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  1. 07 Apr '15 11:47 / 1 edit
    In my ongoing game currently we have played 44 moves. There is also reported 21 "half moves".What is half moves?
  2. 07 Apr '15 15:50
    "half moves" refers to the amount of half moves since last capture or pawn move. It somehow measures the progress in the game. Captures and pawn moves are the only irreversible chess moves. A draw can be claimed after 50 half-moves without capture or pawn moves.

    Each move consists of 2 half moves: one for white and one for black.
  3. 07 Apr '15 16:13 / 1 edit
    Draw can be claimed after 50 moves without a capture or pawn move (100 half-moves).
  4. 07 Apr '15 16:21
    Thank you, now I understand.
  5. 07 Apr '15 18:33
    Originally posted by tvochess
    Captures and pawn moves are the only irreversible chess moves. A draw can be claimed after 50 half-moves without capture or pawn moves.
    Correction: captures, pawn moves and castling
    or moving a previously unmoved king or rook
    are the only irreversible chess moves. In theory, therefore, castling
    et al.
    should also be mentioned in the 50 move rule; but who potters about for 50 moves when he hasn't castled yet?

    Oh, and another correction: that's 50 full moves, not 50 half-moves. FIDE rule 5.2e.
  6. 07 Apr '15 20:21
    Originally posted by Shallow Blue
    Correction: captures, pawn moves and castling [hidden]or moving a previously unmoved king or rook[/hidden] are the only irreversible chess moves. In theory, therefore, castling [hidden]et al.[/hidden] should also be mentioned in the 50 move rule; but who potters about for 50 moves when he hasn't castled yet?

    Oh, and another correction: that's 50 full moves, not 50 half-moves. FIDE rule 5.2e.
    My bad, it's 100 half-moves indeed.

    By the way, castling can be reversed as much as any other move. See this constructed game for example.



    So castling can be reversed. But you are right as well since castling availability has been destroyed. So the position after Black's 4th and 9th moves is not technically the same. Although you could do some manual castling again. This is mainly a semantical discussion anyway, because reversing moves like doesn't make any sense.

    Afterthought: there must be situations in which castling cannot be undone.



    So Shallowblue, you were absolutely right in saying that castling is irreversible!
  7. 07 Apr '15 21:29 / 1 edit
    You can Uncastle and Castle again by accident.

    W. Heidenfeld - N. Kerins, Dublin, 1973.