24 Mar '08 21:02>
White moves and forces a draw
Originally posted by Mephisto2Wow, that really looks unexpected. All I can think of is 1. c3.
White moves and forces a draw
[fen]nB3RbN/1kppppq1/1p4p1/1P3p2/Bp3P1n/4PrbP/2PP1rP1/R3K3 w[/fen]
Originally posted by heinzkat(also notice the Knights on a8 and h8, and the White Rook on f8, and probably in the same way there must have been something strange going on for Black's Rooks on f2 and f3, and the Bishop on g3.)
I suppose it has something to do with those strangely placed Bishops on b8 and g8 - but I cannot deduce that, for example, there have been no pawn moves or captures in the last 100 half moves.
The pawn structure has something 'retrogradic' in it, though...
Originally posted by Mephisto21. Ba7 and White claims a draw because of the 50-move draw rule.
White moves and forces a draw
[fen]nB3RbN/1kppppq1/1p4p1/1P3p2/Bp3P1n/4PrbP/2PP1rP1/R3K3 w[/fen]
Originally posted by heinzkatMaybe SwissGambit can astound us with retrogradic proof that this position has been reached with no pawn moves or captures during the previous 50 moves.
1. Ba7 and White claims a draw because of the 50-move draw rule.
There is no reasoning behind this particular move and no valid reason for the claim though.
Originally posted by Mephisto2My guess:
White moves and forces a draw
[fen]nB3RbN/1kppppq1/1p4p1/1P3p2/Bp3P1n/4PrbP/2PP1rP1/R3K3 w[/fen]
Originally posted by David113You are on a good track. And yes, if castling can't be proved to be illegal, then it is a possible move. The question is wether castling vs. another white move makes a difference in the number of moves since the last capture/pawn move.
My guess:
White plays O-O-O, and then shows that the fact that he was able to castle implies that the last 50 moves were without captures/pawn moves.
Second thought: this is not very logical - why can't white play any other non-capture, non-pawn move? why does white have to actually castle, since castling is already assumed legal unless proved otherwi ...[text shortened]... astling can't be proved illegal) to prove that 50 moves were made without captures/pawn moves?
Originally posted by Mephisto2This doesn't answer my question - why must white actually castle? Why can't white play any non-capture, non-pawn move, and then argue "in my last move I could have castled, and so..." ?
You are on a good track. And yes, if castling can't be proved to be illegal, then it is a possible move. The question is wether castling vs. another white move makes a difference in the number of moves since the last capture/pawn move.
Originally posted by Mephisto2As other posters have suspected, this one involves both castling and the 50-move rule.
White moves and forces a draw
[fen]nB3RbN/1kppppq1/1p4p1/1P3p2/Bp3P1n/4PrbP/2PP1rP1/R3K3 w[/fen]
Originally posted by David113White has to castle, not because he needs to prove he can castle, but because he needs to prove the 50-move rule applies!
This doesn't answer my question - why must white actually castle? Why can't white play any non-capture, non-pawn move, and then argue "in my last move I could have castled, and so..." ?
My point is, that everything that white can prove by castling, white can also prove without actually castling, because the proof follows from the ability to castle - not ...[text shortened]... ever moved; but according to the chess problem conventions, white never needs to prove that.