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John Nunn vs Slaheddine Hmadi
World Team-ch 1st (1985), Lucerne SUI, rd 1, Nov-16
Sicilian Defense: Najdorf Variation. English Attack (B90)  ·  1-0

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Dec-13-07  UdayanOwen: MostlyAverageJoe -- how are you going? nice to get a reply to my post....

I think the reasons why its not practical to bother calculating every possible attempt to defend after refusing the Bishop sac, is because there are many possible lines, yet none of them change the fundamental strategical character of a position in which white has black completely on the ropes.

I think you might be caught up a little too much in thinking that chess decisions can only be correctly made on the basis of exhaustive concrete variations. It is really important to understand positions not just in terms of variations but in terms of words that knit together the strategical factors in the position and help you make an assessment of a position... after all, not even the strongest computer program can calculate forever in a typical middlegame position, so we all have to be able to make stop analyzing and make conclusions when it is practical to do so.

An analysis of the strategical factors in the position before Bh6 reveals that black is getting crushed positionally, due to the poorly defended kingside, the target on h6, the weak pawns on d6 and a6, the hole on b6, the underdeveloped black pieces, the space advantage for white, and the incredibly active and well co-ordinated white pieces.

The move Bh6 is strategically logical in that it exploits one of black's weaknesses. It works tactically, so it wins a clear pawn (which is an improvement in anyone's books); but even more importantly, it dramatically improves the position, since now the 3rd rank is cleared for the rook to join the attack, and strong pressure is being placed on g7, soon to be supported by the rook. Meanwhile, black's underdeveloped, cramped and unco-ordinated pieces are always likely to struggle to get to the black king as quickly as the well developed and co-ordinated white pieces that have space to maneuver.

This is more than you can ask from a single chess move... it works tactically to win material, fits logically with the strategical essence of the position, and strongly furthers our natural strategical plan. You can calculate how to deal with black's defence when he plays it, because niether your positional nor your material advantages are going to disappear in a hurry, and if they do, it will be due to inaccuracies that follow the move 21.Bh6.

My friend and coaching colleague, GM Darryl Johansen, once taught me that strong players don't differ dramatically from weaker players in the number of variations they look at... The most significant difference is the ability to use intuition and positional judgement to choose the lines that count, and to be able to make sound practical judgements about when one can stop analyzing because the move they want to play just works. If GM's get to use such shortcuts when they are appropriate, then why can't we mortals say, I've won a pawn based on a long calculation of mate, retained all my positional advantages, and furthered my attack in a logical way that is in harmony with the needs of the position.... puzzle solved!

I had to separate my post into two due to its length (that's not like me to crap on.....) so see next for more......

Dec-13-07  UdayanOwen: Continued from my previous post:

The only thing that could be wrong with Bh6 is not that black has some miraculous defensive procedure that cures black's positional problems, safeguards the black king, nullifies white's positional advantages, and wins back the pawn (all these would have to be achieved to prevent white retaining the advantage, and if one doesn't have the positional judgement to appreciate this is not going to happen here, they would be better served developing this judgement than trying to become a stronger calculating machine)... The only thing that could be wrong with Bh6 in a position like this is that there is something better!!!

Granted that there are situations in chess games where deeper concrete analysis is required, but this is in more complex positions where one side does not have such extreme positional dominance, and in particular, where the defender has some kind of positive imbalance that can be used to exploit a weakness(es) in the attacker's camp. Black has nothing positive to work with, and the only potential weaknesses for white are the pawns on a5 and e5.... However, black cannot go fishing for these since his king will be executed.... in the meantime, if black does manage to pull a reasonable defence together around his king (which is a bit of a fairy tale, but lets say hypothetically he does), then white can say, allright, I've got you tied up here now, and I've already cashed in for a pawn from that kingside expedition, now I will tack back to the queenside where I am positionally superior and try to gobble up some more stuff...and even if I can't, I've got a pawn and I can go into the endgame with the advantage.

Anyway, I really should LET GO of my favourite game and go to bed now, since 5:30am is pretty late (or early....)

