Commentary: 2015 U.S. Championship, Round 4 (Wang-Foisor)

By coincidence, this game from the fourth round of the 2015 U.S. Championship (women's section), like the previous commentary game from round 2, features an Exchange Slav.  Also like the previous game, it is anything but boring.  Black follows a symmetry-breaking sideline starting on move 6 and introduces some positional imbalances with the pawn structure and central control.  White fails to challenge Black effectively, missing an interesting tactical idea involving a temporary sacrifice followed by a pawn fork, then Black's space advantage eventually makes itself felt.  It is instructive to see Sabrina Foisor as Black effectively use her advantage to increase her positional edge before winning material, as well as calmly sort her pieces in the final phase before making a decisive penetration of her opponent's territory.

[Event "ch-USA w 2015"] [Site "Saint Louis USA"] [Date "2015.04.04"] [Round "4"] [White "Wang, Annie"] [Black "Foisor, S."] [Result "0-1"] [ECO "D13"] [WhiteElo "1901"] [BlackElo "2276"] [Annotator "ChessAdmin/Komodo 8"] [PlyCount "116"] [EventDate "2015.03.31"] [SourceDate "2015.02.07"] 1. d4 d5 2. c4 c6 3. cxd5 cxd5 4. Nf3 {White opts for a traditional Slav Exchange variation, unlike in Timur Gareev's round 2 game with Bf4.} Nf6 5. Nc3 Nc6 6. Bf4 Nh5 {a useful offbeat option, that scores the best of any 6th moves for Black in the database.} (6... Bf5 {is the classical response.}) 7. Be5 f6 8. Bg3 Nxg3 (8... Bg4 $5 {is the engine's preference, although there are no games in the database with this move. It looks somewhat counterintuitive, but perhaps is worth further investigation.}) 9. hxg3 e5 {the natural follow-up to the ...f6 push. Black gains some central space.} 10. e3 (10. dxe5 $6 {doesn't work due to} d4 {and now} 11. Nb1 Qa5+ 12. Nbd2 fxe5 $15) 10... e4 11. Nd2 Be6 {developing the bishop and overprotecting d5.} 12. a3 {not the most challenging approach.} (12. Ndxe4 {is now tactically possible, due to the pawn fork on d5.} dxe4 13. d5 Bxd5 14. Qxd5 (14. Nxd5 Qa5+ $11) 14... Qxd5 15. Nxd5 O-O-O 16. Rd1 {here Black's king position is a little airy and White's pieces have slightly better prospects, although after Black tucks his king away with . ..Kb8 the position looks safe enough.}) 12... Be7 $6 {Black here seems to either overlook or discount the possibility of the pawn fork trick Ndxe4, which now after a3 has been played could lead to more of an advantage for White.} (12... f5 $5 {would address the issue.}) 13. Be2 (13. Ndxe4 dxe4 14. d5 Bxd5 {and now} 15. Nxd5 {is much more awkward for Black than in the above variation.} Qa5+ {is no longer good, due to the pawn advance b4, protected an additional time by the a3 pawn.}) 13... O-O 14. b4 {in these types of positions Black appreciates the fact that the b-pawn advance leaves a wake of weakened squares. The more advanced b-pawn can also be undermined.} f5 ({ If Black preferred to play on the queenside, one approach might be} 14... a5 15. b5 Nb8 16. Qb3 Qd6 17. Na4 b6 18. O-O Nd7 $11) 15. Nb3 {White repositions her worst piece, always a good strategic principle.} Bf7 {anticipating a White Nc5.} 16. Rc1 (16. Nc5 {is still a logical follow-up, as the knight cannot easily be forced to retreat. For example} b6 (16... Rb8 $5) 17. Na6 {and even though it is on the rim, the Na6 is rather annoying for Black.}) 16... a5 { this pawn break is now more obvious, especially with the Nb3 as a potential target of the advancing pawn.} 17. b5 Na7 18. a4 {this shuts down further advances by the a-pawn, but gives up the diagonal to Black's bishop.} b6 { Black decides to close off c5 before doing anything else.} (18... Bb4 $5) ( 18... Rc8 $5) 19. Bh5 {White overoptimistically tries to distract Black with play on the kingside. The bishop of course cannot be exchanged without giving White an attack.