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|Oct-26-12|| ||dufferps: There is so much here that I don't understand. I don't see the purpose in white's 28.Bd4. Apparently the threat of Bxb6, pulling the queen off of c7, was important, because black responds ...Nd7, but maybe there was another reason as well.|
Black resigns after 31.e6, but I don't see how white forces a win after 31 ... Ke7
|Oct-26-12|| ||johnlspouge: < <Conrad93> wrote: Does black have to take the knight? I gave up on the combination after I realized black can just avoid it. >|
<Kotov's Rule>: if you can analyze to a clear P up in all variations, consider the candidate move a win. Typically, a sacrifice presents the defender with a dichotomy: decline or accept. If both cost at least a clear P (as today), Kotov's Rule applies.
Never give up, never surrender :)
[ http://www.youtube.com/watch?v=e-VM... ]
|Oct-26-12|| ||Abdel Irada: <dufferps>: Actually, 28. Bd4 is played to threaten Bc5, cutting off the black king's retreat square. |
And in the game, after the exchange on d5, the bishop enters the attack on g7 via the push 31. e6. (This threat, incidentally, is why some kibitzers preferred to put the black queen on d7 or d8 rather than c7, in order to retain the option of recapturing on d5 with the queen so the pawn advance would be impossible.)
|Oct-26-12|| ||pittpanther: what if black does not take the knight but plays something like 25 f6? it could be hard to extact the knight (and 25 Kxh7 is losing)|
|Oct-26-12|| ||Abdel Irada: <pittpanther: what if black does not take the knight but plays something like 25 f6? it could be hard to extact the knight (and 25 Kxh7 is losing)>|
It is questions like that that make this puzzle far more difficult, as I have said, than many we have seen lately.
|Oct-26-12|| ||David2009: Ribli vs Unzicker, 1995 postscript:
<dufferps: There is so much here that I don't understand. I don't see the purpose in white's 28.Bd4. Apparently the threat of Bxb6, pulling the queen off of c7, was important, because black responds ...Nd7, but maybe there was another reason as well.> The main threat was Bc5 mating.
<Black resigns after 31.e6, but I don't see how white forces a win after 31 ... Ke7>
click for larger view
Neither do I without silicon help! Crafty End Game Trainer finds surprising resources.
Bashing out the win with 32.exd7 Kxd7 33.Qxg7 Qc2! 34.Nxf7 doesn't work: try it!
Crafty EGT link (to play the position interactively): http://www.chessvideos.tv/endgame-t...
An example of over-respectful resignation?
|Oct-26-12|| ||Marmot PFL: <David2009> Then why not just play 33 Bxg7? It's a very easy win for white.|
|Oct-26-12|| ||JG27Pyth: I suspected this puzzle would create controversy -- it's like a hybrid tuesday/sunday! And as such it reminds more of the kinds of actual position problems I encounter in my own games than any other puzzle I've seen on chessgames. Basically, I can see where the early part of an attack might be had but the calculations disappear into a dangerous murk my feeble mind cannot penetrate. The land of the speculative sac. |
Preseneted as a puzzle, here, it's very easy to see that the only immediate sac-attack here is Nxh7, and as has been pointed out it's not even forcing. Black can accept the loss of pawn and decline the knight ... indeed Black should have decline. <whiteshark>:"Unzicker lacks a sense of danger here" -- Maybe, but I highly doubt that -- alarm bells go off even for a C-player when someone sacs a N on h7. Rather, I believe Unzicker simply failed to calculate the ensuing complications correctly. If a +2400 player fails the calculations at the board in a meaningful game I give myself a pass on those calculations too! That's Sunday level stuff for sure. I wonder how far Ribli's calculations went -- post game would he have called this a speculative sac or did he "see it thru" -- My guess is that he saw clearly enough. For a dope like me though and for players quite a few levels above mine -- I think Nxh7 is at least to some degree a speculative sac.
|Oct-26-12|| ||Marmot PFL: All I could see here for white was the typical sacrifice 25 Nxh7. Sometimes white can play this and always has a draw in hand but not here it seems. So 25...Kxk7 26 Ng5+ Kg8 (Kh6 27 Bc1 or Kg6 27 Be4+) 27 Qh5 Qc7 (to escape on e7) 28 Bd4 Nd7 (stops Bc5) and now what? So probably I would not play this but Ribli has the answer, which since there was no draw he must have seen all along.|
|Oct-26-12|| ||kevin86: The knight sac brings in the forces needed for victory.|
|Oct-26-12|| ||BOSTER: The bold white pawn e5 crossed the border and created the pressure on f6 and d6.|
Black pos.is too cramped.
