A blunder can ruin a nearly-winning position. So can two lesser errors.
Evgeny Pigusov White
Gabor Berenyi Black
Budapest 1989
Queen Pawn’s Game D02
1 ♘f3 d5 2 g3 ♘c6 3 d4 ♗f5 4 ♗g2 ♕d7 5 c4!
Black would be at least equal after 5 0-0 0-0-0 6 c4 dxc4! because he gets pressure on d4 (7 ♗e3 e5 or 7 e3 e5).
5...dxc4 6 ♘c3 0-0-0 7 d5! ♘b4!
Now 8 0-0 would set a trap, 8...♘xd5? 9 ♘xd5 ♕xd5 10 ♕xd5 ♖xd5 11 ♘g5 and White wins material. But 8...e6 9 e4 ♗g6 remains muddy.
8 ♘e5 ♕e8 9 e4! e6!
Black must blast the center before White pushes him back (9...♗g6? 10 a3!). Now 10 exf5? exd5 is good for him (11 f4 f6 or 11 ♕e2 ♕xe5).
10 a3 exd5?
Question 273: What was better?
11 axb4 ♕xe5?
Still unclear is 11...dxe4! 12 ♕a4 ♕xe5 13 ♕xa7 ♘f6.
12 ♖xa7 ♘e7
Or 12...♔b8 13 ♕a4 with a threat of ♖a8 mate.
13 ♗f4 ♕e6 14 0-0!
On 14...♗g6, White wins with 15 exd5, among others.
14...♗g4 15 exd5! resigns.
The end was 15...♗xd1 16 ♖a8+ ♔d7 17 dxe6+ or 15...♕g6 16 ♕a4.
Mario Sibilio White
Spyridon Skrembris Black
Rome 1983
1 ♘f3 ♘c6 2 d4 d5 3 g3 ♗f5 4 ♗g2 ♕d7 5 c4 dxc4 6 d5 0-0-0 7 ♘c3 ♘b4 8 ♘e5 ♕e8 9 e4! e6! 10 a3 exd5 11 axb4 dxe4! 12 ♕a4 ♕xe5 13 ♕xa7 ♗xb4?? 14 ♕a8+ ♔d7 15 ♕a4+! b5 16 ♕xb4 ♖b8 17 0-0 ♘e7 18 ♖d1+ ♔c8 19 ♗f4 ♘c6 20 ♕a3 ♕e6 21 ♕a6+ ♖b7 22 ♖d6! ♕xd6 23 ♗xd6 and wins.