When your opponent varies from the move you expect, it’s easy to shrug it off.
It’s harder to go to work.
Istvan Bilek White
Florin Gheorghiu Black
Bucharest 1968
Sicilian Defense, Closed Variation B25
1 e4 c5 2 ♘c3 ♘c6 3 g3 g6 4 ♗g2 ♗g7 5 d3 d6 6 f4 e5 7 ♘h3!? ♘ge7 8 0-0 0-0?
“What’s he thinking?” Black should have asked after ♘h3. The knight usually goes to f3 or e2.
9 f5!
One difference (from ♘f3) is that the f1-rook supports 10 f6!.
9...gxf5 10 exf5
Now 10...f6 11 g4 is awful (11...d5 12 ♘e2 and ♘g3-h5).
10...♗xf5
Another difference is that White’s queen gets to h5 quickly (10...♘xf5 11 ♕h5! prepares ♖xf5, ♗e4 or ♘d5, e.g. 11...♘fd4 12 ♘g5!).
11 ♖xf5! ♘xf5 12 ♗e4
A third difference is that this bishop joins the attack faster than if a knight were on f3 (12...♘cd4 13 ♕h5 ♕d7 14 g4 wins).
Question 210: What about 13...♕f6 ?
12...♘fd4 13 ♕h5
The kingside has no defense (13...f5 14 ♗d5+ ♔h8 15 ♘g5 h6 16 ♕g6!).
13...♖e8 14 ♕xh7+ ♔f8 15 ♗g5 ♕d7
A quick mate follows 15...f6 16 ♗h6 ♗xh6 17 ♕xh6+.
16 ♘d5 ♖e6 17 ♖f1 ♘xc2 18 ♗g6 ♘2d4 19 ♗h6 resigns.
Christian Gabriel White
Jan Smejkal Black
Altensteig 1990
1 e4 c5 2 ♘c3 ♘c6 3 g3 g6 4 ♗g2 ♗g7 5 d3 d6 6 f4 e5 7 ♘h3 ♘ge7 8 0-0 ♘d4! 9 ♗e3 0-0 10 g4 exf4 11 ♘xf4 ♖b8 12 ♗f2 ♘ec6 13 h3 b5 14 ♘cd5 b4 15 ♗g3 ♘e6 16 ♖b1 ♗b7 17 ♕d2 ♘cd4 18 c3 ♘xf4 19 ♘xf4 ♘c6 20 ♔h1 ♗c8 21 ♖f2? bxc3 White resigns.