22 September 2015

The trouble with eliminating candidate moves

I've posted before on the importance of CCT (checks, captures and threats) in generating candidate moves, especially the importance of not eliminating any of them prematurely.  It's often easy to mentally eliminate or ignore possibilities simply because they don't work at the 2-ply (one move) level of thinking.  Of course it doesn't make sense in your thinking process to endlessly recalculate capturing protected pieces that would simply result in losing material.  But it is worth looking at tactics that might eventually work if the board situation changes, either through what you do or your opponent does.

IM Silman over at Chess.com just published the article "Deadly Mindsets: He Can't/I Can't" that offers a look at this phenomenon, including a very timely example from this year's World Cup (Adams - Laznicka).  In the case of this game, it really is a one-move threat, but it visually doesn't look at first as if it should work.  These types of moves are much harder to visualize as well, since the tactic involved (a pin) may not register as easily on the mental chessboard, which is what I'm sure Black was relying on at the beginning of the sequence.

In other news, I'll be on vacation for a couple of weeks from both work and chess.  Should be good to clear the mind and then return ready to work / play harder once more.

13 September 2015

Commentary: 2015 U.S. Championship, Round 10 (Nemcova - Paikidze)

I'll finish off my commentary on selected games from the 2015 U.S. Championship with the round 10 game featuring Katerina Nemcova (whose round 9 game was previously featured) and Nazi Paikidze (whose games in round 7 and round 8 were also examined). White in this game avoids the line in the Classical Caro-Kann (11...a5!?) that Paikidze used in round 8, instead deviating early with the interesting sideline 6. Nh3.  This has some aggressive potential, as shown by the 9. f4 advance, but White is a bit slow to develop and Black equalizes by the early middlegame. After that it is a strategic war with tactical undertones, as the position's pawn structure and minor pieces are significantly imbalanced.  Eventually White overreaches and Black calculates well to find a defense while waiting to execute her game-ending mate threat.

For Caro-Kann players of either color, this game holds a lot of interest, since a number of typical themes appear.  The results of the f-pawn advance for White and the decision to execute a pawn break on c5 for Black are perhaps the most important strategically, although other common structures and ideas are contained in the game.  The tactical threats (some executed, others not) are also important to pay attention to, especially what White could have done with a bishop on h2.

Original ChessBase news article and game commentary by GM Josh Friedel can be found here.

