19 Mar 08
4 edits
Originally posted by heinzkatIf black played g5 last move how does that stop him from castling now? Black can castle the first move isn't Ke5 its hxg6e.p. because like you said g5 must have been blacks last move.
I suppose you have to prove why 1. ... O-O is not an option for Black - in other words, why g7-g5 must have been Black's last move.
Edits for grammar and I said hxg5 😳
19 Mar 08
Originally posted by heinzkatI believe that in a problem a side cannot castle only if this is stipulated or it can be proven by retrograde analysis that the king or the rook has move..since it wasn't stipulated and it can't be proven that black has moved a king or the rook we can assume that g5 was blacks last move I think...now the problem is how do we prove it was g7-g5 and not g6-g5 😕
But maybe Black cannot castle since his last move was either Ke8 or Rh8 - hxg6 is forbidden then. I suppose there are two solutions - or we are missing something retrogradic.
19 Mar 08
3 edits
Originally posted by SwissGambitI certainly hope that the board isn't upside down (White playing from the top and Black playing from the bottom), preventing Black from castling. If so, that's one dirty trick, and you'd better start running, because the lynch mob isn't far behind. 😉
Not yet....
If that's not the case, then I have no idea. I've looked at this for over 30 minutes, and I can't see anything beyond what the others have already suggested.
Edit - And for the record, if the board is upside down, then the answer is 1.Kd3 (any move, but castling not allowed) 2.Re1#.
Edit 2 - Oops, not sure about that answer. Black's pawn could take the bishop.
Edit 3 - Unless I'm missing something basic, the only thing that makes sense is that we have to somehow prove that Black has just played g7-g5. But I can't see how that can be proved. (I'm not a retrograde kind of guy.)
19 Mar 08
Originally posted by Mad RookIt's funny - all the necessary analysis has already been done, but still nobody has reached the correct conclusion.
I certainly hope that the board isn't upside down (White playing from the top and Black playing from the bottom), preventing Black from castling. If so, that's one dirty trick, and you'd better start running, because the lynch mob isn't far behind. 😉
If that's not the case, then I have no idea. I've looked at this for over 30 minutes, and I can't see an ...[text shortened]... ed g7-g5. But I can't see how that can be proved. (I'm not a retrograde kind of guy.)
The board is not upside down.
There are not two solutions.
19 Mar 08
Originally posted by SwissGambitBy not two solutions, you mean it's not a conditional answer? (If Black just played g7-g5, then White plays this, and if Black just moved his king or rook, then Black plays that.) Are conditional answers allowed in retrograde analysis?
It's funny - all the necessary analysis has already been done, but still nobody has reached the correct conclusion.
The board is not upside down.
There are not two solutions.
19 Mar 08
Originally posted by Mad RookYes, the answer is conditional. But that doesn't make it two solutions. The one thing we can prove is that there is only one move that forces mate in 2. We just don't know for sure what it is.
By not two solutions, you mean it's not a conditional answer? (If Black just played g7-g5, then White plays this, and if Black just moved his king or rook, then Black plays that.) Are conditional answers allowed in retrograde analysis?
Your turn.