Checkmate race in the Slav defense

After a long break I played again in the Hungarian team championship league on Sunday at 2nd of February. I was excited before the game. I planned to use my prepared ideas in the slav defense. 2 years ago I helped an Indian student, a woman grandmaster, to play well against the slav defense. Our main ideas were to get the pair of bishops and space advantage in the opening and improve the pressure in the middlegame to break the black position.

My opponent played a6 instead of the main move 5...e6 and I forgot the strongest move Qb3 and got a close to equal position in the opening. I castled early. He stayed in the middle and started an attack against my king in the kingside. Then I decided to sacrifice a pawn on the queenside to open the position. In the mating race he played a good looking f4-f3 move to open the way for his queen, but it was too slow and from the equal position I got a winning attack.

Let us look the game:

You can study the game also with diagramms:

1. d4 d5 2. c4 c6 3. e3 Nf6 4. Nf3 a6 5. Nc3 Bf5 6. Nh4

White would like to get the pair of bishops and some space advantage on the kingside. (6. Qb3 Also a strong move to attack the b7 and d5 pawns.) 6... Bg4 7. Qb3 b5 8. cxb5

(8. cxd5 This move was better, it allows white to attack the b5 pawn with

a2-a4. cxd5 9. h3 Bc8 (9... Bh5 it is a mistake. It gives time for white to

advance the g-pawn. 10. g4 Bg6 11. Nxg6 hxg6 12. g5 Ne4 13. Qxd5 White wins the pawn.) 10. a4 b4 11. Qxb4 Nc6 12. Qb3 Rb8 13. Qd1 g6 14. Bd3 Bg7 15. O-O

O-O White has a small advantage, black has compensation for the pawn.) 8...axb5 9. h3 Bh5 10. g4 Bg6 11. Nxg6 hxg6 12. Bg2 e6 13. Bd2 Nbd7

The black knight goes to the nice outpost on c4. 14. O-O (14. Qc2 Nb6 15. b3 It was better to prevent Nc4.) 14... Nb6 15. a4

White would like to open the position, because he has bishops and development advantage. Nc4 16. Bc1 Bd6 Black planned to capture on g4. 17. f3 It is too slow (17. e4 gives a wild game. Nxg4 18. exd5 cxd5 19. Re1 Nxf2 20. Kxf2 Qh4+ 21. Ke2 bxa4 Black has counterplay for the piece, because of the situation of the white king and 2 extra pawns.) 17... Bc7 (17... Qb6 18. Qc2 O-O 19. b3 Na5 20. axb5 cxb5 21.Qd3 Nxb3 22. Rxa8 Rxa8 23. Nxb5 Nxc1 24. Rxc1 around equal.) 18. Qc2

Strong move. White wants to push back the knight with b2-b3.

18... Qd6 19. f4 g5 (19... b4 Black should play more solid to get an equal position. 20. Ne2 O-O 21. b3 Na5

22. Bd2 Bb6 with c6-c5 to equalize.) 20. b3 Nb6 21. Bd2 (21. a5 I was thinking about this move in the game, but I thought the a-pawn can be weak instead of strong. 21..Nbd7 22. a6 O-O black will get counterplay with b4 and c5.) (21. Rf2 Gives space for the king on f1 and plans fxg5.21... gxf4 22. e4 Strong move to attack the center. 22...dxe4 23. Bxf4 Qd8 24. Bxc7 Qxc7 25. Nxe4 Nxe4 26. Bxe4 O-O Black has counterplay against the white king.) 21... gxf4 22. exf4 bxa4 23. Nxa4 Nxa4 24. bxa4 Ne4 25. Be3 f5 26. a5

This was a critical move. I decided to sacrifice the pawn to open the a-file and the a4 square for the queen to eye on the black king. 26...fxg4 (26... Bxa5 27. Ra4 I wanted to double the rooks to attack the pinned bishop. Kf7 28. Rfa1 Qc7 29. R1a3 (29. Qa2 not works because of Nc3 fork) 29... Ra7 30. Bxe4 fxe4 31.Qa2 Rha8 Defends. Black is better, because the d4 and f4 are fixed on the bishop's colour.) 27. hxg4 Rh4 28. a6

I decided to sacrifice the g4 pawn,because the a-pawn will be strong and the c6 pawn will be a target. 28...Rxg4 29.a7 g5 The position is in dynamic balance. 30. Ra6 I wanted to break in from

the side. gxf4 (30... Kd7 31. Rc1 Ba5 32. Rxa5 gxf4 33. Bxf4 Rxf4 {black has

enough counterplay to get equal position.}) 31. Rxc6

f3 - The losing move. Black opens the diagonal for the queen, but the white king can escape easily.(31... Qa3 The black queen comes from the other direction to attack the e3 bishop. 32. Rxe6+ Kd8 33. Bc1 Qxa7 34. Rxe4 dxe4 35. Qxe4 Bd6 36. Qd5 Rxg2+

37. Kxg2 Qg7+ 38. Kh1 Qh6+ 39. Kg2 Qg6+ 40. Kh1 Qh6+ Draw.) 32. Rxf3 (32.Rxd6 Black wanted to play this line. Rxg2+ 33. Qxg2 fxg2 34. Rxe6+ Kd7 35.Rf7+ Kxe6 36. Rxc7 Nd6 37. Kxg2 Nc8 38. Kf3 Nxa7 Equal.) (32. Rxc7 Qxc7 33. Qxc7 Rxg2+ 34. Kh1 Ng3+ 35. Qxg3 Rxg3 black wins.) 32... Qh2+ 33. Kf1 Ng3+ 34. Rxg3

(34. Ke1 I calculated this too, but I was not sure if it wins. It

looked more risky. Ba5+ 35. Kd1 Black has no good checks and the white rooks and queen is ready to checkmate. Ne4 36. Rxe6+ Kd7 37. Qc6+ Kd8 38. Re8#) 34... Qxg3 35. Rxc7 Qxe3

I played one more move and black resigned. Can you find the move?