[Event "U.S. Womens Championship 2015"] [Site "Saint Louis"] [Date "2015.04.11"] [Round "10"] [White "Nemcova, Katerina"] [Black "Paikidze, Nazi"] [Result "0-1"] [ECO "B18"] [WhiteElo "2279"] [BlackElo "2333"] [Annotator "ChessAdmin/Komodo 8"] [PlyCount "80"] [EventDate "2015.??.??"] [EventCountry "USA"] [SourceDate "2015.02.07"] 1. e4 c6 2. d4 d5 3. Nd2 {this move has little independent value, as Black almost always takes on e4 in response. However, an alternative is ...g6 followed by ...Bg7, in which case White will follow with c3, blunting the pressure on the long diagonal.} dxe4 4. Nxe4 Bf5 {the Classical Caro-Kann.} 5. Ng3 Bg6 6. Nh3 {an unusual choice. The knight normally goes to f3 and the development N1e2 used to be another popular significant option. The text move is obviously offbeat, but it scores well (58 percent) and has been used in some recent high-level games.} Nf6 7. Bc4 (7. Nf4 {would transpose to the N1e2 lines.}) 7... e6 8. O-O Be7 (8... Bd6 {is often used in the N1e2-f4 lines to fight for the f4 square and is the normal choice here as well. The text move indicates that Black in this game may have had a greater concern for the h4-d8 diagonal and the g5 square. Here's a recent game that parallels White's plan in the main game, using the f4 advance:} 9. f4 Qc7 10. Kh1 O-O 11. f5 exf5 12. Nxf5 Nbd7 13. Nxd6 Qxd6 14. Bf4 Qb4 15. Bb3 a5 16. c3 Qb6 17. Bd6 Rfe8 18. Nf4 Be4 19. Nh5 Bg6 20. Nf4 Be4 21. Nh5 Bg6 22. Nf4 Be4 {1/2-1/2 (22) Rozentalis,E (2604)-Prohaszka,P (2599) Austria 2015}) 9. f4 {now out of the database, although more because of Black's unusual bishop move. The text move is also usually played in response to ... Bd6 (as shown in the game quoted above). The f-pawn advance is a logical follow-up to Nh3 as an independent line, as White takes advantage of the f4 square being open (i.e. not occupied by a knight). It also influences g5 and e5 to White's advantage.} (9. Nf4 {is usually where the knight goes.}) 9... Qd7 {this doesn't appear to be a bad move and reinforces f5. However, it blocks the Nb8's development temporarily and the f-pawn's advance is not to be feared.} (9... O-O 10. f5 exf5 11. Nxf5 Bxf5 12. Rxf5 c5 $11) 10. Kh1 {this gets the king off the now-weak g1-a7 diagonal and removes future potential tactics involving exchanges on d4 or c5. However, it's also a bit slow and should allow Black to fully equalize.} (10. Be3 { played immediately should save a tempo and cover the diagonal.}) 10... O-O ( 10... c5 $5 {whenever Black can get this pawn break in effectively without king safety issues, it's normally a good idea. White doesn't appear to have anything useful to do in response. For example, the engine can only come up with} 11. f5 exf5 12. dxc5 Qxd1 13. Rxd1 O-O $11) 11. Be3 {this reinforces d4 and helps restrain ...c5. However, now that the king is off the diagonal, it's not the most effective use of White's time.} (11. Ng5 {would seem more to the point here, again logically following up on the presence of the Nh3. Otherwise the knight is effectively doing nothing. Chasing it away with} h6 $6 {would simply waste a tempo helping the knight to a better square, from where it could then go to e5 (a much better square).}) 11... c5 {White is now better positioned to combat this pawn break.} (11... Na6 {gets the knight into the game and White has nothing better than to exchange it. This shatters the queenside pawn structure, but in Black's favor are the two bishops and a semi-open b-file.} 12. Bxa6 bxa6 $15 {Komodo 8 gives Black a small plus here. Black's pieces are, in addition to the above points, better coordinated.}) 12. f5 {White chooses to try for some action on the kingside rather than trade in the center, which would lead to a more simplified position:} (12. dxc5 Qxd1 13. Raxd1 Bxc2 14. Rc1 $11 {although the engine rates this position as equal, White seems to have the easier position to play, at least for the short term.}) 12... Bxf5 (12... exf5 13. dxc5 Qc8 {would preserve the Bg6, unlike the text move. Although the bishop is more of a "big pawn", it does well as a defensive piece on the kingside and is certainly no worse than the Nh3.} 14. b4 (14. Nf4 Bxc5 $15) 14... Rd8 15. Qe2 Nc6 $11) 13. Nxf5 exf5 14. dxc5 Ng4 {Black at this point has achieved equality and just needs to complete her development. The text move is a nice way for Black to threaten the bishop and occupy a rare advanced outpost on the kingside.