Take care :-)

Dec-13-07  UdayanOwen: A beautiful game by Nunn
Dec-13-07  MostlyAverageJoe: <UdayanOwen> I appreciate your explanation, but still disagree that the winning advantage after the sac refusal is obvious, for one simple reason: the black player kept playing instead of resigning on the spot.

A look at the records of both players in 1985 shows:

Hmadi: rating 2397

Nunn: rating 2712

If the losing situation is indeed so obvious, why would Hmadi keep playing against a much higher-rated opponent (who was at the time #12 in the world). OK, so Nunn did not do well in that tournament (2568 performance), but still, if the white's advantage is so obvious, why suffer? I've seen games resigned when the computer-calculated advantage is less than what you see in this game.

Bottom line: if the positional imbalance was not obvious to a ~2400 player, I am not convinced that easily, either :-)

Source for the rating info: http://db.chessmetrics.com/CM2/Find...

Dec-13-07  DukeAlba: <UdayanOwen> Great posts, very informing.

I agree with what you said.. After a while you can't follow a line too deeply because it's almost impossible to be able to calculate all the different variations that can arise from a move...

Dec-13-07  MostlyAverageJoe: <DukeAlba> & <UdayanOwen> Just to make clear: this particular statement, along with the one I already quoted previously, is what I disagree with:

<UdayanOwen If black doesn't take the bishop offer on h6 then white is a pawn up but more to the point, with a clearly winning attack, no further analysis needed.>

Noting that another likely winning line starts with 21.Nb6, I am convinced that SOME additional analysis is needed to ascertain the superiority of 21.Bh6.

My attempt to solve the puzzle (within the 4-minute time limit I set for myself on Thursdays) boiled down to "ok, if black takes, then he gets mated, otherwise we have a pawn and there seem to be no counterattack, good enough." Personally, I am not satisfied with this, and don't consider it to be fully valid solution.

Dec-13-07  DukeAlba: <MostlyaverageJoe> I see... Yes I see what you mean.
Dec-13-07  DukeAlba: <MostlyAverageJoe> I guess all I can say to the post about why Hmadi didn't resign to Nunn even in the position he was in, is that no one ever won by resigning. Maybe Hmadi hoped that Nunn would make a mistake...

I guess he had nothing to lose.. looks like the only explanation besides the one you put up which would also be good.

Dec-13-07
Premium Chessgames Member
  Jimfromprovidence: <udayanOwen><In regard to the discussion that black made an error the move before the puzzle, I think it is more accurate to suggest that black has wandered into a disastrous position where white has complete positional domination. If, as Jimfromprovidence suggests, 20...Nf6 is the way out, then the surrender of the pawn clearly indicates the errors preceded move 20....>

Your analysis completely overstates white’s advantage at move 20. Black got into some very minor difficulty when he decided to get greedy playing 15… Qxe2 instead of developing his game with something like 15… Nd7. At move 20, with Nf6, black is still in pretty good shape.

Sure, white can take the d pawn, but white’s d pawn is also vulnerable.

I bet that the position after 20… Nf6 calculates to less than a pawn advantage for white.

It's simply wrong to assume that white will cruise to an easy victory given this position.

Dec-13-07
Premium Chessgames Member
  johnlspouge: Once, I believed that to sacrifice, you had to calculate every line completely, but Rudolf Spielmann's "The Art of Sacrifice in Chess" taught me otherwise. A demand for complete calculation eliminates too many superlative moves from consideration. Judgment about positional compensation for material comes with experience and eliminates some of the need for exact calculation. Sometimes, however, there are critical lines in a sacrifice, giving rise to positions not compensating for material. Those lines need to be calculated to tactical resolution in a superior position, otherwise the sacrifice is speculative, and an act of hope, not skill.

As a consequence, stronger players tend to produce shorter analyses, because they consider some positions as "obviously" won, while weaker players still require further tactical analysis as proof.

My analyses, e.g., are still much longer than <dzechiel>'s ;>)

Dec-13-07  DukeAlba: <johnlspouge> Good observation. I guess it also comes down to judgement. Just like yesterday's puzzle in which white won when black fell into a trap.

