Annotated Game #146: Fog on the tactical horizon

This last-round tournament game is primarily interesting for the calculation error which leads to my loss.  I correctly spot the way to take advantage of White's move 19 oversight, but lose my way in the tactical complications.  First, I missed the very important in-between move that White has on move 20.  Second, I despaired once I saw that all of the options for Black were apparently bad.  I dismissed 20...cxd5 out of hand, once I saw that Black's knight could not escape following its pin against the queen with 21. Rc1.  However, this was a premature shortening of the calculation horizon, as Black has an impressive desperado tactic with the knight to end up with two rooks for a queen and a positional edge.  In the actual game, I picked the worst recapture option on d5, trying to complicate matters for White, who then showed impressive calm and skill to finish me off carefully, with a nice deflection tactic at the end.

[Event "?"] [Site "?"] [Date "????.??.??"] [Round "?"] [White "Class B"] [Black "ChessAdmin"] [Result "1-0"] [ECO "D16"] [Annotator "ChessAdmin/Houdini/Komodo 8"] [PlyCount "63"] [EventDate "2013.01.21"] [EventRounds "7"] {D16: Slav Defence: 5 a4: Lines with 5...Bg4 and 5...Na6} 1. d4 d5 2. c4 c6 3. Nf3 Nf6 4. Nc3 dxc4 5. a4 Na6 {although this is the main line Slav, this is the first time I have had a chance to play it in recent memory. This is called the Lasker variation, after the world champion who employed it.} 6. e4 Bg4 7. Bxc4 e6 8. Be2 {breaking the pin, although a small waste of time.} (8. Be3 Be7 9. a5 O-O 10. Qb3 Bxf3 11. gxf3 Qc7 12. O-O Rad8 13. Rfd1 Ne8 14. f4 Nd6 15. Bf1 Kh8 16. f3 Qc8 17. Rac1 Nc7 18. Kh1 Qb8 19. Na4 Ndb5 20. Nc5 a6 21. Rd2 Ne8 22. Bh3 g6 {Schmidt,W (2430)-Smyslov,V (2550) Moscow 1980 1/2-1/2 (43)}) 8... Be7 $146 9. O-O O-O 10. Bg5 Nb4 $11 {the point of the Na6 development. The knight is well-placed on b4 and helps counterbalance White's space advantage in the center.} 11. Re1 a5 {with the idea of consolidating the b4 outpost.} 12. h3 Bxf3 {I felt the trade was worth it, given that the knight could go to e5 and be strongly positioned otherwise.} 13. Bxf3 Re8 {this is OK, but the engine points out that challenging in the center would be better.} (13... Nd7 14. Be3 e5 15. d5 Bc5 $11) 14. Qd2 $6 {this would allow Black to get in the ... e5 break for free, although I did not understand the idea myself at the time.} (14. Be3 Qc7 $11) 14... Qb6 (14... e5 {and now White's nice pawn center is disrupted. For example} 15. dxe5 Qxd2 16. Bxd2 Nd7 {and the advanced e-pawn will fall.}) 15. Rad1 Rad8 16. Be3 Qc7 {a repetition of moves would occur if White now played Bf4. Black's position is solid, but there is no obvious winning strategy to pursue.} 17. Qe2 {White correctly chooses to reposition his queen.} h6 {a prophylatic move that prevents intrusion on g5.} 18. e5 { although White gets more space, this simply drives the knight to a better square.} Nfd5 19. Bd2 $6 {blocking the defender of the d-pawn.} (19. Bc1 Rd7 $11) 19... Nc2 {This was the best move, but I calculated the follow-up incorrectly. I only saw after the the move the intermediate capture on d5 and then thought that after cxd5, White has Rc1 pinning and winning the knight.} 20. Nxd5 Rxd5 $2 {a hallucination from my incorrect calculation of the consequences of cxd5; I stopped calculating the variation too soon, once I spotted the knight would be pinned against the queen and could not be saved.} ( 20... exd5 {did not look good either, due to Bxa5 winning a pawn with the discovered attack on the Nc2. I thought the rook capture made in the game would at least complicate things for White, but I missed the bishop retreat on move 22 cutting off the knight.}) (20... cxd5 {in fact works, however, although I was unable to visualize it and simply assumed that there was no way to rescue the knight.} 21. Rc1 (21. Bxa5 Qxa5 22. Qxc2 Rc8 {and White picks up the a-pawn.}) 21... Rc8 22. Qd1 Nxe1 $1 {this desperado tactic gives Black at least equality, according to the engine.} 23. Rxc7 Nxf3+ 24. Qxf3 Rxc7 { and Black has two rooks for the queen, in a position well suited for them (domination of the c-file, limited attacking prospects for the queen).}) 21. Bxd5 $18 Nxe1 (21... exd5 22. Bxa5 $1 {Decoy: a5} Qxa5 23. Qxc2 $18) 22. Be4 { after this, which dominates the knight's escape squares, I try to play actively in hopes of a swindle, although I recognized the game was lost. My opponent played coolly and carefully to bring home the point.} f5 23. exf6 Bxf6 24. Qxe1 Rf8 25. Bxa5 Qf4 26. Bb4 Rd8 {by this point I could have resigned.} 27. Qe3 Qh4 28. Bc5 Bg5 29. Qf3 b6 30. Bxb6 Rf8 31. Bh7+ $1 {nicely seen by my opponent.} Kxh7 32. Qxf8 1-0