In this pos. where white played 19.Rc4 moving the rook c4 on the same line with queen e2 I'd try 19...Nxe5 and then Bb5.
click for larger view
|Oct-26-12|| ||King Sacrificer: I can't even see the finish if 26...Kh6|
|Oct-26-12|| ||bachbeet: I'm also having a hard time seeing why he resigned because I really don't see a strong continuation for white after black refuses the pawn at e6 and moves the king to e7.|
|Oct-26-12|| ||Patriot: The only candidate I see that "could" lead to a win is 25.Nxh7. However, I'm just not seeing it. White can win a few pawns for the knight and run the king toward the queenside but this does not look promising. One idea I had was to get the dark-square bishop involved with Bd4 at the right moment.|
25.Nxh7 Kxh7 26.Ng5+ Kg8 27.Qh5 Qd7 28.Bd4 Na4 and then what? Or 27...Qc7 28.Bd4 Nd7 and what?
I give up on this...
|Oct-26-12|| ||Phony Benoni: <bachbeet> If Black plays <31...Ke7> in the final position:|
click for larger view
White at the very least can just play 32.exd7 followed by 33.Qxg7, when he is a pawn up and is swarming around Black's king. Perhaps even better is 32.exf7, when White will end up two pawns ahead after 32...Bxf7 33.Qxg7 while maintaining his attack.
Is this a slam-bam-check-check-mate win? Not quite. But if you play around with the position for a few minutes, it quickly becomes hopeless for Black.
|Oct-26-12|| ||Patriot: <<Conrad93>: I guess I was right. The puzzle is far more difficult if black ignores the knight sacrifice.> I think just the opposite--white is a clear pawn up for nothing. I never bother calculating where the sac is declined unless there is another piece hanging or there is some kind of counter-attack. Otherwise you can just say "thanks for the pawn".|
|Oct-26-12|| ||Patriot: It took Houdini over 3 minutes and 21-ply to find 25.Nxh7! I don't feel so bad after all...|
|Oct-26-12|| ||agb2002: The material is equal.
The first move that comes to mind is 25.Nxh7:
A) 25... Kxh7 26.Ng5+
A.1) 26... Kg8 27.Qh5
A.1.a) 27... Qd8 28.Qh7+ Kf8 29.Qh8+ Ke7 30.Qxg7 with two pawns for the knight and many threats (Bh3-Bxe6, h5-h6-h7-h8=Q, Bd4, etc.).
A.1.b) 27... Qd7 28.Bd4 Na4 29.Qh7+ is similar to A.1.a.
A.1.c) 27... Qc7 28.Bd4 Na4 29.Bxd5 exd5 30.e6 looks bad for Black.
A.2) 26... Kg6 27.Qe4+ f5 28.exf6+ Kh5 29.Qh7+ Kg4 30.Bf3#.
A.3) 26... Kh6 27.Qd2 g6 28.Nxe6+ Kh7 29.Ng5+ Kg8 30.Bxd5 Qd7 (pinning the bishop) 31.Bxf7+ Bxf7 32.Qxd7 Nxd7 33.e6 Bxe6 34.Nxe6 + - [2P].
A.4) 26... Kh8 27.Qh5+ and mate in two.
B) 25... f6 26.Qc2 with the idea of trading queens to eliminate a defender of f6, unclear.
In spite of 25... f6, trapping the knight, I think I'd play 25.Nxh7.
|Oct-26-12|| ||Moonwalker: Out of my league! In a real game I'd play 25.Bd4..|
|Oct-26-12|| ||Conrad93: The point, Patriot, is that the task would not be as obvious if black denied the sacrifice.|
By denying the sacrifice, he is forcing white to be more accurate and aggressive.
|Oct-26-12|| ||Patriot: <Conrad93> <The point, Patriot, is that the task would not be as obvious if black denied the sacrifice.> I understand what you're saying and it may even be the best idea for black, but it's a waste of time calculating it from white's perspective. Black is the one that really needs to determine the risk involved in accepting the sac (if white decides to actually take on h7). <agb2002> only points out 25...f6 for the decline, to snag the knight on black's own terms which may have some merit. I don't think there is much else to cause concern though.|
|Oct-27-12|| ||rilkefan: <<King Sacrificer>: I can't even see the finish if 26...Kh6>|
As I noted above, stockfish thinks this is the strongest defense, relatively speaking. I had planned to reply Bc1, but that turns out not to be good after ...g6 (compared to the line below Nxe6 doesn't work since d5 is strong here). Instead sf plays 27.Qd2, with main line ...f5 28.Nxe6+ f4 29.Bxd5 with a complex position though +2 or 27...g6 28.Nxe6+ and ditto.
|Oct-27-12|| ||Conrad93: Patriot, the puzzle would be more difficult and interesting if black denied the sacrifice.|
|Oct-27-12|| ||Abdel Irada: <JG27Pyth>: <<whiteshark>:"Unzicker lacks a sense of danger here" -- Maybe, but I highly doubt that -- alarm bells go off even for a C-player when someone sacs a N on h7.>|
At the risk of misinterpreting <whiteshark>'s comment (and if I have, I'm sure he can correct me): Danger is indeed obvious after the knight sac. What I think <whiteshark> referred to was the preparatory moves, in particular h4, whose purpose is obvious in retrospect and to alert observers: to set up the sacrifice by enabling the second knight to move to g5.
|Oct-29-12|| ||Conrad93: The sacrifice is easy to spot, but the combination is far more difficult to figure out.|
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