You know the fights that you "should" win? The ones where your opponent cuts you and your group will have an extra liberty over the cutting group, so you should theoretically be able to capture the cutting stone? Whenever I get into those situations, somehow they manage to wiggle and get extra liberties and then I'm in a fight where I'm losing. It's incredibly frustrating, and it's a blind spot in my play that I can't figure out.

So here's a situation that came up recently. It's black move (me) and I really want to double hane. But part of the analysis of whether I can afford to do so depends on what happens if the opponent cuts at e17.

Click Here To Show Diagram Code

[go]$$Bc Black to double hane and risk a cut
$$ ------------------
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . X X X . . . . .
$$ | . O O O X . . . .
$$ | . . . . O . . . .
$$ | . . . . . . . . .
$$ | . . . O . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$[/go]

Black double hanes, white cuts at e17. Black connects and white extends. So we end up with this:

Click Here To Show Diagram Code

[go]$$Bc
$$ ------------------
$$ | . . . . . . . . .
$$ | . . . . O . . . .
$$ | . X X X O . . . .
$$ | . O O O X X . . .
$$ | . . . . O X . . .
$$ | . . . . . . . . .
$$ | . . . O . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$[/go]

It's black to move and both of his groups have four liberties, and so does the cutting group. But with black to play first, theoretically, he should be fine here, right?

What's the best move here to win the fight? This seems like a basic thing I should know, but I always mess this up. Can someone give me some pointers?

Or am I wrong, and is white fine here?

Well, just because you have 4 liberties and so does he doesn't mean you should win the fight. It depends if groups can run away to get more liberties, special things at the edge/corner of the board, approach moves and so on. The way I would approach this situation is:
1) Black outside group is not going to die any time soon.
2) Black corner group is surrounded and might die.
So what happens if black helps the weaker group and takes a liberty?

Click Here To Show Diagram Code

[go]$$Bc
$$ ------------------
$$ | . . . . . . . . .
$$ | . . . 1 O . . . .
$$ | . X X X O . 2 . .
$$ | . O O O X X . . .
$$ | . . . . O X . . .
$$ | . . . . . . . . .
$$ | . . . O . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$[/go]

White runs away and isn't surrounded, black fails. I also see that this corner shape is an L group and I know they are dead.

So next I try block from the other side (obviously f18 doesn't work as he can push through and capture) and read what happens if white pushes into the corner. After 3 both have 3 liberties (thanks to black making an empty triangle) but now it's whites turn! Sometimes 4 is a tesuji but black can just take libs and win:

Click Here To Show Diagram Code

[go]$$Bc
$$ ------------------
$$ | . 4 6 7 8 9 . . .
$$ | . . 3 2 O 5 . . .
$$ | . X X X O 1 . . .
$$ | . O O O X X . . .
$$ | . . . . O X . . .
$$ | . . . . . . . . .
$$ | . . . O . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$[/go]

But how about 4 here to take a lib? Looks like black dies if he blocks and goes straight for liberty racing (but what about 9 at b15 escape?!).

Click Here To Show Diagram Code

[go]$$Bc
$$ ------------------
$$ | . 8 6 . . . . . .
$$ | 5 0 3 2 O 9 . . .
$$ | 4 X X X O 1 . . .
$$ | 7 O O O X X . . .
$$ | . . . . O X . . .
$$ | . . . . . . . . .
$$ | . . . O . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$[/go]

So next I read what if black takes the key point looking descent. The value of this is white taking the liberty at d19 makes his own empty triangle.

Click Here To Show Diagram Code

[go]$$Bc
$$ ------------------
$$ | . 6 5 . . . . . .
$$ | 7 . 3 2 O 9 . . .
$$ | 4 X X X O 1 . . .
$$ | 8 O O O X X . . .
$$ | . . . . O X . . .
$$ | . . . . . . . . .
$$ | . . . O . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$[/go]

And tada! Even though after 9 both have 2 liberties and it is white to play, white can't approach black so black wins. So this would be my tentative conclusion, that black can win this way. I would then read more to check if I had missed any variations. For example as 5 was black's key point, what it white plays 4 there? He can't connect but maybe some ko? It's far more complicated than 4 = 4 => sente wins, we can see in the intermediate position it was 3 vs 3 with white sente. But 4 vs 4 with sente certainly gives us hope that it's plausible black could win.

Edit: almost forgot to say, you need to read this too, it's a bad shape for white that can run out of libs and gives black forcing moves to help the L group live, but still need to check.

