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Here is a chess position to be solved. It is technically illegal, but for the sake of the puzzle, we'll ignore that. Find the plan for White that wins the game, with proper reasoning.

enter image description here

FEN: 1rkr1b1b/2p1pKp1/1pPpP1Pp/3P1p1P/1P3p2/3pp3/8/R1B4N w - - 0 1

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    $\begingroup$ I don't think the black bishop on h8 has any purpose. You could probably remove it to make the position less ugly and slightly less illegal. $\endgroup$
    – Evargalo
    May 3 at 13:08
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    $\begingroup$ It acts as a red herring for the computers and humans as well. Stockfish without h8 bishop solves this puzzle within a minute compared to taking almost 20 minutes. $\endgroup$
    – I'm Nobody
    May 3 at 18:18

1 Answer 1

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White can win with the move

b5, to prevent black from playing b5

Then, if black plays d2, white plays

Bxd2, then whether black plays exd2 or e2, white plays Nf2 blocking the f file. In one case the knight also stops the d pawn from queening, and in the other case the bishop stops the e pawn from queening.

If black plays e2 first, then white plays

Bd2, blocking the d-file and guarding e1. The white knight will soon jump to f2 to block the f file.

If black plays f3, then white plays

Bxe3, then if black plays f4, white plays Bxf4, or if black plays f2, then white plays Bxf2 or if black plays d2, then white plays Bxd2.

The general strategy is to

keep the rook on the a-file and force zugzwang after black moves all of his pawns to their deaths or until they have no more moves.

If black plays Ra8, white plays

Rxa8 checkmate.

If at any point black plays Rb7, white plays

Ra8, forcing black to block with his rook, then white plays Ra7. Now if black plays Rb7 again, white takes it with the rook unless that would be stalemate. If it would be stalemate, then cxb7, and after Kb8, then Ra8, Kb7. Now if the rook is still on d8, Rxd8, else Rd8. If black's c-pawn moves, white takes it with the d-pawn (so black's b pawn can never get rolling). At this point, the black king has no way to stop Rxf7 and Kxe7 in order to queen the e6 pawn, especially with the help of the rook.

If black plays Rd7,

white takes it with the e pawn

If black plays Re8,

white takes it with the king

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  • $\begingroup$ Nailed it. Perfect solution. Surprisingly, stockfish at depth 50 does not find a solution to this seemingly decent puzzle. $\endgroup$
    – I'm Nobody
    May 2 at 18:15
  • $\begingroup$ @I'm Nobody Not surprising, but I bet Alpha Zero would immediately see it $\endgroup$
    – JLee
    May 2 at 18:19
  • $\begingroup$ Already upvoted this correct answer couple of Days ago, but now I think this requires a small correction. With all the pawns gone and Re8 taken by the king : "Now if black plays Rb7 again, white takes it with the rook" ; This will be a stalemate ; Here the Pawn must be used to take the Rook, then Black has Kb8 and White should try Ra8 and then take the Bishop(s) and Promote the Pawn(s) to Queen(s). $\endgroup$
    – Prem
    May 13 at 6:36
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    $\begingroup$ @Prem Thanks for pointing that out. I updated the answer to accommodate that scenario. $\endgroup$
    – JLee
    May 13 at 13:33

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