Sacrifice de cavalier en f4

   [Event "St Petersburg All Russian"]  [Site "St Petersburg"]  [Date "1909.."]  [Round "6"]  [White "Tereshchenko, Nikolay Semenovich"]  [Black "Alekhine, Alexander"]  [Result "0-1"]  [ECO "A43"]  [PlyCount "60"]  [EventDate "1909.02."]  [EventType "tourn"]  [EventRounds "17"]  [EventCountry "RUS"]  [Source "ChessBase"]  [SourceDate "1999.07.01"]   1. d4 e6 2. c4 c5 3. d5 e5 4. Nc3 d6 5. e4 Nd7 6. Bd3 a6 7. Nf3 Be7 8. O-O g5  9. Be3 Nf8 10. Qd2 h6 11. Ne1 Ng6 12. f3 Nf6 13. Rc1 Bd7 14. a3 b6 15. Kh1 Nh5  16. g3 Bh3 17. Nc2 Bxf1 18. Rxf1 Qd7 19. Qf2 Qh3 20. Ne1 Ngf4 21. gxf4 gxf4 22.  Bd2 Rg8 23. Ng2 Bh4 24. Nd1 Bxf2 25. Rxf2 Rg5 26. Kg1 Ke7 27. Bf1 Rag8 28. Nc3  Ng3 29. hxg3 Rh5 30. Re2 fxg3 0-1   

   [Event "St Petersburg All Russian"]  [Site "St Petersburg"]  [Date "1909.."]  [Round "6"]  [White "Tereshchenko, Nikolay Semenovich"]  [Black "Alekhine, Alexander"]  [Result "0-1"]  [ECO "A43"]  [Annotator ",oraziopuglisi@gmail."]  [SetUp "1"]  [FEN "r3k2r/4bp2/pp1p2np/2pPp1pn/2P1P3/P1NBBPPq/1P3Q1P/4NR1K b kq - 0 20"]  [PlyCount "21"]  [EventDate "1909.02."]  [EventType "tourn"]  [EventRounds "17"]  [EventCountry "RUS"]  [Source "ChessBase"]  [SourceDate "1999.07.01"]   20... Ngf4 $1 {Et voilà classique !} 21. gxf4 $2 (21. Bd2) 21... gxf4 {On voit  ici le gain de temps sur le Fe3 ! Un temps qui permettra le coup très fort 22..  .Rg8} (21... exf4 {Bcp moins intéressant car la colonne g ne s'ouvre pas !})  22. Bd2 Rg8 23. Ng2 Bh4 (23... Ng3+ {Gagne aussi !}) 24. Nd1 $4 (24. Qxh4 $4  Qxg2#) (24. Nxh4 Ng3+ 25. Kg1 Nxf1+ 26. Ng2 Nxh2) 24... Bxf2 25. Rxf2 Rg5 26.  Kg1 Ke7 27. Bf1 Rag8 28. Nc3 Ng3 29. hxg3 Rh5 30. Re2 fxg3 0-1