10

If one player (Black) gives another player (White) odds of x moves, stipulating that White must not move any man beyond his fourth rank until Black has made one move, what's the smallest value for "x" that would force checkmate by the time it is Black's turn to move? And what would those x moves be?

  • 2
    I seem to remember reading this in a book, and it was somewhere around 16 moves, but I can't be sure, and I don't remember the moves. – Daniel Jun 14 '12 at 17:01
  • I remember reading it in a book too. I guess it was something like the 16-mover or the 14-mover in the answer I just posted. – bof Oct 27 '19 at 0:11
  • You asked for the least number of moves, so why don't you accept my 14 move solution instead of that 15 move solution? – bof Apr 8 at 10:49
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Interesting puzzle.

I came up with this.

[FEN ""]

1. d4 null 2. Qd2 null 3. Qf4 null 4. a4 null 5. Ra3 null 6. Re3 null 7. Nf3 null 8. h4 null 9. Nh2 null 10. Ng4 null 11. Rhh3 null 12. Rhf3 null 13. Nc3 null 14. Ne4 null 15. g3

After Black makes any move, it is a forced checkmate according Houdini. The best move is ’15... f6.’ It allows for mate in 10 moves.

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  • 5
    You wasted a tempo with your queen at the beginning. 1. d4 2. Qd2 3. Qf4 gets her there one move quicker, so really you have it in 15 moves. – ETD Jun 15 '12 at 5:07
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I think something like this is the easiest solution. The set-up takes 16 moves, but then it's only two more moves to checkmate and you don't need a computer to verify it. This is almost the same as Akavall's set-up, except that a knight is posted on c4 instead of g4.

[FEN ""]

1. a4 null 2. d4 null 3. h4 null 4. Nf3 null 5. Na3 null 6. Nd2 null 7. Ne4 null 8. Nc4 null 9. Qd2 null 10. Qf4 null 11. Ra3 null 12. Re3 null 13. Rhh3 null 14. Rhf3 null 15. g3 null 16. Bh3

But you can stop after only 14 moves, and Stockfish announces a forced mate in 7.

[FEN ""]

1. a4 null 2. d4 null 3. h4 null 4. Nf3 null 5. Na3 null 6. Nd2 null 7. Ne4 null 8. Nc4 null 9. Qd2 null 10. Qf4 null 11. Ra3 null 12. Re3 null 13. Rhh3 null 14. Rhf3 d6 (14... d5 15. Qxf7+ Kd7 16. Ne5#) 15. Qxf7+ Kd7 16. Nc5+ dxc5 (16... Kc6 17. Na5+ Kb6 18. Qb3+ Kxa5 19. Qb5#) 17. Ne5+ Kd6 18. dxc5+ Kxc5 19. Qc4+ Kd6 (19... Kb6 20. Qb5#) 20. Qd4+ Ke6 21. Nd3#
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