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The purpose of this puzzle is to find the minimum number of moves to checkmate all the kings.

![enter image description here

RULES

  • You are playing as White and you can make as many moves as you want before Black's turn.
  • During your moves you can take any black piece except kings.
  • During your moves your king can not be in check position.
  • At the end of your turn all the black kings must be check mate : if Black can make one move that ends with one king being safe, you don't win. Note that this one move can't be a king moving to a threatened position.
  • One piece can be used in multiple checkmates (you don't have to take all the king, just to checkmate them)

Examples :

enter image description here
This is a valid ending position because both kings are check mate (A king can not move in a check position to defend another king)

enter image description here
This is not a valid ending position because one of the king is not checkmate

enter image description here
This is a valid ending : a single piece can checkmate 2 kings

I have tried to make this first puzzle easy to introduce the concept. I will make harder similar puzzles later, feel free to create one yourself too...

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  • $\begingroup$ The two valid/not valid examples where only a part of the board is shown are a bit confusing for me: the "not valid" example seems like not a checkmate only because the leftmost king can move up/down into a non-threatened square. However, without seeing more of the board in the "valid" solution, couldn't either king just move vertically out of the threatened area? $\endgroup$
    – Arkku
    Commented Oct 16, 2016 at 12:20
  • $\begingroup$ I'm struggling with your use of the term 'checkmate'. Isn't 'check' when it's threatened, and 'mate' when it cannot make a move to a safe spot? You seem to be using the term 'checkmate' rather then 'check' in your examples. $\endgroup$
    – Tim Couwelier
    Commented Oct 17, 2016 at 10:14

3 Answers 3

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I got a quick answer but not sure how good it is.

1 rook to g6(2 moves), the other rook at a8(1 move)
1 knight to d5(2 moves), the other knight to e5(3 moves)
total 8 moves

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  • $\begingroup$ You are close, but I think your king is in a check position, which is not allowed $\endgroup$
    – Fabich
    Commented Oct 15, 2016 at 22:55
  • $\begingroup$ Thanks for the edit... I knew I would make a silly mistake lol... $\endgroup$
    – stack reader
    Commented Oct 15, 2016 at 23:00
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The answer is indeed

$8$

as stack reader discovered but here is a visual of the moves:


enter image description here

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  • $\begingroup$ I have a more optimal solution $\endgroup$
    – Dr Xorile
    Commented Mar 18, 2017 at 17:06
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I believe it can be done in

7 moves: Rxa8 (1 move); N-b4-d3-e5 (3 moves); Rc3-c6 (2 moves); Bc3 (1 move)

If you want a board to play on, you can use this one on lichess.

Here's the animation:

enter image description here

Edit: sadly it does not work. The rook can be taken by the b7 pawn.

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  • $\begingroup$ This isn't checkmate sadly. The pawn at B7 can take the rook at C6 putting the king furthest left out of check. $\endgroup$
    – Beastly Gerbil
    Commented Mar 18, 2017 at 17:49
  • $\begingroup$ Good point! What a shame $\endgroup$
    – Dr Xorile
    Commented Mar 18, 2017 at 19:00
  • $\begingroup$ Leave it here though, it is still a nice answer. You might want to edit in an explanation of why this doesn't work though $\endgroup$
    – Beastly Gerbil
    Commented Mar 18, 2017 at 19:16

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