Karpov,An (2700) - Kavalek,L (2625) [B36] Nice ol (8), 1974
[GM Lubomir Kavalek/ Huffington Post]

For the first 29 moves Karpov and I fought tooth and nail and we reached this position. Black's game is solid and the bishops of opposite colors give it a drawing flavor. The only loose pawn on a6 can be protected easily. Karpov finds a way to improve his position and create winning chances.

30.h6 Bf8
Keeping the pawn h6 under observation.

[Karolyi devotes six pages to 31.g5 The move locks the kingside, protects the h-pawn, but it is not easy to envison how white could break through. Anyway, Karolyi shows the winning ways and concludes that white's king move is the only inaccuracy Karpov made during the entire game.]

31...fxg4 32.Bxg4 Kf7 33.Be6+ Kf6 34.Bg8
[White was able to dribble his bishop to g8, attacking the h-pawn. After 34.Kb4 a5+ 35.Kb3 Rc7 36.a3 g5 black is fine.]

[Surprisingly, the computer engines suggest a pawn sacrifice as the way out. After 34...e6 35.Bxe6 (35.dxe6 Rh5= ; 35.Bxh7 exd5 36.Rg1 (36.Bg8 Bxh6! 37.Rxh6 Kg7=/+ ) 36...Rxc4+ 37.Kd3 Rxf4 38.Rxg6+ Kf7 the white pieces stumble against each other.) 35...a5 36.Kb3 Rc7 37.Ka4 Rxc4+ 38.Kxa5 Be7 white still has some chances. (After 38...Rxf4 39.a4 the passed a-pawn is dangerous.) ]

35.Bxh7 e6 36.Bg8 exd5 37.h7
[37.Bxd5 Rh7= ]

[37...Rxc4+! 38.Kd3 (Better seems 38.Kb3 Bg7 39.Bxd5 Rc8 40.Be4 threatening 41.Rg1.) 38...Bg7 39.h8Q?! (39.Bxd5 would be the only try to win, but after 39...Rc5 40.Ke4 Bh8 41.Rg1 Rb5+/= black has some chances to hold.) 39...Bxh8 40.Rxh8 and I missed the backward rook move 40...Rc8! threatening 41...Kg7, black draws. (But not 40...Kg7 41.Bxd5 Rc5 42.Rg8+ Kh7 43.Be6 wins.) ]

38.Bxd5 Bh8 39.Kd3 Kf5 40.Ke3 Re7+ 41.Kf3 a5 42.a4 Rc7 43.Be4+ Kf6 44.Rh6 Rg7
[Unfortunately, 44...Kg7 45.Rxg6+ Kxh7 46.Rg1+ Kh6 47.Rh1+ Kg7 48.Rh7+ drops a rook.]

Black is in zugzwang and must lose the pawn on g6. 1-0