} g6 $15 {however, with this simple move, which has no real drawbacks for Black, White effectively loses a tempo and Black gains the initiative. The engine has shown a small plus for Black for several moves; at this point it becomes more evident.} 20. Be2 Qd6 {the queen occupies the best logical square for the knight currently stuck on the rim (Na7-c8-d6). However, we will see there are compensations for this.} 21. O-O h5 22. Qe1 Rae8 { this gets the rook into the game, so at least there aren't two unproductive pieces on the a-file. However, it could be of more use on the c-file, and eventually goes there.} 23. Nb1 {Black's space advantage is now obviously seriously cramping White.} Bd8 24. Rc2 Kg7 {getting the king out of the way of the rook, so it can go to the h-file. This could also have been played a move earlier.} 25. Qc1 Rh8 {White now faces a serious problem on the h-file and the kingside in general, with Black threatening to advance ...h4 and crack open his position.} 26. f4 $6 {White probably did not want to be squeezed to death and tries to get some space here. Unfortunately the resulting opening of the position is better exploited by Black.} exf3 27. Rxf3 Qb4 $17 28. N3d2 Bg5 { the bishop finally gets active.} 29. Nf1 {White's structure at this point is simply awful, with doubled g-pawns and a backward e-pawn that desperately needs protection. All White has going for her at this point is the c-file, which however can be easily challenged by Black.} Rc8 (29... Qxa4 {is also possible, but pawn snatching is not necessary for Black to further improve her position.}) 30. Rxc8 (30. Nc3 $5 {would put up stronger resistance.}) 30... Rxc8 31. Qd1 {now Black controls the c-file as well, with additional threats after her next move.} Qb2 $19 32. Qd3 Rc1 (32... Rc2 {would have been my natural preference, establishing the threat on the second rank, and is still winning; the text move is more effective, however.}) 33. Nbd2 Rc3 34. Qb1 Qa3 35. Qe1 Rc1 36. Qf2 Qxa4 {collecting the pawn is perhaps the simplest way forward and an easy decision before the time control.} 37. Bd3 Be6 {wisely stifling any counterplay involving a sacrifice on f5.} 38. Qe2 (38. Bxf5 Bxf5 39. Rxf5 gxf5 40. Qxf5 Be7 41. Qe5+ Bf6 42. Qxd5 Nc8 $19) 38... Qb4 (38... Qd1 {would head for a simplified and won endgame, but Black prefers to keep up the pressure in the middlegame.}) 39. Kh2 a4 {passed pawns must be pushed!} 40. Rf2 a3 41. Nf3 Bf6 42. Nh4 Bxh4 {well worth exchanging at this point, as the bishop was not doing much otherwise and it eliminates a possible attacker.} 43. gxh4 Bd7 {going for the obvious b5 target.} 44. Qf3 Qd6+ 45. Ng3 Nxb5 {at this point it's hard to see how Black could possibly lose, although White perhaps was pinning some hope on a sacrificial kingside breakthrough.} 46. Qe2 Nc7 ( 46... Qe7 {would be an elegant tactical way of meeting the threat, with the idea being ...Qxh4 followed by Qxg3.}) 47. Qd2 Rc6 {Black over the next few moves sorts out her pieces and then finally gets her queenside pawns moving, which decides the game.} 48. Rf4 Ne6 (48... b5 {immediately is more effective, as White cannot stop the next move to b4 and Black puts more pressure on her opponent immediately. It is instructive to note, however, that Black having built up such a positional advantage can take the time to sort her pieces - especially the knight - while keeping her winning advantage in hand.}) 49. Rf3 Rc8 50. Kg1 Nf8 51. Qf2 Rc1+ 52. Kh2 Nh7 53. Qd2 Rc7 54. Kg1 Nf6 55. Ne2 b5 56. Bb1 b4 57. Qd3 Ne4 {the knight, after many moves, reaches a dominant square and then deals the final blow. Black surely planned to play ...Nc3 next, but White now offers a better target.} 58. Qb3 Nd2 0-1