Some people saw the move immediately while others reasoned that black would not fall for the trap. I was one who saw the trap but was suspicious about whether or not black would fall for it... although some people did mention that the second best move could transpose into the one made to set up the trap.

I agree... And I also say that sometimes the best move turns into the worst when black responds in an uncharacteristic way (although I don't think its the case with today's game)

Dec-13-07  newzild: I must say that I completely agree with UdayanOwen.
This is a situation where the player sees Bxh6, notes that there is a mating attack if the pawn is taken, and does not really have to calculate further because simply retreating the bishop on the following move gives white an extra pawn with the better position. I doubt Nunn calculated all the lines before playing the sac. He probably just saw that White had a raging attack, and experience told him that there was a win there somewhere. This is a thought process employed by virtually all top Grandmasters. Another technique many Grandmasters use is to see whether a complicated sac will produce a forced draw. Then they play the sac - and look for something better, safe in the knowledge they have a "safety net" to bail out.
Dec-13-07  MostlyAverageJoe: <newzild: I must say that I completely agree with UdayanOwen. This is a situation where the player sees Bxh6, notes that there is a mating attack if the pawn is taken, and does not really have to calculate further because simply retreating the bishop on the following move gives white an extra pawn with the better position>

Ah, but this is exactly what I did, and still I am not happy. Maybe I am too hard on myself.

On the other hand, <UdayanOwen> said something different; he said nothing about retreating the bishop, but asserted that white has a clearly winning attack that requires no analysis. Why would that attack be preferable to 21.Nb6, which most likely also wins?

If we were all GMs here, this argument might be acceptable, but AFAIK most are not, so observation of <Johnlspouge: ... weaker players still require further tactical analysis as proof.> holds.

All this said, I hope that <UdayanOwen> will become a regular contributor, since I really appreciate his insights; they remind me of some of Silman's writings about a need to assess positional imbalances when approaching any given position and then find a way to exploit them. I just wish I were able to do such analysis reliably.

Dec-13-07  patzer2: For today's somewhat difficult Thursday puzzle solution, the demolition combination 21. Bxh6!! does the trick.
Dec-13-07  mworld: i solved all the continuations in the bishop decline variation EXCEPT I never even thought of f6 - i'll give myself partial credit though, since the f6 variation is easy enough to deal with.
Dec-13-07  MostlyAverageJoe: Factoid of the day:

The number of kibitzes on CG that contain the word "demolition": 544 (including this one).

The number of those kibitzes that were written by <patzer2>: 280

MAJ the statistician

Dec-13-07  JG27Pyth: <M-A-Joe: "ok, if black takes, then he gets mated, otherwise we have a pawn and there seem to be no counterattack, good enough." Personally, I am not satisfied with this, and don't consider it to be fully valid solution.>

That's _exactly_ what I arrived at as well. I gave myself 80% credit (*generous, non?) In any sac situation you've got to consider the line if declined. (And if the sac is well calculated, it *should* be declined, shouldn't it?) I looked for a counterattack, which is just plain old chess due dilligence, but I failed to identify black's best defense (f5) and moreover failed to calculate the Bxg7 sac. I think full credit goes to anyone who calculated Bxg7 as a plausible continuation.

Pyth

Dec-13-07  UdayanOwen: Hi all,

Can I say firstly how pleased I am that my post has stimulated such lively debate....

Jimfromprovidence -- If I have completely overstated white's advantage at move 20, I might be guilty of some bias... These kinds of positions, where one has space and co-ordinated piece play, against a disorganised and cramped enemy with several weaknesses are my absolute favourite to play - I find them very dreamy....

I don't have a lot of time to analyse the move 20...Nf6, since after my marathon session til sunrise, I have woken late and have to study today.... But superficially, it looks definitely like black's best chance for counterplay so hats off for the suggestion. In fact, after some brief analysis, I completely agree with you that 20...Nf6 is way better than 20...Bc7...

