[Event "Yugoslavia-Switzerland"] [Site "?"] [Round "0"] [White "Pirc"] [Black "Christoffel"] [Result "1-0"] [ECO "A15"] [Opening "English: Anglo-Indian, 2.Nf3"] {Whether or not ot exchange the Knight} 1. c4 Nf6 2. Nf3 c6 3. d4 d5 4. e3 Bf5 5. Nc3 e6 6. Bd3 Bg6 7. Ne5 Nbd7 8. f4 Be7 9. O-O Qc7 10. Qc2 Bxd3 11. Qxd3 Rd8 12. Bd2 O-O 13. Rac1 {White is retaining all options - the best method of keeping a persistent initiative. He can 1) Being a Queensdie advance by Pb4 followed by eith Pc5 or Pcxd5 2) He can thrust Pe4 3) Bayonet attack by Pg4. All these opportunities arise mainly from the influence of the Knight on e5, and Black's main headache is to decide whether or not to take it off} 13... Nxe5 {He decides to cut the knot} 14. fxe5 dxc4 15. Qxc4 Nd7 $2 (15... Nd5 16. e4 (16. Ne4 f6 17. exf6 gxf6) 16... Nb6 17. Qd3 Qxe5) 16. Ne4 c5 {Black wants to prevent Bb4, with exchange of Bishops and subsequent occupation of d6 with the Knight, but he is jumping out of the frying pan into the fire} 17. Bb4 $1 { This forces ... Pb6, after which the Black knight cannot get into play via b6} 17... b6 18. Bc3 Qc6 19. dxc5 $1 Bxc5 (19... Nxc5 20. Nf6+ gxf6 21. exf6 Bd6 22. Qg4+) 20. Nxc5 Qxc5 (20... bxc5 21. b4 Rc8 22. Bd4 Qc7 23. bxc5 Nxe5 24. Qc3 f6 25. Bxe5 $16) (20... Nxc5 21. Bd4 (21. b4 Qe4 $1)) 21. Bd4 $1 { Thus White obtains control of the c-file by force, securing a great positional advantage} 21... Qc8 22. Qc7 Qa8 23. b4 { With the same idea as Bb4, depriving the Knight of available squares} 23... Qe4 24. Qc6 $1 Qd3 25. Qf3 Qb5 (25... Rc8 26. Rxc8 Rxc8 27. Qxf7+) 26. Rc7 a6 ( 26... Nxe5 27. Bxe5 Qxe5 28. Rxf7) 27. Qc6 Qxc6 {At last Whit e has his favourable ending. The rest, as they say, is a matter of technique} 28. Rxc6 Rc8 29. Rfc1 Rxc6 30. Rxc6 Rb8 31. Rc7 Rd8 32. Ra7 g6 33. Rxa6 Rc8 34. Ra7 Nf8 35. Bxb6 Rc4 36. Bc5 Kg7 37. a4 g5 38. Rc7 Re4 39. a5 Ng6 40. a6 1-0