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Sep0316
  patzer2: For today's Sunday puzzle I considered the positional 20...Qh3 and the tactical 20...Nxf2. I picked 20...Qh3 and rejected 20...Nxf2 simply because I didn't realize Black has a strong advantage after 20...Nxf2 21. Kxf2 Ne5! (0.75 @ 22 depth, Deep Fritz 15) as the second player threatens mateintwo after 22. Nxe5?? (diagram below) click for larger view22...Qxh2+ 23. Kf1 Bh3#.
While avoiding the 22. Nxe5?? Qxh2+ 23. Kf1 Bh3# blunder, White (as <dfcx> observes) still made a decisive mistake with 22. Qb1? allowing 22...Nxf3 23. Nxf3 Bxf3 (6.01 @ 21 depth, Deep Fritz 15). As <Abunnaser> notes, after 20...Nxf2 21. Kxf2 Ne5 the strongest White defense is 22. Bc3 (0.74 @ 22 depth, Deep Fritz 15) when Black maintains a small advantage with a lasting initiative. <mel gibson>'s suggestion 22. Kg1 is also good, but it appears to simply transpose to the 22. Bc3 line below after 22. Kg1 Nd3 Bc3 (0.74 @ 22 depth, Deep Fritz 15). Playing out the improvement 22. Bc3 movebymove to 20 depth on Deep Fritz 15, white has a strong advantage but no clear win in sight after 22. Bc3 Nd3+ 23. Kg1 Nxe1 24. Bxe1 Rxe3 25. Bd2 Ba7 26. h4 Bxf3 27. Bxf3 Rc4 28. Kg2 (28. Bxe3 Qxe3+ 29. Kg2 Bxd4 30. Qd1 Rc3 31. Rc2 Qg1+ 32. Kh3 Qxd1 33. Bxd1 b5 34. Rxc3 Bxc3 35. Kg2 Bd2 36. Bb3 d4 37. Kf3 Bc1 38. a4 bxa4 39. Bxa4 h5 40. b5 axb5 41. Bxb5 f5 42. Ke2 g6 43. Kf3 Kg7 44. Bd3 Kf6 45. Bc4 Bd2 46. Bd3 Ke5 47. Bc4 Ba5 48. Bd3 Bb4 (1.14 @ 36 depth) 28... Bxd4 29. Qd1 Kf8 30. Bxe3 Qxe3 31. Rd2 Bb6 32. Re2 Qc1 33. Qxc1 Rxc1 34. Rd2 Rc3 35. Rxd5 Ke7 36. a4 Rb3 37. b5 Bc7 (0.83 @ 24 depth). Like <YouRang> and <Steve.Patzer>, I was pleased to see the computers preferred my 20...Qh3 pick. Initially, I wasn't convinced the positional 20...Qh3 was better than the tactical 20...Nxf2 demolition. However, after playing 20...Qh3 out movebymove to 20 depth on a fairly fast desktop computer (3.6 GHz, Quad core i74790 with 16 GB RAM), I became convinced it wins after 20...Qh3 21. Be2 Nxd4 22. Bxd4 Rc6 23. Nh4 Bxe2 24. Rexe2 g5 25. Nf3 Qh5 26. Kg2 Rh6 27. Qh1 g4 28. Nh4 Bd6 29. Kf1 Be7 30. Ng2 Rc6 31. Ra1 Bd6 32. Nf4 Bxf4 33. exf4 Rce6 34. Rb2 Nd6 35. Rbb1 Nc4 36. Rd1 Nxa3 37. Rac1 (37. Rxa3 Qh3+ 38. Qg2 Re1+ 39. Rxe1 Rxe1+ 40. Kxe1 Qxg2 ) 37... Nc4 38. Qg2 Re2 39. Be5 Ra2 40. Kg1 Nxe5 41. fxe5 Rxe5 42. Ra1 Rb2 43. Rab1 Rxb1 44. Rxb1 Re7 (1.96 @ 23 depth, Deep Fritz 15). 

