Black to move. My computer gives the evaluation -2.5 but I can't find the winning sequence for black.
[FEN "6k1/6pp/4p3/3pP3/2pP1PP1/1p6/1K5P/8 b - - 0 1"]
(Black goes up the board)
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Sign up to join this communityBlack to move. My computer gives the evaluation -2.5 but I can't find the winning sequence for black.
[FEN "6k1/6pp/4p3/3pP3/2pP1PP1/1p6/1K5P/8 b - - 0 1"]
(Black goes up the board)
If we look at the position we see a number of things:
That said let's look at some sample lines starting with what happens if black allows an immediate f5 by white:
[FEN "6k1/6pp/4p3/3pP3/2pP1PP1/1p6/1K5P/8 b - - 0 1"]
1...Kf7 2. f5 Ke7 3. fxe6 Kxe6 {and both side have their king's tethered to the opponent's passed pawn(s).
So, to have any chance of winning black's first move is forced: g6 to stop the immediate f5. Black then also needs to restrain white's kingside majority enough so that black has enough time to get the king to b4 and be able to force one of the pawns through before white can queen a pawn.
After g6 the other key move for black is h5. The idea is fix the white pawns into a slower structure (white pawn on g5) or a losing structure where the black king can enter on f5 because the g pawn has been lured away by taking the h5 pawn.
[FEN "6k1/6pp/4p3/3pP3/2pP1PP1/1p6/1K5P/8 b - - 0 1"]
1...g6 2. Ka3 Kf7 3. Kb2 h5 4. g5 (4. h3 hxg4 5. hxg4 g5 {key move breaking up and taking the pawns or creating a new black passer} 6. f5 (6. fxg5 Kg6 7. Ka3 Kxg5 8. Kb2 Kxg4) exf5 7. gxf5 g4 {and the new passer runs home}) Ke7 5. Ka3 Kd7 6. Kb2 Kc6 7. Ka3 Kb5 8. Kb2 Kb4 9. f5 c3+ 10. Kb1 Ka3 11. fxg6 b2 12. Kc2 (12. g7 Kb3 13. g8=Q c2#) Ka2 13. g7 b1=Q+ 14. Kxc3 Qb8
Stockfish gives -8 on Lichess, analysis.
And the reason is very simple actually. b and c pawns are protected passed pawns which means the white king cannot leave there. If it leaves, you will promote. So their king is stuck there and you are pretty much free with your king to collect all pawns. There are multiple winning lines but I will leave here a little bit complicated one:
[FEN "6k1/6pp/4p3/3pP3/2pP1PP1/1p6/1K5P/8 b - - 0 1"]
1... g6 2. h4 h5 3. g5 Kf7 4. Kc3 Ke7 5. Kb2 Kd7 6. Kc3 Kc6 7. Kb2 Kb6 8. Kc3 Kb5 9. Kb2 Kb4 10. f5 c3+ 11. Kb1 Ka3 12. fxg6 b2 13. g7 Kb3 14. g8=Q c2#
I don't know, the first thing I looked at was an immediate ... h5. It looks like on any reply you're creating a passed pawn while your king holds off the white pawns. If he plays h3 you take and play g5 like in one of the other sub-variations.