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JBS Solution
    Keywords: Problem

[Diagram]
Diag.: Black to play.

Post your solution here.



HolIgor: I won't post a solution yet. In fact I am amazed at the level of this problem. Could it be dan level? We have not heard from our dans yet.

I lost it in an IGS game. I agreed gladly to this position considering it a sure win for Black. But it proved to be much more difficult than expected. So, I decided that Black loses here.

- Perhaps I should have added I'm a European 2 dan. Goran

When I opened a book at a random diagram I could not believe my eyes. Is it possible for Black to win?

Some general words about the solution. The motifs are normal: a group with an eye wins agains a group without eyes, hence some eye stealing, a sacrifice to gain tempo, damezumari, of course. But everything requires exact reading.


[Diagram]
Diag.: How about a ko (9 at 1)... Goran

HolIgor: Black can do better.


[Diagram]
Diag.: Black 1? MortenPahle

I'm not sure of the best 'defence' for White, but I cannot see any quick way for White to save his stones after Black 1. ..?


[Diagram]
Diag.: Black 1 fails

White rebuts this with a simple outside attack true to the fundamentals. HolIgor

Oops. I thought Black could cut one to the left of 6, but he cannot.:-(



DaveSigaty: I couldn't figure this one out. Finally I gave up and searched my books for an analysis - I wasn't even close to finding the key play (which is Black's second play rather than his first!). The honor of posting the answer belongs to HolIgor when he is ready.


[Diagram]
Diag.: My attempt

Before HolIgor does so, allow me to make a try... After Black 7, White clearly is one move behind.


[Diagram]
Diag.: Better defense (Black 11 at 'a', White 12 at 'b')

A better defense for White seems to be White 2 here. After White 12, Black loses despite the Me Ari Me Nashi.


[Diagram]
Diag.: Improvement

Black however has an improvement with Black 7 here. First destroying the eye, then moving out seems to be enough to save Black.


[Diagram]
Diag.: No good either

Playing White 6 on this side does not work either. After Black 7, the best White can get is to capture Black 5 in sente.


[Diagram]
Diag.: Last defense?

One more line of defense seems open for White, namely White 4 here. But the Black 5 - White 6 exchange again saves the day. If White plays White 6 at a, Black plays at 6, and grabs liberties again.

-- AndreEngels


[Diagram]
Diag.: White's defense?

I hate disagreeing with stronger players, but how does Black play after White 6 here? Black must defend against White a. Black at b gives White d and Black dies.

Black at a gives White c and Black dies. Black at e again gives White c and Black suffers? -- MortenPahle

You should not hate disagreeing with me. Certainly not when, as in this case, you are right and I am wrong. -- AndreEngels

HolIgor: The move proposed by Morten is a strong defence but Cho shows how to beat it. Consider it a new problem.


[Diagram]
Diag.: Black wins still!

[Diagram]
Diag.: Black 'e', White 'c' Black 3? Goran

Yes, Black sacrifices two stones but kills the rest. --HolIgor



Thus the first move is found:

[Diagram]
Diag.: Black 1 is the first move.

White's strongest defence is 2. So the problem is to find Black's second move which is the key as Dave put it.

-- HolIgor



[Diagram]
Diag.: Black 1 seems to work. Goran

Yes, this is the solution. The variations should be considered further:

JBS final solution.



[Diagram]
Diag.: Alternative solution?

dnerra: I just looked at this problem and read out this simple-minded sequence. It looks so obvious that it might be worth discussing: What did I miss in this sequence?


[Diagram]
Diag.: Tesuji

Apparently, White 1 in this diagram is the only move here. (White a, Black b, White 1, Black c should usually be very good for Black, as White has to come back and make life at d.



HolIgor

[Diagram]
Diag.: Tesuji

The usual tesuji in such cases is this White 1. I give only one variation. But one has to be very careful. The problem is very good. It was published more than a half millenium ago.



This is a copy of the living page "JBS Solution" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.