Sep0316   RandomVisitor: After 20.g3 others have pointed out that the machine prefers 20...Qh3. This is due in part to white having a potential improvement of 22.Kg1 in the actual line played. click for larger viewKomodo10.164bit:
<1.27/41 20...Qh3> 21.Be2 Ba7 22.Qd1 Qh6 23.Nh4 Nxf2 24.Kxf2 Qxe3+ 25.Kg2 Bxd4 26.Bxd4 Qe4+ 27.Kf2 Bxe2 28.Raxe2 Qxd4+ 29.Qxd4 Rxe2+ 30.Kxe2 Nxd4+ 31.Kd3 Ne6 32.Nf5 Kf8 33.Nd4 Nxd4 34.Kxd4 Rc2 35.Rh1 h5 36.Kxd5 b5 37.Kd6 g6 38.Kd5 Ra2 39.Kc5 Rxa3 40.Kb6 Ra4 41.Rb1 f5 42.Kc5 Ra2 43.h4 Ra3 44.Kb6 Kf7 45.Rc1 Rxg3 46.Kxa6 Rg4 47.Kxb5 Rxh4 48.Kc5 g5 

Sep0316   RandomVisitor: White's problems started with 18.Re1? when the guard was removed from the weak f2 square. Better might have been: click for larger viewKomodo10.164bit:
<0.14/30 18.Bd1> Ne7 19.Ne5 Bxd1 20.Qxd1 Bb8 21.Nef3 Rc4 22.Ra1 Rfc8 23.Qe2 Qh5 24.h3 Qg6 25.Rad1 Qd6 26.Qd3 Qc7 27.Qe2 f6 28.Qd3 Qd6 29.Rfe1 g6 30.Rf1 Kg7 31.Rfe1 Kh8 32.Rc1 Rxc1 33.Rxc1 Rxc1+ 34.Bxc1 Nc6 35.Qc2 Qd7 36.Bb2 

Sep0316   thegoldenband: I had the right idea but mixed up the move order, going for 20...Ne5 first and thinking that after 21. Nxe5 Nxf2 22. Bxg4 something would work out...but missing that the Ne5 attacks g4 as well. Oops. Black can bail out with 21...Bxd1 but then he's just worse. 

Sep0316
  patzer2: <RV> How does Komodo 10 assess 8. dxc5 as an improvement over 8. cxd5? One possibility is 8. dxc5 Bxc5 9. a3 OO 10. b4 Be7 11. Qc2 Bd7 12. Bd3 dxc4 13. Nxc4 = (0.24 @ 23 depth, Deep Fritz 15). 

Sep0316   NBZ: <drollere> I had the same line as you, but gave it up once I realized that Black does not actually win the exchange at the end. It's an interesting line  20 ... Nxd4 21. Bxd4 Bxf3 22. Bxf3 Nxf2 23. Kxf2 Qxh2+ 24. Kf1! and now the rook on a2 is attacking the queen, so Bxg3 is not possible. 

Sep0316   NBZ: <YouRang> As a puzzle maybe it is lackluster. But I think for an OTB player this is a great position to learn from. Suba's Nxf2 Kxf2 Ne5 is the kind of combination Tal used to specialize in: not always sound, there is rarely a clear line to victory, but horrendously difficult to face with the clock ticking. 

Sep0316   petemccabe: People who play the Retilike tactic of putting their queen on a1 must be so embarrassed when a game ends like this. 

Sep0316
  OhioChessFan: Saturday is usually when I get out of my depth, but this was a really straight forward sequence of forcing moves. I wish I'd noticed 20...Qh3 but the game continuation was pretty easy to spot. 

Sep0316   morfishine: <diagonalley> I enjoy your posts! 

Sep0316
  agb2002: Only a couple of pawns have been traded off per side. Black has a number of moves Qh3, Qh5, Nxd4, Ne5, Nxf2, Ng5, Re5, f5, etc. In the case of 20... Nxf2, taking advantage of the momentarily blocked rook on a2, 21.Kxf2 (else drop a pawn with a rather bad position) A) 21... Nxd4
A.1) 22.Nxd4 Qxh2+ 23.Kf1 Bh3#.
A.2) 22.Bxd4 Bxf3 23.Kxf3 and the attack seems to vanish. B) 21... Ne5
B.1) 22.Nxe5 Qxh2+ as in A.1.
B.2) 22.Kg1 Nd3 23.Re2 Rxe3 and Black seems to have enough compensation for the piece (24.Bc1 Rxc1  +). B.3) 22.Qb1 Nxf3 23.Nxf3 Bxf3 24.Kxf3 (24.Bxf3 Qxh2+ and Q(B)xg3 with three pawns for the piece and attack) 24... Qxh2 and Black also seems to have enough compensation. 
I couldn't find the time today to produce a decent analysis but I think I'd play 20... Nxf2. 

Sep0316
  whiteshark: <morfishine: <diagonalley> I enjoy your posts!> Me, too <diagonalley: a magnificent attack, requiring the perspicacity to spot 21....NK5!  needless to say <diagonalley> failed to do so :(> minor correction: it's <21...NK4!> though. 