} 15. Bg1 g6 {Black should not be afraid to enter into this type of pawn structure when necessary, in this case to protect the advanced f-pawn. The dark square weakness can be covered by the bishop, while White's bishop is in no position to exploit it.} 16. Bd5 $6 {this looks overly aggressive. White needs to be careful about the weak c-pawn, which is easily attacked again, and also needs to bring the Nh3 into the game.} (16. b4 a5 17. c3 $11) 16... Qc7 17. b4 {the difference with the earlier variation is that the Qc7 is now pressuring c5 already. Also note the threat to h2 from the knight and queen, which means the Bg1 cannot currently move without allowing a mate.} Nc6 {Black finally has all her minor pieces developed, and to effective squares. The queen's rook will also go to a nice square on d8.} (17... a5 $5 { would more directly attack the exposed queenside.} 18. c3 axb4 19. cxb4 Bf6 20. Rb1 Nc6 {and Black now has the initiative, for example} 21. Qb3 Bd4 $15) 18. Rb1 Rad8 19. c4 b6 {Black has a number of reasonable choices here.} (19... Bf6 {preparing ...Be5 would redeploy the bishop effectively.}) 20. Nf4 {White wastes no more time in getting her knight back into the game.} bxc5 21. bxc5 { The doubled c-pawns may be a long-term weakness, but they're also passed pawns. White's pieces are also now working together much better.} Rb8 $6 {Black may have done this just on general principles, without looking at the tactics fully. If she could recapture on b8 with the rook, that would certainly help her position. Unfortunately it doesn't work out that way.} (21... Bg5 $5) ( 21... Rc8 $5 {would free the d8 square for the other rook and also line up on the weak pawns.}) 22. Rxb8 Nxb8 {ugly, but better than the alternative.} (22... Rxb8 {the main problem with this is that now when the White bishop goes to h2, it has targets on both c7 and b8.} 23. h3 Nge5 (23... Nf6 24. Bh2 Qd7 25. Bxc6 Qxc6 26. Nxg6 hxg6 27. Bxb8 $16) 24. Bh2 Bf6 25. Nd3 Re8 26. Qa4 $16) 23. h3 $14 Ne5 24. Re1 {White brings her rook to a more effective file and generates additional potential tactical problems for Black, now that the e-file is under pressure. The Qc7 is a bit overloaded, as it cannot protect the Ne5 and support an exchange on c5 at the same time.} Bh4 {Black's best option, getting the bishop off the e-file and gaining a tempo with the attack on the Re1.} 25. Re2 Nbc6 26. Bxc6 {this dissipates some of White's pressure. The knight will now also get off the e-file.} (26. Bh2 $16 {still looks very effective.}) 26... Nxc6 27. Qd6 Qc8 {Black naturally does not exchange on d6, which would create two monster passed pawns for White.} 28. Nd5 {this position is probably what White was looking at when she decided to exchange on c6. She still has an edge, but with fewer pieces on the board there are less attacking chances.} Re8 29. Rxe8+ Qxe8 {with the additional exchange, Black probably was looking to head into an endgame with a small disadvantage, but with good drawing chances. The c-pawns look like they can be blockaded effectively.} 30. Nc7 $6 {the idea behind this move is not clear to me. In the game, it results in Black's queen moving to a much more effective centralized position, without generating any evident threats.} (30. Bf2 {would be a clever tactical way to improve White's position and get the Black bishop off the h4-e1 diagonal. The bishop has to protect f6 due to the fork threat from the Nd5.}) 30... Qe4 $11 31. Qd5 Bg3 { the bishop is now free to move and attacks the Nc7 "backwards" along the diagonal.} 32. Nb5 Qe1 {with the threat of ...Bf2} 33. Nd6 $2 {White chooses to counterattack with a threat to f7, but she runs out of threats first, losing the game.} (33. Nd4 {is the necessary defensive move.} Nxd4 34. Qxd4 $11 ) 33... Ne5 $1 {holds everything together for Black.} 34. Qa8+ {this starts a long sequence where Black's king is chased almost the entire length of the board, but eventually finds refuge.} (34. Nxf5 gxf5 35. Qd8+ Kg7 36. Qg5+ Ng6 $19 {is the best try for White, but still leaves Black winning. For example} 37. Qxf5 Be5 38. Qf2 Qc1 39. c6 Qxc4 {and Black's material advantage is decisive.}) 34... Kg7 35. Ne8+ Kh6 36. Nf6 Bf2 {Black had to calculate everything precisely to proceed with this move, but saw correctly that White would not be able to deliver mate or get a perpetual check.} 37. Qf8+ Kg5 38. Nxh7+ Kf4 39. Qh6+ Ke4 40. Ng5+ Kd3 {White has run out of moves and mate on g1 is coming.} 0-1