Click Here To Show Diagram Code

[go]$$Bc
$$ ------------------
$$ | . . . . . . . . .
$$ | . . . . O . 2 . .
$$ | . X X X O 1 . .
$$ | . O O O X X . . .
$$ | . . . . O X . . .
$$ | . . . . . . . . .
$$ | . . . O . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$[/go]

And in this situation the outside group has enough libs you don't even need the ladder, but sometimes this can be a problem:

Click Here To Show Diagram Code

[go]$$Bc
$$ ------------------
$$ | . . . . . . . . .
$$ | . . . . O 2 3 . .
$$ | . X X X O 1 4 . .
$$ | . O O O X X . . .
$$ | . . . . O X . . .
$$ | . . . . . . . . .
$$ | . . . O . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$[/go]

So what I'm taking away from all of that is that I shouldn't double hane. LOL!

Not really. All you can generalize from this is that you shouldn't double hane without looking.

A double hane is often a strong move. However, it may not work in situations where you have an unprotected weakness and he doesn't.

In the particular situation, you might do well to observe that you have a weakness, and ask yourself what you can do to protect it, and if that protecting move has other benefits.
In other words, maybe you should not make the decision to fight.



You don't have to fight here. The extension below covers the weak point and starts making fourth rank territory.

Click Here To Show Diagram Code

[go]$$Bc
$$ ------------------
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . X X X . . . . .
$$ | . O O O X 1 . . .
$$ | . . . . O . . . .
$$ | . . . . . . . . .
$$ | . . . O . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$[/go]

_________________
Help make L19 more organized. Make an index: https://lifein19x19.com/viewtopic.php?f=14&t=5207

Thunked, this was the exact position in a go tesuji app.
Just to copy: the tesuji it proposed was to just connect at e17.

Remember the proverb: strange things happen in the corner. It is not only about liberties. And even if you can make it live, you may also want to ask yourself if it is best result if you lose sente when you have to make it live, and/or if you lose extension/connection towards the center.

I was trying to jokingly say that it was beyond my skill to read out all your variations, and thus, I couldn't safely hane.

That makes a lot of sense. Even if I survive the fight, the opponent is probably going to get more compensation out of harassing me and forcing me to kill those stones than I'm going to get from the hane.

And that counting liberties for groups which aren't surrounded isn't so useful.


What?! Extend to f16 is better. Extending on the 4th line like that is a good result for black. Whether black can double hane and get an even better result requires more reading and judgement.

This continues like this:

Click Here To Show Diagram Code

[go]$$Bc
$$ ------------------
$$ | . . . . 6 4 . . .
$$ | . . . 5 O 3 2 . .
$$ | . X X X O 1 . .
$$ | . O O O X X . . .
$$ | . . . . O X . . .
$$ | . . . . . . . . .
$$ | . . . O . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$[/go]

...and ends up looking strangely familiar:

Click Here To Show Diagram Code

[go]$$Bc
$$ ------------------
$$ | . . . 1 O O 2 . . . .
$$ | . . . X O X O . 4 . .
$$ | . X X X O X . 3 . . .
$$ | . O O O X X . . . . .
$$ | . . . . O X . . . . .
$$ | . . . . . . . . . . .
$$ | . . . O . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$[/go]

...and it repeats:

Click Here To Show Diagram Code

[go]$$Bc
$$ ------------------
$$ | . . . 1 O O 2 6 8 . .
$$ | . . . X O X O 5 4 . 0
$$ | . X X X O X 7 3 . 9 .
$$ | . O O O X X . . . . .
$$ | . . . . O X . . . . .
$$ | . . . . . . . . . . .
$$ | . . . O . . . . . . .
$$ | . . . . . . . . . . .
$$ | . . . . . . . . . . .
$$[/go]

This is logically similar to a ladder in that it depends upon running into the opposite edge of the board, or other stones.

( BTW, is there a proper name for this? If not, I hereby christen it "Joaz's great plastering" )

_________________
Help make L19 more organized. Make an index: https://lifein19x19.com/viewtopic.php?f=14&t=5207

Click Here To Show Diagram Code

[go]$$Bc
$$ ------------------
$$ | . . . . 6 4 . . .
$$ | . . . 5 O 3 2 8 .
$$ | . X X X O 1 7 . 9
$$ | . O O O X X . . .
$$ | . . . . O X . . .
$$ | . . . . . . . . .
$$ | . . . O . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$[/go]

7 is the tesuji in this situation.

@OP: Winning fights that you should win is really hard, because you need to think about all of these variations and know all of these tesujis beforehand. Of course, that means that you can simply start fights that you shouldn't win, and come out ahead anyway...

Yes, there is a proper name for it .... I hope! I would hate to have to spend the rest of my life naming it as you just did.

I supposed the good thing is that most people see it in advance so that it does not actually need to be played out.

_________________
Still officially AGA 5d but I play so irregularly these days that I am probably only 3d or 4d over the board (but hopefully still 5d in terms of knowledge, theory and the ability to contribute).

In another thread I recently suggested Fedya (6 kyu) do the GoGameGuru intermediate problems as they featured useful real game situations. Shaddy's tesuji is an example.