Sep0316   YouRang: <NBZ><As a puzzle maybe it is lackluster. But I think for an OTB player this is a great position to learn from. Suba's Nxf2 Kxf2 Ne5 is the kind of combination Tal used to specialize in: not always sound, there is rarely a clear line to victory, but horrendously difficult to face with the clock ticking.> Good point. There may be multiple moves that the computers think are about the same, but OTB, some are mundane, while one is more surprising and complicated, enhancing the chances of inducing a mistake. I think this was "lackluster" in the sense that there is no clear forcing win with best play (which is usually the case with GOTD puzzles), but that's not to say that it no interesting tries. 

Sep0416   RandomVisitor: <patzer2: <RV> How does Komodo 10 assess 8. dxc5 as an improvement over 8. cxd5?> click for larger viewKomodo10.164bit:
+0.35/32 8.dxc5 Bxc5 9.Be2 00 10.00 Qe7 11.a3 a5 12.Qc2 Rd8 13.Rfd1 Bd6 14.Nb1 dxc4 15.Bxc4 Bd7 16.h3 Rac8 17.Nbd2 h6 18.Ne4 Nxe4 19.Qxe4 Be8 20.Rd3 Bc5 21.Bc3 Rd6 22.Rxd6 Qxd6 23.Qg4 Qf8 24.Bd3 f5 25.Qc4 Bf7 26.Ne5 

Sep0816
  patzer2: <RV> Thanks! Given a choice, it's instructive how capturing the right pawn in the opening can make the difference between a good and a bad game. I wonder if anyone has written a book or a chapter about good and bad pawn exchanges. In this case, 8. cxd5 = to gave White an isolated pawn to target, but not such a good game due to Black's superior piece activity. It appears 8. dxc5 would have been better. 

Nov0219
  ajk68: The win is far from clear (to me) after 21...Ne5
22. Kg1 and black will have a modest advantage. Enough to win the endgame? It could easily ended up being a situation where the material advantage cannot be converted. 

Nov0219
  ajk68: I've set the Chessgames lab computer on the analysis after 21. Kg1 See if it comes up with something conclusive after deeper analysis. 

Nov0219   Walter Glattke: 21.Bxg3+ 22.Kg1 Qxe3+ 23.Kh1 Bxe1 24.Nxe1 Qxe3+ 

Nov0219   RandomVisitor: After 21...Ne5 black gets the advantage because he can win the exchange (knight for rook on e1) and the pawn on e3. click for larger viewStockfish_19102601_x64_modern:
<57/91 1:49:07 1.31 22.Bc3 Nd3+ 23.Kg1 Nxe1 24.Bxe1 Ba7 25.Bf2 Rxe3> 26.Rc2 Rce8 27.Qb2 Qf6 28.Kg2 Rd3 29.Be2 Bxd4 30.Nxd4 Rxd4 31.Bxd4 Rxe2+ 32.Rxe2 Qf3+ 33.Kg1 Qxe2 34.Qxe2 Bxe2 35.Kf2 Bc4 36.Bb6 f6 37.Bc5 Kf7 38.Ke3 Ke6 39.Kd4 Be2 40.Ke3 Bd1 41.Kd2 Ba4 42.Kc3 Ke5 43.Kd3 Bb5+ 44.Ke3 Bc6 45.Bb6 Ba4 46.h3 Kf5 47.Kd4 Bb3 48.Bc5 Ke6 49.Bf8 g6 50.Bc5 g5 51.Bb6 Bc2 52.Bd8 Be4 53.a4 Bc2 54.a5 Be4 55.Ke3 Ke5 56.Bc7+ Kf5 57.Kd4 Bg2 58.Ke3 Kg6 59.h4 Be4 60.hxg5 

Nov0219   botvinnik64: Actually, I thought the imminent threat of Qxh2+ to be so deadly that 21...Ne5 appears obvious. Are there other strong moves for Black here? Probably, his position is very powerful. 

Nov0219   eblunt: <botvinnik64> Yes, the problem with white's position is having 2 major pieces hemmed in in the corner, not able to influence play, whilst blacks big guns are all very active. 

