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 a tempo, shortage of liberties. But everything requires exact reading.
HolIgor: Black can do better.
I'm not sure of the best 'defence' for White, but I cannot see any quick way for White to save his stones after ...?
White rebuts this with a simple outside attack true to the fundamentals. HolIgor
Oops. I thought Black could cut one to the left of , 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.
Before HolIgor does so, allow me to make a try... After , White clearly is one move behind.
A better defense for White seems to be here. After White 12, Black loses despite the me ari me nashi.
Black however has an improvement with here. First destroying the eye, then moving out seems to be enough to save Black.
One more line of defense seems open for White, namely here. But the - exchange again saves the day. If White plays Wh6 at a, Black plays at , and gains liberties again.
I hate disagreeing with stronger players, but how does Black play after 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.
Yes, Black sacrifices two stones but kills the rest. --HolIgor
Thus the first move is found:
White's strongest defence is . So the problem is to find Black's second move; which is the key, as Dave put it.
Yes, this is the solution. The variations should be considered further:
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?
Apparently, 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.