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The FIDE Laws of Chess state the 50-move rule as follows:

9.3 The game is drawn, upon a correct claim by a player having the move, if:

9.3.1 he/she indicates his/her move, which cannot be changed, by writing it on the paper scoresheet or entering it on the electronic scoresheet and declares to the arbiter his/her intention to make this move which will result in the last 50 moves by each player having been made without the movement of any pawn and without any capture, or

9.3.2 the last 50 moves by each player have been completed without the movement of any pawn and without any capture.

Suppose player A makes a legal move such that:

  • The last 50 consecutive moves have been made by each player without the movement of any pawn and without any capture
  • Player A's move puts player B in checkmate

Can player B invoke 9.3.2 to avoid the loss by checkmate?

EDIT TO ANSWER A QUESTION IN THE COMMENTS

Question: Is it Player A's 50th or 51st move that puts B in checkmate?

It is the 100th half-move (made by player A) that puts player B in checkmate. So in my example, player A makes the even-numbered half-moves (e.g., 100) and player B makes the odd-numbered half-moves. In turn, this means that player B had the first (odd) half-move. So, the move sequence after the last pawn move or capture went:

1. B A 2. B A ... 50. B A#.

Therefore, it is player A's 50th move that checkmates player B.

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  • Could you please clarify something? Is it Player A's 50th or 51st move that puts B in checkmate? The arbiters/TD's here may overrule me, but that would seem important.
    – GreenMatt
    Commented Jul 13, 2023 at 14:01
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    Incidentally, there was once a dispute about this in some game, I think KQN vs KRR where the first player won by checkmate exactly how you described. After that, the rules were clarified (I have been told at least) to make it more clear that checkmate takes precedence over the 50 moves rule.
    – koedem
    Commented Jul 14, 2023 at 8:15

2 Answers 2

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Can player B invoke 9.3.2 to avoid the loss by checkmate?

No.

A player can only invoke the 50 move rule if the game is still being played. Checkmate ends the game. Once the checkmate is on the board the game is over, player A has won, player B has lost. Absent proven cheating, the result stands.

According to the FIDE Laws of Chess:

5.1.1 The game is won by the player who has checkmated his/her opponent’s king. This immediately ends the game, provided that the move producing the checkmate position was in accordance with Article 3 and Articles 4.2 – 4.7.

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    For what it's worth, rule 9.6.2 explicitly says the same about 75 move draw rule (where the game is drawn even if neither player claims it): "If the last move resulted in checkmate, that shall take precedence."
    – JiK
    Commented Jul 13, 2023 at 9:58
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    Yes, the fact FIDE states checkmate takes precedence in the 75-move rule but omits such a statement for the 50-move rule was, in part, what prompted the question.
    – Dave
    Commented Jul 14, 2023 at 0:09
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I’ve grappled with this point before, trying to understand how the FIDE Laws (which are the basis of chess problems) should work.

Essentially the Laws might have been split cleanly into rules of play and tournament guidelines. The rules would basically say that 50 moves without capture, pawn move or checkmate allow a draw claim. The tournament guideline would engage the paraphernalia of scoresheet, clock and arbiters. But that split is not made, so it’s a bit of a mess.

As other answers have said, the mated person cannot claim the draw, because it’s too late. But the other side of the coin is whether the mater might, in principle, interrupt their own mating move in order to claim the draw instead. That would not be rational, but it does appear to be legal.

Maybe for subtle tournament reasons it would be advantageous for a player to draw rather than win. I wonder what an arbiter would make of this?

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    This is an interesting point. It does indeed sound legal to claim a draw. I hope an arbiter will chime in!
    – Dave
    Commented Jul 16, 2023 at 23:52

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