In the second game of the 1987 World Championship, Kasparov played an English opening. In the ninth move Karpov played a novelty that he had prepared for his 1981 match with Korchnoi (the usual play is 9. ... exf3). It is claimed that Kasparov's next two moves, 10. d3 and 11. Qb3 completely refute Karpov's surprise move, but in the end Kasparov lost this game (it is the famous one in which he forgot to hit the clock after playing his 26th move).
Then in the fourth game, Kasparov plays an English again and reaches the same position up to move 8! Clearly it was a provocation, but whether he could refute 9. ... e3 or not was not demonstrated, because Karpov avoided it and played the usual 9. ... exf3, only to get trounced (incidentally, this was the 100th championship game between the two).
What is the novelty about, and how do Kasparov moves refute it?
For reference, here are the two games:
[Event "World Championship Game 2"]
[Site "Seville, Spain"]
[Date "1987.10.14"]
[Round "2"]
[Result "0-1"]
[White "Kasparov"]
[Black "Karpov"]
[ECO "A29"]
[FEN ""]
1. c4 e5 2. Nc3 Nf6 3. Nf3 Nc6 4. g3 Bb4 5. Bg2 O-O 6. O-O e4 7. Ng5 Bxc3 8. bxc3 Re8 9. f3 e3 10. d3 d5 11. Qb3 Na5 12. Qa3 c6 13. cxd5 cxd5 14. f4 Nc6 15. Rb1 Qc7 16. Bb2 Bg4 17. c4 dxc4 18. Bxf6 gxf6 19. Ne4 Kg7 20. dxc4 Rad8 21. Rb3 Nd4 22. Rxe3 Qxc4 23. Kh1 Nf5 24. Rd3 Bxe2 25. Rxd8 Rxd8 26. Re1 Re8 27. Qa5 b5 28. Nd2 Qd3 29. Nb3 Bf3 30. Bxf3 Qxf3 31. Kg1 Rxe1 32. Qxe1 Ne3 0-1
[Event "World Championship Game 4"]
[Site "Seville, Spain"]
[Date "1987.10.19"]
[Round "4"]
[Result "1-0"]
[White "Kasparov"]
[Black "Karpov"]
[ECO "A29"]
[FEN ""]
1. c4 Nf6 2. Nc3 e5 3. Nf3 Nc6 4. g3 Bb4 5. Bg2 O-O 6. O-O e4 7. Ng5 Bxc3 8. bxc3 Re8 9. f3 exf3 10. Nxf3 Qe7 11. e3 Ne5 12. Nd4 Nd3 13. Qe2 Nxc1 14. Raxc1 d6 15. Rf4 c6 16. Rcf1 Qe5 17. Qd3 Bd7 18. Nf5 Bxf5 19. Rxf5 Qe6 20. Qd4 Re7 21. Qh4 Nd7 22. Bh3 Nf8 23. R5f3 Qe5 24. d4 Qe4 25. Qxe4 Rxe4 26. Rxf7 Rxe3 27. d5 Rae8 28. Rxb7 cxd5 29. cxd5 R3e7 30. Rfb1 h5 31. a4 g5 32. Bf5 Kg7 33. a5 Kf6 34. Bd3 Rxb7 35. Rxb7 Re3 36. Bb5 Rxc3 37. Rxa7 Ng6 38. Rd7 Ne5 39. Rxd6 Kf5 40. a6 Ra3 41. Rd8 Ra2 42. Rf8 Ke4 43. d6 Nf3 44. Rxf3 Kxf3 45. Bc6 1-0