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In this Lichess puzzle, after the initial moves

[title "Black to move"]
[fen ""]
[Startply "17"]
[StartFlipped "1"]

1. c4 b5 2. cxb5 Bb7 3. Nf3 g5 4. Nxg5 Bg7 5. Nf3 c5 6. Nc3 a6 7. d4 axb5 8. Nxb5 Qa5+ 9. Nc3 Bxf3!

Why can the bishop just take the knight? Why is it so bad for white to retake on f3?

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7
  • 1
    1. if you play Bxf3 first then exf3 opens up the f1 bishop guarding the b5 knight. so Qa5 doesnt work anymore due to Bd2. 2.if Qa5 first the Nc3 is forced because otheriwise it is hanging. Now if Bxf3 white doesnt really have a choice other than to take back. then a defender is removed from d4 so black can take cxd4 and win the c3 knight due to pin
    – cmgchess
    Mar 4, 2022 at 12:09
  • If white takes bishop, theb b cxd4 and taking the knight next move
    – Arctic Char
    Mar 4, 2022 at 12:16
  • 1
    The meaning of my question seems to have got lost during editing (now restored). I didn't want to give the puzzle away, but I was apparently not clear enough initially.
    – hkBst
    Mar 4, 2022 at 15:29
  • @cmgchess, you would think that taking back the bishop was a no-brainer, but the computer thinks it is very bad to do that (with either pawn). The computer thinks the solution is to take the knight and then for white to play Bd2, and then black can move its bishop away. If you take on f3 then the eval goes down more than 3 points!
    – hkBst
    Mar 4, 2022 at 15:37
  • @hkBst i mean even if he didnt take back and played Bd2 he'll be down a piece for no compensation after black retreats the bishop.
    – cmgchess
    Mar 4, 2022 at 15:48

3 Answers 3

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10

Here's why:

[FEN "rn2k1nr/1b1pppbp/8/q1p5/3P4/2N2N2/PP2PPPP/R1BQKB1R b KQkq - 1 1"]

1...Bxf3 2. exf3 cxd4 3. Bd2 (3. Qxd4 Bxd4) dxc3 4. bxc3 Bxc3 5. Rc1 Bxd2+ 6. Qxd2 Qxd2+ 7. Kxd2 Rxa2+ 8.Ke3 Nc6

White is completely lost.

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  • 3
    True. I can relate to the OP's confusion though: lichess puzzles are often the most puzzling in where they stop and consider it done - sometimes you would just play the move that feels right and it says "congratulations, you won!" all while you sit there stumped.
    – Lodinn
    Mar 4, 2022 at 20:16
  • 4
    @Lodinn: For those of us with lower ratings, there's also the problem that in our practical experience, a "good" move is a move which is not a blunder, rather than an actual good move.
    – Kevin
    Mar 4, 2022 at 20:41
  • 5
    @Lodinn sometimes it feels like it's saying "yes you get the idea, no need to make you play out the rest of the obvious moves" which in my experience is correct maybe 50% of the time
    – llama
    Mar 4, 2022 at 23:07
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    @llama I think that more often, it's really saying "Yes, now there's a few ways to win from here, but we have a strict requirement that there is exactly one correct solution to our puzzles so the puzzle must end here"
    – Edward
    Mar 5, 2022 at 4:36
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    Subtract one point for not taking a2 with check before Nc6 :-)
    – Hauke Reddmann
    Mar 5, 2022 at 8:38
8

After retaking the bishop, Black will take on d4 with his pawn, attacking the pinned knight. White can do nothing to stop Black from capturing it "for free" on the next move.

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7

After you complete the puzzle, " Stockfish 14+NNUE in local browser" appears in the upper right (just above the list of moves), and a toggle button appears to the right of that. If you click it, it will suggest the continuation 10. Bd2, but you can play around with other lines by making those moves on the board. For instance, after 10. gxf3, the engine recommends 10. ... cxd4. As it has been captured, the knight is not available to capture the pawn, and the queen is deterred by the bishop on g7. As the knight is pinned, it can't be moved away.

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