the corner is just about to die. White denies Black the corner, indeed; but the cost is too high even if the ladder for Black to capture WC is bad.

Doug Ridgway: I agree, so White won't do that, and will let Black have the corner if Black cuts on the outside. But would White take the corner if Black cuts on the inside?


[Diagram]
Black cuts inside, White wants the corner

It's easier for White to live now, and the outside stone isn't dead yet, so maybe White would do this. If so, then maybe the original cut on the outside is correct, as a sacrifice to convince White to give Black the corner. Otherwise, if Black gets the corner in any case, it seems to me that the original cut on the outside is a One-Two-Three mistake.

Charles: This is (perhaps obsolescent) joseki, but only if Black has a good ladder at a to capture: B5 here isn't adequate.

Doug Ridgway:


[Diagram]
3-3 invasion of 5-3

If it's joseki, then it's OK, so let's look at joseki.

The original position can arise from 3-5 point 3-3 approach when Black attaches at B3. Kogo states that Black needs the ladder even before attaching at 3. With no ladder, the best he can do is cut at a and take the corner, but the result favors White (according to Kogo). With the ladder, he cuts at b and takes the outside. What I find interesting is that the paths with White connecting don't even appear -- as far as the joseki book is concerned, White will always capture, never connect.[2] (If I did the search right.)

Gobase can find only one of these joseki actually played: the inside cut followed by the ladder, and in only one game. Most popular is Black a White c Black d, and Black a White b has also been played. Maybe this is an example of there's no such thing as joseki?.

Andre Engels: I am a bit at a loss at what you're saying. What do you mean by 'these joseki' when you say that Gobase can only find one of these joseki actually being played? Anyway, my own joseki database (consisting of MasterGo's database plus games downloaded from the Internet plus games typed in by me from magazines, totalling slightly over 20,000), I find the following variations:

  • Black cuts on the outside, White captures, Black takes the corner (a-c-b) 42 times;
  • Black cuts on the outside, White captures, Black gives atari from above (a-c-d) 4 times;
  • Black cuts on the inside, White captures, Black sets up the ladder 9 times;
  • Black cuts on neither side, but plays at d immediately, 2 times.

[Diagram]
9 by 9

Here's another example, a position which occurred in one of my games. Suppose White decides to cut: a or b? I think Black will connect on the bottom, regardless of which side White starts on: it's easier to live, and there's more White territory to threaten. So White should cut at a, as this is the side that Black will give up. White a, Black b, White c is what I would expect. Does this make sense?

Charles: Given your hypothesis about Black's intention, yes, it makes sense.

Dieter: If you capture the cutting stone, it will be easier to live regardless of the surroundings. There are of course occasions on which Black will not capture the cutting stone, because giving White what she wants more than offsets the advantage of capturing the cutting stone. In your example however, that is not the case. I will capture the cutting stone without even thinking.



[1]: Let me reformulate André's correct explanation:

If Black cuts the side he doesn't want, White is faced with either capture the cutting stone AND give Black what he wants or not capture the cutting stone AND give Black what he doesn' want.

If Black cuts the side he wants, White can either capture the cutting stone AND give Black what he doesn't want or not capture the cutting stone AND give Black what he wants.

The latter is something like either work and get no money or not work and get money, hardly a difficult choice.

-- Dieter


[2]: Charles: This sort of lacuna in joseki books, where they don't explain or indicate the most fundamental points, is very typical: too much of the wrong type of data for some users.



This is a copy of the living page "Cut the side you don't want" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.