In lightning chess matches (matches with time controls of 3 minutes or less on each side), some players play with the rule of "king sniping" - that is, to save time, if the opponent played a move that left his king in check, the other player can simply capture it (thereby winning the game) rather than forcing the opponent to retract his move.

Combined with the rule that the king cannot castle through check (cannot move two spaces if the space between the origin and destination is attacked by an opposing piece), the problem arises of what the appropriate way is to capture the king if this actually happens in a lightning match, as the king is not in a position of check either before or after the opponent's turn. Simply taking the king away might confuse the player because the other piece will have made a technically illegal move, but moving to the square that the king castled through (which amounts to a sort of "en passant" capture, capturing a piece/pawn that moved two squares in a special case as if it had only moved one square) captures the rook instead of the king.

Is there any convention for this?

  • 4
    Or, if you're a ninja, flick the piece they're casting through at the perfect instant to knock the king out of your opponent's hand as it's passing through the covered square. Commented Apr 7, 2014 at 16:37
  • 1
    Note that when playing in an official (FIDE rules) tournament, capturing the king is itself an illegal move. If you try to claim that way and your opponent points it out, you lose. So this is a bad habit to have. Commented Jan 8, 2016 at 22:41

3 Answers 3


When the king castled through check, your opponent made an illegal move. Call it, and you win.

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    en.wikipedia.org/wiki/Fast_chess - "A common rule used in fast chess tournaments is that if a player makes an illegal move, the player's opponent may point it out and claim a win."
    – Tom77
    Commented Jul 29, 2013 at 9:11

I'd say the en passant method is the way to go. There's no conventions for this that I know of.

  • Probably because it happens so rarely, I bet.
    – Joe Z.
    Commented Mar 6, 2013 at 2:14

In blitz, you can take the opposing king (whereas in normal chess, it's illegal to move such that you're in check). Not all blitz is this way: online chess typically just retains the rule that leaving yourself in check is illegal, and this is fine since the computer enforces the rule. In real life blitz, because of the fast pace, the usual convention is that you lose if you leave your king in check. This is to stop people from wasting your time by moving into check, hitting the clock, letting YOUR time run, then taking the move back afterward... it's hard to restore the time you lost.

Normally you just capture the king outright and claim victory in over-the-board blitz. But as you note, you can't do this in a clear fashion when your opponent castles through an attacked square. There are similar illegal moves that could occur: castling with a rook that has already moved, or with a king that's already moved, or simply making an outright illegal move.

The convention I have always used is that illegal moves must be retracted. If the king is OUTRIGHT left in check, you may capture it and declare a win. But simply moving through an attacked square would not qualify, and you would simply hold down your clock button (to stop your opponent from starting your clock) and say, "Illegal castling... please retract the move".

You would not be entitled to capture his king.

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