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In today's chess.com daily puzzle, I have no idea why the first move of the solution makes sense.

[fen "8/8/8/pp6/P7/7K/1k6/R7 w - - 0 1"]

The first step in the suggested solution is Ra3. I do not see how that beats axb5 (which is the second move anyway).

Can anyone explain why to me?

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  • If you're a premium member (gold will do), the accompanying video explains the puzzle. (Strictly an FYI, I'm not schilling for chess.com.)
    – GreenMatt
    Feb 7, 2022 at 4:54

1 Answer 1

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10

If you play out the moves you will see that axb5 leads to a draw because white can never drive the black king away from the pawn with just the queen and using the king leads to stalemate or black also queening. Rxa3 leads to a win because white queens with check and the black pawn can never get to a2 creating stalemate chances.

[fen "8/8/8/pp6/P7/7K/1k6/R7 w - - 0 1"]

1. Ra3 (1. axb5 Kxa1 2. b6 a4 3. b7 a3 4. b8=Q a2 5. Qh8+ {any king move is stalemate} Kb1 6. Qh7+ Ka1 7. Qg7+ Kb1 8. Qg6+ Ka1 9. Qf6+ Kb1 10. Qf5+ Ka1 11. Qe5+ Kb1 12. Qe4+ Ka1 13. Qd4+ Kb1 14. Qd3+ Ka1 15. Qc3+ Kb1 16. Qb3+ Ka1) Kxa3 2. axb5 Kb2 3. b6 a4 4. b7 a3 5. b8=Q+ Ka1 {Kc2 is the same White threatens the pawn and black must defend} 6. Qe5+ Kb1 7. Qe4+ Kb2 (7...Ka1 8. Qc2 a2 9. Qc1#) 8. Qb4+ Ka2 9. Kg2
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  • 2
    Fascinating, i would never have seen that. Thank you got satisfying my curiosity and providing me with such a great answer!
    – Lot
    Feb 5, 2022 at 13:50
  • 2
    A reasoning that helped me understand is the following: with respect to the "main variation" where everyone pushes their pawns, white loses one tempo with Ra3, but this move causes black to lose two: the black king needs to be removed from the a-column where it blocks the a-pawn, and then moved once again when white promotes with check.
    – Federico Poloni
    Feb 5, 2022 at 21:31
  • Out of interest, how quickly do very good players 'see' this? And would many get caught out (i.e. to a layperson axb5 looks obviously winning, since white queens so quickly) - would this catch out some good players?
    – stevec
    Feb 6, 2022 at 2:42
  • 3
    @stevec A good player would calculate up to 4. ... a2 and know that this position is a draw, because they learned this while studying queen and pawn endgames. Then they'd look for a way to move the black king away from the corner before pushing their pawn. I would almost definitely miss this in a game, but I'm not a good player.
    – Edward
    Feb 6, 2022 at 3:51
  • But 9. Qf6+ Kb2 is an illegal move.
    – user31965
    Feb 28, 2022 at 14:58

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