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Inspiration

BCLC guessed (see link) that even only 2P can win against Q, even if the Q side has the move, if they are advanced far enough. I quickly checked a few promising position candidates in a tablebase. He is correct, but even more, it is not even true that both pawns have to be on the 7th rank for that! Thus, a little challenge: Find the (at 1st look) unbelievable position where

  • White has K+Q
  • Black has K+P+P
  • White has the move but is lost
  • White is not in check
  • One black pawn is only on the 5th row (from White).

Sidenote A: The position might be unique (I guess but I'm not 100% sure). Sidenote B: Due to 50 move rule, the win is longer than the simple shortest mate, but won it is.

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1
  • Sidenote C: Just for fun, 3P can win even if none is on the 2nd rank and no imminent checks exist: Pa3 b3 c3 Kb2 wins against almost any.
    – Hauke Reddmann
    Commented Dec 15, 2021 at 18:22

2 Answers 2

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6

After fiddling around for a while with the Syzygy endgame tablebase, I found this position:

[Title "KQ vs. KPP, white is not in check"]
[FEN "3Q4/8/8/2p4K/8/8/2kp4/8 w - - 0 1"]

According to the tablebase, it's mate in 105 against best play by White, which starts with either Qa8 or Kg6. White can't stop promotion without sacrificing the Queen, and because Black is threatening to promote with check, the resulting KQP vs. KQ endgame is winning for Black.

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  • 1
    Ah, so even with "no check" it's not unique, I already feared that. My position was Ka4 Qa2/Ke1 Pd2 Pe5 with a central pawn remaining. Didn't expect a bishop pawn would work too. (And maxima mea culpa to wimi!)
    – Hauke Reddmann
    Commented Dec 13, 2021 at 8:22
  • Hauke: I have heard that bishop pawns are the most likely to win the QvQ endgame.
    – Ferazhu
    Commented Dec 13, 2021 at 17:05
4

Of course, letting the White king be in check at the beginning seems to be a reasonable approach. Here is a position with a Black pawn on the fifth rank (its fourth rank):

[Title "KQ vs KPP: White to move loses"]
[FEN "Q7/8/8/5p2/8/8/4pk2/3K4 w - - 0 1"]

It is not unique: here is another one:

[Title "KQ vs KPP: White to move loses"]
[FEN "Q7/8/8/4p3/8/8/4pk2/3K4 w - - 0 1"]

and there is even one with a Black pawn on the sixth rank (its third rank)!:

[Title "KQ vs KPP: White to move loses"]
[FEN "Q7/8/5p2/8/8/8/4pk2/3K4 w - - 0 1"]
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  • I upvoted but wK in check is a bit of cheating :-) I edited my question to avoid this. (If noone else bites I accept the answer but please please try harder :-)
    – Hauke Reddmann
    Commented Dec 12, 2021 at 19:08
  • @HaukeReddmann with no wK in check, I have only achieved third rank until now...
    – wimi
    Commented Dec 12, 2021 at 19:11

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