I was playing chess with an opponent. He had his queen in front of his king. I attacked the queen and he moved her, exposing his king directly to my rook. It was my turn to move, not his. We couldn't decide if this was a checkmate. We know that moving one's king into check is illegal. What happens however, if one removes a piece in front of his/her King and exposes him to checkmate unintentionally, as in this instance? If it's illegal to do this, but the player makes this move anyway, is he required to take back the move and move differently, or does the game automatically end? Thanks in advance.

  • 2
    Thanks so much for your answer! Much appreciated.
    – Clement
    Commented Feb 23, 2020 at 19:54

1 Answer 1


It was illegal to move the queen here (and any piece in general) if that move put the king in check from another of the opponents pieces.

If the player tried to move the queen here they have to put it back and make a legal move.

Note that in some nonstandard variation most usually of the blitz speed type the special rules allow you to take the king and win if they make that illegal move.

Some other variations may allow claiming a win if an illegal move is made. I have played blindfold games where that illegal move was a loss by the special rules for that variation of chess.

  • 2
    Thanks a lot. I used to play at a chess club where we had a rule that an illegal move led to an instant win, which is why we got confused, as my opponent had never heard of this. Your answer pretty much resolved our issue.
    – Clement
    Commented Feb 23, 2020 at 19:53
  • 3
    Note that the opponent would be required to revert the move with the queen, but would still be required to move the queen if there were any legal moves for that piece, even moving some other piece would have been preferable.
    – supercat
    Commented Feb 24, 2020 at 6:40

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