Originally posted by JusuhWith 'retros' (such as this) it is up to the solver to find out under what conditions a position may or may not be legal.
i dont think so
Do you have any particular reason to believe that the position is illegal?
It seems like a boringly normal position to me.
Let me try. White can still castle. black not.
Key possible events:
- black knight(s) capture(s) both white bishops on c1 and f1
- white knight captures black bishop on f8
- black h-rook comes out (via h6 or f6) and is captured on b3 by a-pawn
- white's a-rook comes out and is captured at b6 by a-pawn
- white queen comes out via a-file and is captured by black's f-pawn on g3 (f4xQg3), and white captures the pawn back hxg3
- black a-rook comes out and goes to h8
- knights and remaining black pawns go to their final position
note: after white rook comes out, the role of white rook and queen can be reversed (queen to be captured on b6; rook to be captured on g3)
number and parity of moves not important, because enough temporization moves available
OK I'll have a go too (I disagree with previous poster!)
OVERVIEW
Captured pieces
White:
Rook
Bishop (W) - can't have moved
Bishop (B) - can't have moved
Queen
Black:
Rook
Bishop (B) - can't have moved
Pawn
White has lost 4 pieces
Black has lost 3 pieces (inc 1 pawn)
2 of white's pawns have captured
At least 1 of black's pawns have captured
None of the bishops have been captured by pawns
Hence, white's pawns MUST have captured a Rook and a Pawn.
Case Pawn on B3
---------------
It can't have taken a pawn on b3, as there are 2 pawns on the b file, one on the c-file, and not enough pieces have been captured for a pawn to have come from the f-file (the 2 bishops can't have moved).
Hence, the only piece it can have captured is the black rook from a8 (not h8, otherwise black would be unable to castle). In order for the rook to have moved, the pawn on a7 must have already captured a piece. Since neither of white's bishops can have moved, it must have captured a rook or the queen. Neither the a-file rook nor the queen can have moved off the a-file, as the pawn wall in front of them would have been complete, UNLESS both bishops had been captured, and the king had moved away from e1 to allow the Queen and rook egress, and then the king returned to e1. Hence, white CANNOT castle.
Case Pawn on G3
---------------
We've already asserted that the pawn on a3 must have captured a rook, hence the pawn on g3 must have captured a black pawn. The pawn must have originally been on f7, so this (Black) pawn must also have made (at least) one capture to arrive at g3. This is consistent with the position, as both the black pawn now on b6 and the black pawn originally on f7 have captured a piece each (white's queen and a rook).
The knights on both sides can be responsible for capturing the respective bishops, so all captured pieces are accounted for.
Black can castle, as we could have arrived at the postion with neither the black king, nor the rook on h8 having moved. (HOWEVER, it is possible that the rook on h8 came from a8. If so, black cannot castle either.)
My answer:
The position is legal.
White CANNOT castle - his king must have moved for the position to be legal.
Black MAY be able to castle - unable to state definitely whether king or remaining rook have moved (they certainly haven't been FORCED to move). Within the spirit of the problem, black CAN castle.
Unless someone else knows different....!
🙂
Originally posted by PawnCurryif the a-rook was captured at b3 (instead of the h-rook as in my solution), then the a-pawn must have captured a white piece on b6 first. That cannot have been the a-rook or queen then, because a2 was still there. But if it was the h-rook, how did it get out? It could get out only after hxg3. But we agree that black's f-pawn capturedd a white piece on g3 before hxg3. Which one ??????????
OK I'll have a go too (I disagree with previous poster!)
OVERVIEW
Captured pieces
White:
Rook
Bishop (W) - can't have moved
Bishop (B) - can't have moved
Queen
Black:
Rook
Bishop (B) - can't have moved
Pawn
White has lost 4 pieces
Black has lost 3 pieces (inc 1 pawn)
2 of white's pawns have captured
At least 1 of black's ...[text shortened]... n the spirit of the problem, black CAN castle.
Unless someone else knows different....!
🙂
Originally posted by PawnCurry23 moves is the best I can do. I still think it can be better. Who can produce this positions in fewer moves?
Just to satisfy my own curiosity, I've played this out on a chess programme, and can arrive at the solution as stated by Mephisto after 34 moves (no doubt this could be bettered).
If anyone's interested I could send/post a list of the moves...?
Originally posted by PawnCurryGosh....you spoil the fun, how long did that take you to write?????
OK I'll have a go too (I disagree with previous poster!)
OVERVIEW
Captured pieces
White:
Rook
Bishop (W) - can't have moved
Bishop (B) - can't have moved
Queen
Black:
Rook
Bishop (B) - can't have moved
Pawn
White has lost 4 pieces
Black has lost 3 pieces (inc 1 pawn)
2 of white's pawns have captured
At least 1 of black's ...[text shortened]... n the spirit of the problem, black CAN castle.
Unless someone else knows different....!
🙂
