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Play the longest game from the starting position such that each move resets the 50 move rule (i.e. is a pawn move or a capture).

As I see it, each pawn quartet on adjacent lines has maximally 4+6+6+6 moves with 4 captures (and the pawns pestering the kings will be a separate problem). After that, 32-2-4 capturable pieces remain. The absolute maximum thus is 114 half moves, but I severely doubt this is reachable.

2 Answers 2

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I have managed 106 single moves (see below).

As OP notes, if 12 pawns promote, capturing the other 4 pawns, then all captures by officers must be on 1st/8th ranks. So that would be 88+26=114.

Can this be improved? It's hard to imagine more than 12 pawns promoting, because it would imply officers being captured in the middle of the board, which they can only reach by capturing pawns themselves in the middle of the board. So we stick with the basic plan, and then there are only two aspects that might in principle be reduced:

  1. Pawns capturing in the promotion move.
  2. Extra pieces on the board in the final position.

Here I have 7+1. (So 5 pawns promote without capture, and there is wQ remaining at game-end.) Theoretically, it might be difficult to go below 4+0, as we need to clear squares for capture-less promotion on each side of each king.

Anyway, here it is...

[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

1. a3 g6 2. a4 g5 3. a5 g4 4. a6 g3 5. hxg3 bxa6 6. g4 a5 7. g5 a4 8. g6 a3 9. g7 a2 10. b3 h6 11. b4 h5 12. b5 h4 13. b6 h3 14.b7 h2 15. g3 a6 16. g4 a5 17. g5 a4 18. g6 a3 19. e3 c6 20. e4 c5 21. e5 c4 22. e6 c3 23. dxc3 fxe6 24. c4 e5 25. c5 e4 26. c6 e3 27. c7 e2 28. c3 e6 29. c4 e5 30. c5 e4 31. c6 e3 32. f3 d6 33. f4 d5 34. f5 d4 35. f6 d3 36. cxb8=R exf1=R+ 37. Kxf1 hxg1=B 38. Rxc8 e2+ 39. Kxg1 e1=B 40. Rxa8 d2 41. c7 axb1=R 42. b8=R Rxa1 43. c8=B Rxc1 44. Qxc1 a2 45. gxf8=N d1=R 46. g7 a1=R 47. gxh8=N Qxc8 48. Qxa1 Qxb8 49. f7+ Kxf8 50. Qxd1 Qxa8 51. fxg8=N Qxh1+ 52. Kxh1 Kxg8 53. Qxe1 Kxh8
2
4

An excellent question which I've no idea of the answer to. To illustrate the difficulties, however, here's a very cursory attempt which only manages to get to 81 half moves.

[FEN ""]

1. d3 h6 2. Bxh6 g6 3. Bxf8 e6 4. e3 c6 5. d4 a6 6. Bxa6 b6 7. Bxc8 d6 8. c3 f6 9. b3 b5 10. e4 c5 11. f3 d5 12. g3 e5 13. f4 f5 14. g4 g5 15. c4 exd4 16. a3 d3 17. a4 d4 18. a5 fxg4 19. a6 g3 20. a7 Rxa7 21. b4 Rxa1 22. e5 g2 23. f5 g4 24. f6 g3 25. h3 d2+ 26. Kxd2 gxh1=R 27. f7+ Kxf7 28. Be6+ Kxf8 29. Bxg8 bxc4 30. b5 Rxb1 31. b6 d3 32. Bxc4 g2 33. Bxd3 c4 34. h4 Rxg1 35. Qxg1 Rxb6 36. Qxb6 cxd3 37. h5 g1=Q 38. h6 Rxh6 39. Qxb8 Qxb8 40. e6 Rxe6 41. Kxd3

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