05 September 2015

Commentary: 2015 U.S. Championship, Round 9 (Ni - Nemcova)

The following commentary game continues the series from this year's 2015 U.S. Championship.  The round 9 game between Viktorja Ni and Katarina Nemcova features a struggle in the English with a number of typical strategic choices and positional characteristics, even if it went out of the database relatively quickly.
  • White opens up the queenside and gains space, following the standard plan of pushing the b-pawn, but this is a two-edged sword; in this game, Black could have more effectively exploited the queenside opening (on the a- and b-files) for her own purposes.  
  • White made an unusual decision to develop early and exchange her dark-square bishop.  She eliminated an often dangerous kingside piece for Black (the Nf6) but this of course came with drawbacks (such as giving Black the two bishops).  
  • The choice of where to put White's queen (on d2 or c2) is also a typical problem that I've run across.  From my own experience, it seems that it's easy to make the wrong choice, even if (or especially because) it is not an obvious error.
  • Black's decision to delay initiating her kingside counterplay (with ...f5) may have cost her time and the opportunity to more effectively pressure White.
  • The choice by Black to exchange White's fianchettoed bishop is also worth studying for both sides.  The White player in the English, for example, should have a good idea of when it is advantageous to initiate the exchange on h3 in such situations.
For those interested, the original commentary on the game by GM Josh Friedel can be found on the ChessBase site (as well as the news item for what most people paid attention to in Round 9, the infamous arbiter decision to forfeit GM Wesley So).
[Event "U.S. Womens Championship 2015"] [Site "Saint Louis"] [Date "2015.04.10"] [Round "9"] [White "Ni, Viktorija"] [Black "Nemcova, Katerina"] [Result "1/2-1/2"] [ECO "A26"] [WhiteElo "2188"] [BlackElo "2279"] [Annotator "ChessAdmin/Komodo 8"] [PlyCount "90"] [EventDate "2015.??.??"] [EventCountry "USA"] [SourceDate "2015.02.07"] 1. c4 e5 2. Nc3 Nf6 3. Nf3 Nc6 4. a3 {White has many playable options on move four of the English Four Knights variation. This one is more in the spirit of a reversed Sicilian, but can also transpose to more standard English positions (as happens in the game).} g6 {this is a standard English way to develop the bishop and scores relatively well for Black (around 47 percent).} (4... d5 { would be the way to directly challenge White, in the style of the Open Sicilian (reversed). However Black only scores 42 percent in this line.}) 5. d3 Bg7 6. Bg5 {this isn't found in many high-level games and is an accelerated development of the dark-square bishop.} h6 7. Bxf6 {consistent, otherwise White loses time retreating the bishop. The game is now already out of the database.} Bxf6 8. g3 O-O 9. Bg2 Bg7 {the bishop retreats to protect h6 and get out of the way of the f-pawn.} 10. O-O {White now has a rather standard-looking English position, as does Black.} d6 11. Rb1 {White's typical plan is to use the b-pawn advance to expand on the queenside and push the Nc6 away, leaving the long diagonal open for White's bishop.} a5 {Black chooses to (temporarily) challenge the b-pawn advance, rather than move forward with other development and preparing counterplay on the other wing. The text move will result in opening the a-file for Black's rook, after the pawn exchange.} 12. b4 axb4 13. axb4 Be6 14. Nd5 $6 {while it's a key principle of the English to occupy d5 with a knight when advantageous, it's often difficult to understand when it is best to do so. Here the knight move is premature, as it would allow Black to block the long diagonal more effectively.} (14. b5 Ne7 15. Qc2 {is a standard and good approach.}) 14... Qd7 {with the evident idea of playing ... Bh3 as a follow-up. This is rather slow, however.} (14... Ne7 $5 { and now} 15. Nxe7+ Qxe7 16. Nd2 c6 17. b5 d5 $15 {is good for Black. For example} 18. bxc6 bxc6 {and it's clear White has no threats, while Black has a strong center and better prospects on the queenside as well.}) 15. Nd2 { this now allows the bishop to support the Nd5, which is in a strong position.} (15. b5 Ne7 16. Nd2 {would also be fine. If the Nd5 is exchanged, White would have doubled d-pawns, but the strength of the d5 pawn would be compensation for that.} Bxd5 17. cxd5 $11) 15... Ra2 {not a bad move, but the resulting continuation is a little awkward for Black.} (15... Ra3 {is the rook move preferred by Komodo 8. The difference with the text move is that the rook on a3 controls c3 and cannot be challenged by a White knight.}) (15... Nd4 { is another possibility. The knight otherwise is going to be placed rather awkwardly after White's b-pawn advance. One sample continution:} 16. e3 Bxd5 17. cxd5 Nb5 $11) 16. b5 Nd8 {essentially forced, in order to protect the b7 pawn.