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I was just reviewing my game and was wondering why the AI would think this is the best move. All I see is giving white a free knight.

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    Did you look at what the engine lines say?
    – qwr
    Jul 27, 2023 at 4:20
  • When adding a diagram style question, it's always nice to add the FEN or a diagram. The FEN you're looking for is [FEN "r1bq1rk1/4bppp/ppnp1n2/2p1p1B1/4P3/P1NP1P2/1PP1N1PP/R2QKB1R b KQq - 0 1"]
    – IT M
    Jul 27, 2023 at 11:30

1 Answer 1

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10 . . . Nxe4 is best because it wins a pawn, while other moves only keep material equality (or worse, give away material).

The move is a typical "desperado" sacrifice, introducing a line where wB and bN try to take as much material as possible before being captured themselves:

11 Bxe7 (or 11 Nxe4 Bxg5 and if then 12 Nxg5 Qxg5)
11 . . . Nxc3! (not Qxe7? 12 dxe4 1-0)
12 Bxd8 (or 12 dxe4 Qxe7)
12 . . . Nxd1 (certainly not Rxd8?? and Black is down a Queen)
13 Rxd1 Rxd8 and Black remains a pawn up.

At the end White can instead play 13 Bxb6 Nxb2, but Black is still up a pawn and the desperado Knight escapes while the Bishop is in danger, e.g. 14 Bc7 (trying to restore material equality) Na4 15 Bxd6 Rd8 16 Bc7 Rd7 and the Bishop is trapped and lost.

Note that the engine already has Black up 1.1 pawns after 10 . . . h5?!, and 1.67 pawns after Nxe4!. That's probably because White is behind on development and needs several moves to castle; that's less of an issue after the Queens come off the board, though meanwhile Black also gains B for N.

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    Clear and correct analysis. Might be more comprehensibe with a diagram perhaps? I added the FEN in the comment section of the question.
    – IT M
    Jul 27, 2023 at 11:44
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    Note that this motif is rather common. Encountered it myself. (Qd1 Nc3 Bg5 Pe4 vs Qd8 Be7 Nf6 is all you need to at least give it a calculation. It can fail because of the N landing on d1 and getting stuck, or whatever.) Jul 30, 2023 at 17:32

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