If white takes on d6, black can get the d pawn back quickly, and It frees up black's pieces and complicates the issue. On the other hand, 20...Bc7 defends d6 but allows white a free reign to win a pawn and exploit his positional superiority with either 21.Bxh6 or 21.Nb6. After 20...Nf6, if black takes on d6, black can get the d pawn back quickly, and blacks pieces are freer and he is complicating the issue:

20...Nf6 21.Nxd6 and now:

21...Qc7 I think is inferior, allowing 22.Nf5 Nxd5, when white's attack still looks extremely yummy (but black is not down a pawn this time and has better defensive and counterattacking chances than in the game).

21...Qd7, keeping the knight out of f5, seems to give black even better chances. 22.Nc4 Qxd5 (pinning the knight and thus preventing Nb6) and black seems to be getting very comfortable, with centralised pieces, material equality, the bishop coming out and the rooks having files.... After 21...Qd7, intuitively 22.Bc4 Nxd5 seems to still give white excellent play, but black is fighting here... I'm not going to analyze this position now, not yet at least, because there is a way to control the position after 20...Nf6 that should now be analysed because I suspect it will lead to a pretty cruisy queenside attack without much black counterplay...

Lets check it out... 20...Nf6, and I see three options to try and maintain a grip on the position:

21.Nb6 Bxb6 22.Rb6 (22.axb6 Qb7 looks OK for black) Nxd5 Rc1, when white will pick up the a pawn... he seems to have the edge but this seems playable for black

21.Qd3. or 21.Rd1. The idea is to control the position and create sustained play against black's queen side weaknesses (a6, d6 and the holes on b6 and c6), but admittedly, he will be slowed by the duty of holding his own d5 pawn... there are several options for black, and I don't have time to analyse them properly... I intend most likely to play Nb6, and if black plays Bxb6, to recapture with the rook, pressuring both a6 and d6... hopefully then I can maneuver a piece to c6 to increase the pressure... Strategically after either of these moves to defend the d pawn, white has a clear edge, and my analysis so far of various options by black all retain that clear edge with pressure that will be extremely hard to shake.... I still think the position is pretty dreamy, but I can't find a cruncher and black is hanging on for the moment (unlike in the game).

Well done for coming up with 20...Nf6.... Not only does it seem to retain material equality and create strong counterplay in many lines, but in the lines after 21.Qd3 or 21.Rd1, white has been slowed down and his play seems more limited to the queenside now. What I like about this move is its logic... In the puzzle position, black has so many problems that passive defence is sure to fail... 20...Nf6 centralises, gives the king a defender, and attacks white's only real target in this position, the d5 pawn.

Chess rocks!

Dec-13-07
Premium Chessgames Member
  al wazir: <RandomVisitor: After 21.Rc1> Thanks. I never considered 22. Nb6.
Dec-13-07  GannonKnight: Good analysis. I did select 21. Bh6, but I feel better that I was unable to devise a forced winning plan. It just seemed like the move that was going to destroy a poorly defended king-side.
Dec-13-07  apple pi: <MostlyAverageJoe>
How did you get that stat?!
Dec-13-07  MostlyAverageJoe: <apple pi: <MostlyAverageJoe> How did you get that stat?!>

Go here: http://db.chessmetrics.com/CM2/Find...

Click on Hm

Click on Hmadi

Click "Event details"

Search for "Luzern" (Hmadi's ELO is right next to it).

Repeat the above for Nunn, or click on Luzern and look him up in the resulting page.

Dec-14-07  jperr75108: nice problem.
Dec-14-07  UdayanOwen: Okay, so on the issue of whether one needs to calculate further if black doesn't take the bishop....

I think there are two ways to classify a position as winning.... A strategically winning position, and one in which there is an absolutely forced sequence that leads to devastating material gain or checkmate. Obviously the second is better... Whites position is strategically winning after Bxh6, but there is no clear cut forcing win... But Nunn played it, and he analyzes the @#$% out of his games in post-mortem and this game has since been immortalized as a tactics puzzle... If a weakness in white's plan was found, I'm guessing it wouldn't make it as a puzzle, so lets assume it was the best move in the position... How can the puzzle not be solved after finding Bh6, but not the final position, when that final position was not completely forced? Or put another way, if Bxh6 is the best move, it has to be played on strategical grounds because there is no forcing win.... Who said a puzzle has to have a forcing variation? A puzzle, in the purest sense, is "find the best move", and in this position, that move wins a pawn, and strategically improves an already strategically overwhelming position.

