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Consider a position where if was player A's turn, they could make a series of moves ("the mating sequence") with forced mate.

However, it is player B's turn, and they can make a series of "delaying moves", which A needs to respond to. (Probably they are spite checks, but perhaps not necessarily). If A could proceed with the forced mate, it doesn't count as a delaying move.

At the end of the sequence of the delaying moves, A can play the exact same mating sequence to win. (The mating sequence doesn't need to be one fixed sequence of moves played regardless of B's moves, as long as the tree of moves is unaffected by the delaying moves.)

Puzzle/Question: What is the longest (finite) sequence of delaying moves?

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  • You might CQL that one for an OTB game by looking for permanent checks of Black, followed by 1-0. (Or colors swapped.)
    – Hauke Reddmann
    Commented Feb 28 at 19:31

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If we rewind this problem back by a move, we have a delay of 100 moves.

[Title "Frederik Willem Nanning, Tijdschrift van den Koninklijken Nederlandschen Schaakbond 1935, Mate in 100"]
[FEN "8/p1p1p3/2p3p1/6Pb/p3P1kr/P1p1PNn1/2P1PKRp/7B b - - 0 1"]
[startflipped ""]

1... Rh3 2. Ke1 Rh4 3. Kd1 Rh3 4. Kc1 Rh4 5. Kb1 Rh3 6. Ka2 Rh4 7. Ka1 Rh3 8. Kb1 Rh4 9. Kc1 Rh3 10. Kd1 Rh4 11. Ke1 Rh3 12. Kf2 a6 13. Ke1 Rh4 14. Kd1 Rh3 15. Kc1 Rh4 16. Kb1 Rh3 17. Ka2 Rh4 18. Ka1 Rh3 19. Kb1 Rh4 20. Kc1 Rh3 21. Kd1 Rh4 22. Ke1 Rh3 23. Kf2 a5 24. Ke1 Rh4 25. Kd1 Rh3 26. Kc1 Rh4 27. Kb1 Rh3 28. Ka2 Rh4 29. Ka1 Rh3 30. Kb1 Rh4 31. Kc1 Rh3 32. Kd1 Rh4 33. Ke1 Rh3 34. Kf2 c5 35. Ke1 Rh4 36. Kd1 Rh3 37. Kc1 Rh4 38. Kb1 Rh3 39. Ka2 Rh4 40. Ka1 Rh3 41. Kb1 Rh4 42. Kc1 Rh3 43. Kd1 Rh4 44. Ke1 Rh3 45. Kf2 c4 46. Ke1 Rh4 47. Kd1 Rh3 48. Kc1 Rh4 49. Kb1 Rh3 50. Ka2 Rh4 51. Ka1 Rh3 52. Kb1 Rh4 53. Kc1 Rh3 54. Kd1 Rh4 55. Ke1 Rh3 56. Kf2 c6 57. Ke1 Rh4 58. Kd1 Rh3 59. Kc1 Rh4 60. Kb1 Rh3 61. Ka2 Rh4 62. Ka1 Rh3 63. Kb1 Rh4 64. Kc1 Rh3 65. Kd1 Rh4 66. Ke1 Rh3 67. Kf2 c5 68. Ke1 Rh4 69. Kd1 Rh3 70. Kc1 Rh4 71. Kb1 Rh3 72. Ka2 Rh4 73. Ka1 Rh3 74. Kb1 Rh4 75. Kc1 Rh3 76. Kd1 Rh4 77. Ke1 Rh3 78. Kf2 e6 79. Ke1 Rh4 80. Kd1 Rh3 81. Kc1 Rh4 82. Kb1 Rh3 83. Ka2 Rh4 84. Ka1 Rh3 85. Kb1 Rh4 86. Kc1 Rh3 87. Kd1 Rh4 88. Ke1 Rh3 89. Kf2 e5 90. Ke1 Rh4 91. Kd1 Rh3 92. Kc1 Rh4 93. Kb1 Rh3 94. Ka2 Rh4 95. Ka1 Rh3 96. Kb1 Rh4 97. Kc1 Rh3 98. Kd1 Rh4 99. Ke1 Rh3 100. Kf2 Rh4 101. Rxg3#
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  • That's a great problem. I wonder whether the OP will allow it even though Black can in fact interfere with the Ra8# by playing Rxb6 on moves 24, 25, or 27 (though White still mates in two by answering Rxb6 with Rh7+).
    – Noam D. Elkies
    Commented Feb 29 at 5:50
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    An epic problem, also regarding that the point of underpromotion is seen only after an age and after Black has jettisoned nearly a complete army for stalemate.
    – Hauke Reddmann
    Commented Feb 29 at 7:43
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    @NoamD.Elkies I have secured a problem that is sound under the conditions. And sorry Hauke, it could not last long as a contender.
    – Rewan Demontay
    Commented Feb 29 at 9:18
  • Yes, this is much better for the stated task (even though as a problem it has minor duals because the wK can traverse the corner triangle in either direction). For the benefit of anybody reading the comments long after the fact, the first few comments concern the Bo Lindgren problem that can be found in the edit history. (@RewanDemontay could have left that answer up and posted a new one with the 100-move delay.)
    – Noam D. Elkies
    Commented Feb 29 at 15:50
  • Just to clarify - your comment about moves 24, 25 and 27 don't apply anymore, right?
    – Steve Bennett
    Commented Mar 1 at 6:19

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