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On a standard size chessboard, with white to move, make a configuration of chess pieces and moves, so that with every move by white the black king repeatedly becomes checked. With every move black must capture a white piece while escaping from check.

Any number of black or white pieces (Queen, Rook, Bishop, Knight, Pawn) can be used. Black and White king must be included on the board,

What is the most number of checks possible?

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    $\begingroup$ While I'm all about such a puzzle; this is likely to have many answers that arrive at the most number of checks, even with proof (e.g. the same configuration rotated 90 degrees). Also, what's preventing me from creating an endless chain where the king must "dance" in a square of checks with no hope of escape? $\endgroup$
    – Hazel へいぜる
    Commented Oct 4, 2021 at 16:00
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    $\begingroup$ The checking would definitely end since black captures on every move. $\endgroup$
    – TSLF
    Commented Oct 4, 2021 at 16:06
  • $\begingroup$ Ah, I misunderstood at first; while I see it in "When in check black can only capture the checking white pieces", others might not and may confuse it as I did for "black can only capture white pieces, black still blocks"; perhaps rephrasing to "When in check, black must capture a piece, and can only capture white pieces, per typical rules." would benefit others? $\endgroup$
    – Hazel へいぜる
    Commented Oct 4, 2021 at 16:23
  • $\begingroup$ Also, are we limited to the standard number of pieces or can we pull in additional pieces (e.g. an extra rook)? $\endgroup$
    – Hazel へいぜる
    Commented Oct 4, 2021 at 16:28
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    $\begingroup$ Needs Details or Clarity about what pieces are valid for the starting positions. Can I start with 40 Queens for example? $\endgroup$
    – Chris Cudmore
    Commented Oct 4, 2021 at 19:18

2 Answers 2

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With the "Use as many and any black or white pieces (both kings included)" restriction, the theoretical maximum becomes

61 checks and captures: there must be a square for both of the kings, and a target square for white's first move. The rest can be full of capturable white pieces.

Obviously, there can't be any legal position with that many white pieces, so we throw legality out of the window and start from here:

enter image description here
[FEN "PPPPPPPP/PPPPPPPP/PPPPPPPP/PPPPPPPP/PPPPPPPP/QPPPPPPP/QQPPPP1P/KQQQQRPk w - - 0 1"]

And as long as we are careful to eat the bottom two pawn rows in good order, we are good to go for the maximum:

enter image description here

For some strange reason, Lichess declines to do anything with this position, and chess.com won't let me copy paste the moves, so you get a screenshot of the board from one, and a screenshot of the moves from another. If you have a tool that works better, please drop a comment.

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  • $\begingroup$ 61 moves that captures to avoid check. no illegal moves $\endgroup$
    – TSLF
    Commented Oct 5, 2021 at 6:05
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Variation 1. position must be legal:

As there are at most 15 capturable white pieces this is a hard upper bound on the chain length.

This bound can

easily

be achieved.

Documentation:

[FEN "1N1k4/1QR2PPP/4P1n1/n2PN1r1/2P5/1P1BB3/P2R4/5K2 w - - 0 1"]
enter image description here`

1.h8=Q+ Nxh8 2.g8=Q+ Rxg8 3.Bg5+ Rxg5 4.Nbc6+ Nxc6 5.Qb8+ Nxb8 6.Rd7+ Nxd7 7.f8=Q+ Nxf8 8.Nf7+ Nxf7 9.e7+ Kxe7 10.d6+ Kxd6 11.c5+ Kxc5 12.b4+ Kxb4 13.a3+ Kxa3 14.Ra2+ Kxa2 15.Bb1+ Kxb1 *

Variation 2. position need not be legal:

I can do

60
initial position [FEN "kqBQBQBQ/1RRRRRRR/BRRRRRRR/BRRRRRRR/BRRRRRRQ/QRRRRRRR/BRRRRRRR/QRRRRQRK w - - 0 1"] 1. Ra7+ Qxa7 2. Rb8+ Qxb8 3. Ra7+ Qxa7 4. Rb8+ Qxb8 5. Ra7+ Qxa7 6. Rb8+ Qxb8 7. Ra7+ Qxa7 8. Rb8+ Qxb8 9. Ra7+ Qxa7 10. Rb8+ Qxb8 11. Ra7+ Qxa7 12. Rb8+ Qxb8 13. Ra7+ Qxa7 14. Bab7+ Qxb7 15. Ra6+ Qxa6 16. Bb7+ Kxb7 17. Qb6+ Qxb6 18. Rc7+ Qxc7 19. Rb6+ Qxb6 20. Rc7+ Qxc7 21. Rb6+ Qxb6 22. Rc7+ Qxc7 23. Rb6+ Qxb6 24. Rc7+ Qxc7 25. Rb6+ Qxb6 26. Rc7+ Qxc7 27. Rb6+ Qxb6 28. Bac6+ Qxc6 29. Rb5+ Qxb5 30. Bc6+ Kxc6 31. Qac5+ Qxc5 32. Qd6+ Qxd6 33. Rc5+ Qxc5 34. Rd6+ Qxd6 35. Rc5+ Qxc5 36. Rd6+ Qxd6 37. Rc5+ Qxc5 38. Rd6+ Qxd6 39. Rc5+ Qxc5 40. Rd6+ Qxd6 41. Bgd5+ Qxd5 42. Re6+ Qxe6 43. Bd5+ Kxd5 44. Qhe5+ Qxe5 45. Qd4+ Qxd4 46. Re5+ Qxe5 47. Rd4+ Qxd4 48. Re5+ Qxe5 49. Rd4+ Qxd4 50. Re5+ Qxe5 51. Qe4+ Kxe4 52. Rf4+ Qxf4 53. Re3+ Qxe3 54. Rf4+ Qxf4 55. Re3+ Qxe3 56. Qf3+ Kxf3 57. Rf2+ Qxf2 58. Rg3+ Qxg3 59. Rf2+ Kxf2 60. Be1+ Kxe1

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  • $\begingroup$ I originally thought this, but we're allowed any number of additional pieces (e.g. three white rooks is possible), from my understanding. $\endgroup$
    – Hazel へいぜる
    Commented Oct 4, 2021 at 17:34
  • $\begingroup$ Well, one could be a promoted pawn ;-) But I see your point. $\endgroup$
    – loopy walt
    Commented Oct 4, 2021 at 17:37
  • $\begingroup$ the 60 moves solution. Captures all the checking white pieces $\endgroup$
    – TSLF
    Commented Oct 5, 2021 at 6:01
  • $\begingroup$ @TSLF original version of the question seemed to require that. $\endgroup$
    – loopy walt
    Commented Oct 5, 2021 at 7:55
  • $\begingroup$ @Loopy.. you are right! my intended question. but some cat-in-the-hat edited the OP and I over looked that. Anyway its about "checks & capture" so might as well accept the longer version of 61 moves $\endgroup$
    – TSLF
    Commented Oct 5, 2021 at 16:11

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