I think that even strong players play on in strategically lost positions, because the onus is still on the opponent to prove it and not stuff up... I suspect that is why Hmadi played on, not because he seriously thought he had a chance against best play... The other reason he played on might have been that he would have known Nunn was most likely to sac on g7, after which at least Nunn has made a material investment, so even though he would have known he was dead against best play even after Bxg7, he still puts the onus on White to get it right. So I don't think the fact that black played on means that this position after 21.Bxh6 is not winning for white.

The question of when to analyze and when to draw strategical conclusions or make positional judgements is to a meaningful degree stylistic, in that chess players with different styles and ways of thinking will differ as to how they decide on their moves. If you want to analyze what happens if he doesn't take the bishop, its easy to work out that he has to play 21...f5 which is the only way to meet the threat of 22.Rg3 by 23...Rf7 without losing the exchange or creating a 'sea of cheese' after 21...Re8 22.Rg3 g6, when ideas like Qd4 and rook sac on g6, or h4-h5, don't need to be analyzed... one way or another, black's position will crumble.

So anyway, if it is your style to analyze after 21...f5, then go for it... I still think that the position is correctly solved without doing so.

I also think that the choice between 21.Bxh6 and 21.Nb6 is stylistic to an extent...Do you like to win a pawn and swarm all over a poorly defended enemy king, or do you like to occupy strategical strong points, win a pawn, stick a pawn on the seventh, and watch your opponent get squeezed to death? Both moves fit with the strategical character of the position by exploiting weaknesses in the enemy camp, and they both win material and improve already exceedingly strong positions.

Here is my reason for preferring Bxh6 over Nb6.... I think whites play on the kingside could be diminished soon if not Bxh6 now, because there is just one static weakness on h6, which will be hard to exploit if black gets some defenders over there. Personally I'd cash in on the kingside now before he can do that, because at worst you can retreat the bishop, say thanks for the pawn, and continue to play on the queenside, where the static weaknesses on a6, b6, c6 and d6 are not going away in a hurry. I do think the kingside attack will win with best play, and the reason I am happy to trust that intuitive judgement is because I CAN bug out with a pawn and a queenside attack if in the ensuing moves I think black is defending OK.

This post is continued in the next (ran out of space)

Dec-14-07  UdayanOwen: Finally, I hear what MostlyAverageJoe is saying that if you don't have very strong positional judgement, the tendency is to want to verify things with further analysis. What I am suggesting though, if one wants to get stronger, is not say, well I'm a bit weak with my strategical reasoning and positional judgement, so I'll just analyze further even though the position is not forcing. Instead, an alternative is to take the opportunity to start stretching oneself into developing these skills of strategical reasoning and positional judgement.

Dvoretsky calls for this when he says combinational training should be a two-fold process, one where you calculate things exhaustively, and another where you think more thematically and find moves and trust your judgement without analyzing everything to the death. The latter is a critical skill, because at times, a strong sac will be available that cannot be analyzed to the end, but that 99 out of 100 GMs would play on positional grounds. Even more importantly, when analyzing you can rule out all kinds of sidelines and save clock time for more critical moments if you don't have to analyze every possibility down to the death.

To further defend my point of view here, I have a book "how to think in chess" which integrates a wealth of scientific studies examining the thought processes of strong players. In the introduction, the authors allude to the findings of De Groot, the pioneering and still towering figure in this area of research, who found that GMs typically do not analyze more or longer variations than the average player.

The authors the go on to give a couple of extremely dynamic sacraficial games with no analysis, followed by quotes by the winners. After beating Pilz in 1934, Najdorf said "this game was awarded the first brilliancy prize and nobody was more surprised than me since I can remember at no time seeing more than two moves ahead" Similarly, after smashing the great Tal in 1982, Nunn himself was quoted as saying "I hardly calculated a single variation more than a couple of moves deep during the entire course of the game".

Take it easy peoples... and bring on the debates :-)

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