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"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.
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Originally posted by tvochessCorrection: captures, pawn moves and castling are the only irreversible chess moves. In theory, therefore, castling should also be mentioned in the 50 move rule; but who potters about for 50 moves when he hasn't castled yet?
Captures and pawn moves are the only irreversible chess moves. A draw can be claimed after 50 half-moves without capture or pawn moves.
Oh, and another correction: that's 50 full moves, not 50 half-moves. FIDE rule 5.2e.
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Originally posted by Shallow BlueMy bad, it's 100 half-moves indeed.
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.
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!