} 17. Nb3 {the idea behind this move is apparently to support an eventual c5 advance. This eventually comes to fruition, but the knight is nevertheless not optimally placed.} (17. Nc3 {is the obvious move here, hitting the Ra2 and clearing the long diagonal for the bishop.}) 17... c6 18. Nb4 (18. Nc3 { is also still possible.}) 18... Ra8 19. bxc6 bxc6 20. Qd2 {it's sometimes difficult in the English to figure out the best square for developing the queen. In any case, it's important to get the rooks connected and maximize the queen's utility. Here the choice is between d2 and c2. On d2, the queen has open diagonals (c1-h6 and a5-e1) but it's not clear if they can ever be utilized. On c2, it might better support the queenside and would leave d2 open for the Nb3.} Bh3 $6 {Black follows up with her original idea of exchanging the Bg2.} (20... f5 {is perhaps more to the point, getting Black's counterplay on the kingside going sooner.}) 21. Rfd1 $6 {this effectively loses a tempo for White.} (21. Bxh3 $5 {an English player needs to know when to exchange the Bg2 like this. While Black's queen always looks threatening on h3, without the support of a knight or advanced pawns it will be less effective.} Qxh3 22. c5 { taking advantage of the Nb3's presence} d5 23. Ra1 $11) (21. Ra1 {is another alternative, challenging the Ra8.}) 21... Bxg2 $15 22. Kxg2 f5 (22... Ne6 $5 { would get the knight back in the game, connect the rooks and again control c5.} ) 23. c5 {evidently this was the idea behind the positioning of the Nb3.} d5 24. d4 e4 {Black by this point has a stronger center and more space, so White needs to turn her attention to trying to contain Black's threats.} 25. f4 { this can be a key defensive move for White in these position types.} exf3+ 26. exf3 f4 27. g4 (27. gxf4 $2 Ne6 28. Nd3 Qf7 $17 {and White's shattered kingside pawns will not provide an adequate defense.}) 27... Ne6 28. Re1 Ra3 $6 {making this rook more active isn't a bad idea, but again this is not the best square for it on the a-file.} (28... Ra4 {exerts indirect pressure on d4 and can't be chased off by a knight.}) (28... Rfb8 $5 {gets the other rook into the game effectively and illustrates how White's opening of the queenside can also be a weakness, with Black's rooks looking much better placed.}) 29. Nc2 Raa8 $6 {this makes the maneuver just a waste of time.} (29... Ra4) 30. Qd3 ( 30. Na5 $5 {threatening Rb7 is an interesting idea.}) 30... Qf7 31. Re2 $11 { at this point White has blunted Black's initiative and can start manuevering again.} h5 {a good practical move by Black, as White does not find the best continuation.} 32. h3 $6 {this sort of defensive move is often instinctual, as it appears more solid than exchanging on h5. However, in that event White will be the one controlling the g-file, so it's actually better.} (32. gxh5 gxh5 33. Rg1 $11 {followed by Kh1 and White is fine.}) 32... hxg4 (32... Qf6 $15 { threatening to penetrate on the kingside, looks more effective.}) 33. hxg4 Rae8 {this removes Black's possibility of making threats on the a-file. If Black wants a rook on e8, Rf8-e8 makes more sense, since the f-pawn is already overprotected.} 34. Rbe1 {White again looks fine, now that Black's threats have dissipated.} Bf6 $6 {this is too slow and allows White some initiative.} ( 34... Qf6 $5) 35. Nb4 {now the knight is not tied to the d-pawn and can make threats of its own.} Nd8 {the only way to protect the c-pawn without losing something somewhere else.} 36. Rxe8 $6 {this is not forced and is a good example of how it is often better to maintain tension and even increase it, rather than release it prematurely.} (36. Na5 {would be the most challenging for Black, who would then have to find} Bh4 {to keep things equal.}) 36... Rxe8 37. Rxe8+ Qxe8 38. Qd2 {at this point the position looks equal/drawn, so perhaps White simply wanted to head for a draw earlier.} Ne6 39. Na5 Nxd4 { one of multiple drawing continuations. White will win the d5 pawn with her queen, but this leaves the back ranks open for Black's queen to penetrate and give perpetual check.} 40. Naxc6 Nxc6 41. Qxd5+ Kg7 42. Nxc6 Qe2+ 43. Kg1 Qe1+ 44. Kg2 Qe2+ 45. Kg1 Qe1+ 1/2-1/2

03 September 2015

Why World Champion Max Euwe Played the Slav Defense

I've posted previously here Why I Play the Slav, but it's also worth reading GM Bryan Smith's article on Chess.com on why World Champion Max Euwe played it in his matches against Alexander Alekhine.  It's not a completely one-sided tale, as Euwe did not fully rely on it as Black and also played against it (with success) as White.  This fact helps reinforce the idea that true opening mastery is about deep understanding of positions, not an emotional commitment to your chosen side.  It's also worth noting that Slav players (like myself) doing their own research into the opening with today's databases will undoubtedly run across games from Euwe in still-critical lines.  It's nice to see lessons from the 20th century still applicable to today's games.