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An arbiter is trying to figure out what happened on the above adjorned game. He only knew that black made 15 moves and there can be more than one line of moves for this. Can you replay at least one game history for the arbiter?

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    $\begingroup$ Looks like white pieces moved to extreme right. $\endgroup$ – Techidiot Nov 14 '16 at 17:29
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    $\begingroup$ yes, we are looking on a side as the arbiter $\endgroup$ – TSLF Nov 14 '16 at 17:35
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    $\begingroup$ You sure it is possible in 16 white moves? $\endgroup$ – Sid Nov 14 '16 at 17:59
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    $\begingroup$ @Dr Xorile- I played it on Chess Titan (MS 7 built in Games). It is a 3D rotatable program. $\endgroup$ – TSLF Nov 14 '16 at 18:37
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    $\begingroup$ @Techidiot That's not possible, the lower-right square is always white. We must be looking at it from the side. $\endgroup$ – BlueRaja - Danny Pflughoeft Nov 15 '16 at 4:21

Here's a solution:

1. Nf3 e5
2. Nxe5 Ne7
3. Nxf7 Ng6
4. Nxd8 Nf4
5. Nxb7 a5
6. Nxa5 c6
7. Nxc6 Nh3
8. Nxb8 Bb7
9. Nxd7 Ra5
10. Nxf8 g6
11. Nxh7 Rf8
12. Nxf8 Bc6
13. Nxg6 Re5
14. Nxe5 Bf3
15. Nxf3 Ng1
16. Nxg1

Here's some of the logic for finding it:

Firstly, the white knight must be taking a piece every turn apart from the first one. That means it has to take a piece on it's home square. To do that, you have to set up a path so that the black pieces can move into the last spot. Especially, you need a knight to jump into the white knight's home square (without checking the king). No checks can occur in general (one exception is possible, if the black knight checks and then gets captured).

Here's a link to the moves: Clear the board!

And here's a gif (thanks to chess.com's gif maker):

lone king solution gif

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    $\begingroup$ Well, you beat me to it. I had just found that. My "Aha" moment. :-) $\endgroup$ – Sid Nov 14 '16 at 18:24
  • $\begingroup$ Pretty close. I thought it wouldn't take too long! I up-voted the other solution. Clearly simultaneous work... I was wondering if the puzzle could be tweaked to state that someone heard one of the players say "Check!" $\endgroup$ – Dr Xorile Nov 14 '16 at 18:26
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    $\begingroup$ I have found a solution where one of the players is heard to say "check!". The solution is here $\endgroup$ – Dr Xorile Nov 14 '16 at 18:39
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    $\begingroup$ The demo really makes this answer great $\endgroup$ – Code Whisperer Nov 15 '16 at 14:13
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    $\begingroup$ I love that stockfish quietly works out that it's mate in 7 from the final position... $\endgroup$ – Dr Xorile Jan 5 '17 at 20:13

I found the following:

1. Nc3 d5 2. Nxd5 Nf6 3. Nxe7 g6 4. Nxg6 Ne4 5. Nxh8 Nc3 6. Nxf7 h6 7. Nxh6 Bf5 8. Nxf5 Qe7 9. Nxe7 c6 10. Nxc6 b6 11. Nxa7 Nc6 12. Nxc6 Ra7 13. Nxa7 b5 14. Nxb5 Ba3 15. Nxa3 Nb1 16. Nxb1
Final Position

The key is that

A White Knight must move such that every turn other than the first results in a capture, and no move results in a check. This requires a Black Knight on the White Knight's starting square, and Black pieces making a chain back from black's home ranks. I used a Pawn and Bishop.

  • $\begingroup$ "...and no move results in a check." Why? The king can step out of check and step back to its original position later. $\endgroup$ – Brian Nov 15 '16 at 17:30
  • $\begingroup$ @Brian If the king moves then it needs to capture on that move, and it needs to capture on its returning move. $\endgroup$ – trichoplax Nov 15 '16 at 19:15
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    $\begingroup$ I think the confusion is about which side is checking. The white knight checking the black king would be fine, but not black checking white. $\endgroup$ – Set Big O Nov 15 '16 at 19:17
  • $\begingroup$ It seemed initially as if Black spending two wasted moves on the king wouldn't allow for the chain to continue, it may have been proven incorrect since, but it was still part of how I initially attacked the problem $\endgroup$ – Sconibulus Nov 15 '16 at 19:25

1.Nf3 g5 2.Nxg5 b6 3.Nxh7 c6 4.Nxf8 e6 5.Nxd7 Qc7 6.Nxb8 f5 7.Nxc6 f4 8.Nxa7 Nf6

9.Nxc8 Ne4 10.Nxb6 Ng5 11.Nxa8 Nh3 12.Nxc7+ Ke7 13.Nxe6 Ng1 14.Nxf4 Rh3 15.Nxh3

Ke8 16.Nxg1

This one has the checked king. It is about the linking of knight captures.

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    $\begingroup$ Here's a link to your game. I had a different solution (see comments in my solution) where black gets the check. Possibly, we can get more than one check then... $\endgroup$ – Dr Xorile Nov 14 '16 at 18:54
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    $\begingroup$ I still read lichess as female lich. $\endgroup$ – Joshua Nov 14 '16 at 21:13

As the question as-is has already been answered correctly, with examples of how check on either side can be achieved. I therefore decided to present my thoughts on why it appears unlikely that check on both sides can be achieved.

The main reasoning depends on the counting of moves required by black:

  • 1 start bridge move (e5 or g5)
  • 8 knight moves (to g1 and f3)
  • 2 king moves
  • 1 end bridge move (to a square that attacks f3)

  • 1 move to 'deal with' a8

  • 1 move to 'deal with' h8 (unless Rh5 can be the end bridge)
  • 1 move to deal with a7 (not h7 because it can be solved with a bridge move)

Which basically means you have 1 move left to facilitate the continuous capturing of the Knight AND the check.

I therefore doubt whether it is possible to get this position in 16 moves with check on both sides. Here is the closest I have come so far, running just a half move short, perhaps it will inspire someone.

1. Nf3 g5 2. Nxg5 b6 3. Nxh7 Nc6 4. Nxf8 Nd4 5. Nxd7 c6 6. Nxb6 Nf6 7. Nxc8
Nh5 8. Nxa7 Kf8 9. Nxc6 Ra6 10. Nxd8 Rg6 11. Nxf7 e5 12. Nxh8 Nf4 13. Nxg6+
Ke8 14. Nxe5 Nf3+ 15. Nxf3 Nh3

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