Why is pawn c6 is not winning here and what is the missed win for black?

Question

When I played a game on chess.com and then ran the analysis afterward, the computer said that the pawn move c6 was incorrect.

 [title "Black to play"]
 [fen "r1b2rk1/p1p2p1p/5p2/2bNq3/8/8/PPP1BPPP/R2Q1RK1 b - - 0 1"]
 [startflipped "0"]

 1... c6

I don't understand why the move is considered a missed win. Can anyone explain why?

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user1583209 · Accepted Answer · 2020-03-13 17:18:34Z

14

Look at the diagram. The engine tells you the best move (Rd8).

The idea behind that move is that it pins the white knight to the queen and at the same time attacks the knight a second time.

Moving the knight white would lose the queen (for a rook).
If white tries to defend the knight (with c4, Bc4 or Bf3), black would play c6 attacking the pinned knight with a pawn.

So the idea is: first pin, then win the knight with c6.

If you play c6 first, white could just retreat the knight to c3.

It is worth memorizing this theme (pin a piece, then attack it again) as it is quite common. Also works with diagonal pins by queen/bishop.

answered Mar 13, 2020 at 16:44

user1583209

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One thing I would add is that Rd8 comes with tempo since it contains an immediate threat. Threat defend, then new threat with c6, and wins.
– PhishMaster
Mar 14, 2020 at 1:36
3

An important tactical point is that the knight can move away with check to f6 or e7. The rook is not protected after Rd8, so white might hope to play Qxd8 after black responds to the check, but black can capture the knight with the queen and protect the rook.
– Ross Millikan
Mar 14, 2020 at 2:16

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