Nov0219   RandomVisitor: <botvinnik64>< Are there other strong moves for Black here? Probably, his position is very powerful.>
Black has many threats, but it seems that white can counter them all if he does not play 21...Ne5 click for larger viewStockfish_19100908_x64_modern:
37/67 08:02 1.27 21. ... Ne5 <see above> 36/64 08:02 +1.99 21. ... Qh3 22.Bc3 Ne5 23.Kg1 Nc4 24.Ng5 Qh5 25.Bxg4 Qxg4 26.Ngf3 Re4 27.Rae2 h5 28.Nd2 Nxd2 29.Bxd2 Be5 30.Qd1 h4 31.Rg2 Qxd1 36/66 08:02 +2.62 21. ... Re4 22.Nxc6 Rxc6 23.Bd4 Bxf3 24.Bxf3 Qxh2+ 25.Kf1 Qxg3 26.Rf2 Qh3+ 27.Bg2 Qd7 28.Bxe4 dxe4 29.Rc1 Rh6 30.Qb1 Rh1+ 31.Ke2 Rxc1 36/61 08:02 +2.72 21. ... Ba7 22.h4 Bh3 23.Bc2 f6 24.Bf5 Nxd4 25.Bxd4 Bxf5 26.Bxa7 Qh5 27.Nd4 Be4 28.Qd1 Qf7 29.Qg4 Rc4 30.Bc5 Qc7 31.Qf4 Re5 36/71 08:02 +3.34 21. ... Qh5 22.Kg1 Nxd4 23.Nxd4 Ba7 24.Bxg4 Qxg4 25.Qd1 Qxd1 26.Rxd1 Rxe3 27.Ba1 Rce8 28.Kg2 f6 29.Rdd2 R3e7 30.Nb3 Kf7 31.Nc5 a5 3 

Nov0219
  Breunor: AjK68, on 22 KG1, I'm getting a 1 after a 28 ply search with a win of the exchange: 1) 1.00 (28 ply) 22...Nd3 23.Bc3 Nxe1 24.Bxe1 Rxe3 25.Bd2 Ba7 26.Kh1 Rce8 27.Be2 R8e4 28.Qc1 Bxd4 29.Nxd4 Rxe2 30.Bxh6 Re1+ 31.Kg2 Rxc1 32.Bxc1 Rxd4 33.Rd2 Rxd2+ 34.Bxd2 f6 35.Bc3 Kf7 36.Kf2 Ke6 37.Ke3 Bf5 38.Bd4 Be4 39.Kf4 h5 40.h4 b5 

Nov0219
  agb2002: Black has a pawn for a knight.
The knight on f3 protects h2 and d3 is weak. These details suggest 21... Ne5: A) 22.Nxe5 Qxh2+ 23.Kf1 Bh3#.
B) 22.Qb1 Nxf3
B.1) 23.Nxf3 Bxf3
B.1.a) 24.Kxf3 Qxh2 and Black will get three pawns for the piece and keep the attack. B.1.b) 24.Bxf3 Qxh2+ 25.Kf1 (25.Bg2 Bxg3+ 26.Kf1 Bxe1 27.Qxe1 Rc2 seems to win) 25... Rc2 26.Re2 (26.Be2 Bxg3 and mate next) 26... Rxe2 27.Bxe2 Bxg3 wins. B.2) 23.Bxf3 Qxh2+ 24.Bg2 Bxg3+ 25.Kf1 Bh3 wins (26.Bxh3 Qf2#; 26.Qc2 Qh1+ 27.Ke2 Qxg2+ 28.Kd1 Qxc2+ 29.Kxc2 Bxe1). C) 22.Rh1 Nd3+
C.1) 23.Kg2 Bh3+ 24.Kg1 Qxe3#.
C.2) 23.Kf1 Bh3+ and mate next.
C.3) 23.Ke2 Qxe3+ 24.Kf1 Qf2#.
C.4) 23.Kg1 Qxe3+ 24.Kg2(f1) Qf2#.
D) 22.Nf5 Nd3+ and 23.Bxf5 looks winning.
E) 22.Kg1 Nxf3+
E.1) 23.Bxf3 Bxf3 24.Nxf3 Rxe3 25.Rf1 (25.Rxe3 Qxe3+ 26.Kg2 Rc2+ followed by Qxf3) 25... Re2 looks very good for Black. For example, 26.Bc1 Ba7+ 27.Kh1 Qh3 28.Rg1 Rxa2 29.Qxa2 Bxg1 30.Nxg1 Qe6 with rook and two pawns for bishop and knight. E.2) 23.Nxf3 Bxf3 24.Bxf3 Rxe3 looks similar to E.1. For example, 25.Rf1 Ba7+ 26.Kg1 Rxf3 27.Rxf3 Rc2 28.h4 Qd2. 

Aug1821
  Plaskett: I think Miles was knackered following a long grinding down by Beliavsky.
Incidentally, and apropos ...Bf5, when Mestel slaughtered me here  Plaskett vs A J Mestel, 1988
it was the specific victory of MilesSuba I had in mind! In our post mortem I said to a passing Chandler "You put it here, sometimes". He replied quietly, "You NEVER put it there". (He a specialist in IQP positions resulting from his youthful espousal of 2 c3 Vs the Sicilian.)
Always irked me that I did not mention to him the incentive provided by Suba´s slaughtering of Miles to Murray so, 33 years later, I´ll here do that. 


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