Deductive Puzzle #46

Three facts of this game are known: Neither White's king's Knight of Queen's Knight ventured beyond the 6th row; The Black Royalty have never moved nor been under attack; The Black king's knight has moved only once.

Knowing this, deduce whether the White Queen on the board is the original or a promoted pawn.

Knight's haven't travelled beyond the sixth row being inclusive (i.e. they could have been on 6th, but not 7 or 8)?  I suppose it must be as the puzzle is far too easy otherwise.

Inclusive.

Well, white's light-squared bishop was taken on f1 by a knight.

A white piece was captured on c6. This can't have been a bishop or knight (would've attacked the black queen), so it must have been the a-pawn, a rook, the original queen, or a promoted piece.

Another white piece was captured on d6. This ALSO could not have been a knight, as it would have attacked the king.

Based on these two observations, white must have had a rook captured on one of those two squares, and the other piece captured was either the original dark-squared bishop, the original queen, or a promoted piece (which would have, necessarily, been a bishop or queen).

A black piece was captured on g3. Must have been either the queen's knight or the dark-squared bishop.

In order for the white a-pawn to promote it must have captured onto the b-file and then captured again to get back to the a-file, and it must have then promoted on a8 while the black rook was on b8 or c8. This means white must have promoted to queen. This accounts for the other two of black's pieces which were captured.

dxc6 had to have been played before the white a-pawn promoted, as this is the only way for black's light-squared-bishop to get itself over to the b-file to get captured. exd6 must have been played before dxc6 or before the promotion, because otherwise the white piece sacrificing itself on d6 would have attacked the black queen, as there isn't a piece available to block the file otherwise (the only options are queen's knight, bishop, and pawn; both pieces must be captured before promotion, unless exd6 has already been played in which case the dark-squared bishop can get itself captured instead).

Therefore the original queen sacced itself on c6 or d6, so the queen currently on d1 is a promoted pawn.

It's not the easiest explanation to follow, but I hope you understand it.

Original--the only pawn that could have been promoted is the rook's pawn on A2.  Since there are no breaks in the black pawn wall on the queen side, there is no promoting square it could have reached.

WanderingWinder, I'm with you on the Knights, but why couldn't a Bishop have been captured on c6?  The pawn that captured it would have blocked the attack on the Queen....

I'll take a closer look when I get home.  I've not had time to thoroughly read your post as I'm at work and it could easily be that I've misunderstood.

Hard one.

The first thing that strikes me is that isn't this position impossible? Otherwise, how could the white light-squared bishop have been captured (as it could never have left it's own square)? It couldn't have been the black king or queen because neither piece has moved. It couldn't have been a rook, because the rooks couldn't get out onto the board. None of the minor pieces could have captured it, and black still has all 8 of his pawns on the board (so it couldn't have been a pawn). So what's going on here?

Immediately we can see that the two captures on c6 and d6 were not the captures of Knights, and since it’s clear that White’s missing bishop was captured on f1 it must have been the missing rook, and either the missing pawn or a piece that it subsequently replaced after promoting.

Black is missing three pieces, once of which was captured on g3 so it is possible that the c6 capture was the missing a-pawn as two captures would be sufficient for it to have made it to the c-file (leaving the d6 capture to have been the rook).

It’s also possible that the pawn promoted by capturing first to the b-file, and then back onto a7 to promote on a8 and that the c6 and d6 captures are the original Queen and Rook.

So which case occurred?  We can see that the capture on g3 wasn’t the light squared Bishop as it is a dark square so this means that one of the two captures made by White’s missing pawn must have been the light squared Bishop, but in the case where the Queen is the original how did the light squared Bishop get out to be captured by the pawn before the pawn was captured on c6?  It’s not possible for this to have occurred, so the other scenario must be what happened with the White Queen or Rook being captured on c6 and the pawn promoting on a8 therefore the Queen is not the original, but is in fact the promoted a-pawn.

It appears that the information about how far the Knights vendured is not required to solve this one.

WanderingWinder, I just read your solution and with the exception of the reasoning for why White's missing Bishop wasn't one of the two obvious Black captures you got it first.

It occurs to me that I haven't addressed why the pawn couldn't have promoted to a peice other than a Queen in my solution.  The answers should be relatively obvious, but it needs to be stated in order for the solution to be complete:

• It can't have been a rook because the only escape route to either get to d6 or h1 would be via d8 requiring both the Black Queen and King to move.
• It can't have been a the dark sqaured Bishop becase a8 is a light coloured square.
• It can't have been a light squared Bishop because it could neither have escaped from a8 nor could it have been captured on d6 which is a dark square.
• And finally, it can't have been a Knight because the requiremnet that it was subsequently captured on d6 means, like the original Knights, that it would have put the Black King in check which we know did not happen.

Bishops couldn't have been captured on d6 or c6 because a) the light-squared bishop couldn't have escaped b) the dark-squared bishop is still on the board and c) a promoted bishop couldn't have escaped from its promotion - there aren't enough black pieces missing for the pawn to have promoted on b8.

I see -- meaning a promoted Bishop because of the obvious capture of the original light-squared Bishop on f1.  I misunderstood.

I think the only thing missing, then, was the explanation as to why it had to have been a Queen that was captured initially and that the pawn promoted to as opposed to one of the other pieces that remained on the board or that could have subsequently been captured on d6.  I also had to add as an addendum to my solution.

Does royalty include the rooks? (specfically the a8 rook)

If not, the queen is original since the a-pawn needs to take the three missing black minor pieces to fit through the black squares b6 -> a7 -> b8. One bishop must be white so three pieces were not available.

If royalty does include rooks the queen can still be original but may not be...

*gives blank stare / walks away* ^_^

I am 99.999% sure I am not thinking enought but

I think the White Q is original because: if the black royalty have never moved nor been under attack, then no pawn would have been able to get to the 8th rank without attacking the black K or Q.