I recently played a game featuring the Old Sicilian with a bit of a branch-off. White played 3. Bc4 after 2. Nf3 Nc6, which I don't deal well with. I ended up playing 12... d4, attacking the White knight, which the analysis later marked as a blunder. I'm not an advanced chess player, and I can't find out why this would be so.

[FEN ""]
[startply "23"]

1. e4 c5 2. Nf3 Nc6 3. Bc4 d6 4. O-O Nf6 5. d3 g6 6. Nc3 Bg7 7. b3 O-O 8. Bb2 Bg4 9. h3 Bxf3 10. gxf3 e6 11. f4 d5 12. Bb5 d4 13. Bxc6 dxc3 14. Bxb7 cxb2 15. Rb1 Rb8 16. Ba6 Nh5 17. Rxb2 Nxf4 18. Qf3 Qg5+ 19. Kh1 Bxb2 20. Rg1 Qe5 21. Rb1 Ba3 22. Qg3 c4 23. dxc4 Bd6 24. a3 Rb6 25. Bb5 Bxa3 26. Ra1 Bd6 27. Rxa7 Ne2 28. Qe3 Qh2#

Can anybody please can clue me in to how 12... d4 was a blunder?

  • 3
    Right, we'd rather have the PGN (or at least the FEN of the position in question.) The graphic goes by too fast.
    – D M
    Commented Apr 9, 2021 at 2:46
  • Thanks. I'll add it in a second... Commented Apr 9, 2021 at 3:14

3 Answers 3


Because black can play 12...Nd4 instead. The threat is to catch the bishop b5 with ...a6 and ...b5 and eventually ...c4. I do not see how white can prevent this. White loses a piece.

  • Why play ...c4? Commented Apr 9, 2021 at 4:51
  • 4
    Oh, I see, it's assuming white plays b4 to create an escape square for the bishop. Commented Apr 9, 2021 at 4:57
  • 1
    @Brian McCutchon exactly. Commented Apr 9, 2021 at 5:22
  • Interesting line. Even with 12...Nd4. 13. b4 a6 14. a4 b5 15. b3 c4 16. dxc4 and black knight is hanging, 16...dxc4 actually protects the knight again.
    – justhalf
    Commented Apr 9, 2021 at 11:46

Computers have a different idea of what the word "blunder" means than a human. To a computer a blunder is any move that changes the evaluation of the position in a bad way more than a pawn's worth, even if the reason is not obvious. To a human, a blunder is an obviously bad move.

So, your move is not really a blunder, it's just a missed opportunity. By playing Nd4 instead of d4, you would be threatening 13...a6 14. Ba4 b5 winning the bishop which is trapped. There is no way for White to escape this because if plays 13. b4 to try to make a luft for the bishop, then Black just plays 13...cxb4 and the White knight is under attack. If the knight moves, then the bishop is lost because the knight on d4 is attacking it.

This position is a good example of why you want to get your pieces out of attack and put pressure on the enemy pieces. Nd4! does both. It removes the knight from the bishop's attack and makes an attack of its own, two things at once.


because white plays Na4 and attacks the pawn at c5. Impossible to secure with b4 because the Knight will be lost after that.

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