Originally posted by BigDoggProblem Only one of those moves is legal. Which one?
I am not done with the puzzle yet, but it has to be Qxc6#. Black is on the move, otherwise the position would be illegal. White's last moves were 1.a6-a7 2.a7-a8R 3.Ra3 4.Rf3 (or another rank 3 move) 5.Rf1 6.Rh1
Black has exactly 5 moves during that episode (which excludes that he would have made the last move) with the h-pawn (4 captures and one advance move) to arrive at d2. No other moves available before the white pawn is on a6. Before that, black captured on b6 with the a-pawn.
It still takes some work to find out how this position arrived, especially how whitte's king arrived there without going into check. White didn't capture anything, so the c-pawn just stepped forward. I suspect the black c-pawn went via d6 (capturing the bishop?) to c5 (capturing a rook). The maneuvre with the black rook (and the white one on the c-file) is still not clear.
Originally posted by Mephisto2 I am not done with the puzzle yet, but it has to be Qxc6#. Black is on the move, otherwise the position would be illegal. White's last moves were 1.a6-a7 2.a7-a8R 3.Ra3 4.Rf3 (or another rank 3 move) 5.Rf1 6.Rh1
Black has exactly 5 moves during that episode (which excludes that he would have made the last move) with the h-pawn (4 captures and one advance ...[text shortened]... re with the black rook (and the white one on the c-file) is still not clear.
Comments anyone?
I believe that starting at the diagram and retracting moves one by one is the best way to solve these. It takes a little time to get used to it, but it avoids the trial-and-error element of trying to create a past position and play forward to the diagram. I will use retro notation (a '-' sign in front of the move numbers to show retractions.
If we follow Mephisto2's line in this manner, we get:
-1.Rf1-h1 e3xPd2 (when a piece is uncaptured, the type of piece must be listed)
-2.Rf3-f1 e4-e3
-3.Ra3-f3 f5xPe4
-4.Ra8-a3 g6xPf5
-5.a7-a8R h7xPg6
-6.a6-a7 a7xBb6
-7.Ba5-b6 b6xRc5
-8.Rc3-c5
...and we have a problem. Black is completely stuck and can't retract any moves! This is known as retro-stalemate. A position in this state is obviously illegal. Too bad...if white only had one more move, he could withdraw the Rook on c6 and give Black some breathing room.
Originally posted by BigDoggProblem I believe that starting at the diagram and retracting moves one by one is the best way to solve these. It takes a little time to get used to it, but it avoids the trial-and-error element of trying to create a past position and play forward to the diagram. I will use retro notation (a '-' sign in front of the move numbers to show retractions.
If w ...[text shortened]... ite only had one more move, he could withdraw the Rook on c6 and give Black some breathing room.
The rook on h1 needed 4 moves to get there from a8. If instead, white's pawn promoted to a queen, the queen could get back to d1 in 3 moves. The original queen must have played the role of the original rook and had to be captured by a pawn. How about:
Originally posted by Mephisto2 The rook on h1 needed 4 moves to get there from a8. If instead, white's pawn promoted to a queen, the queen could get back to d1 in 3 moves. The original queen must have played the role of the original rook and had to be captured by a pawn. How about:
Right. Unpromoting the white Queen saves a move on the other line. This is the retraction sequence that proves that Black must have the move in the diagram. Good work!
Mate in 1
23 Sep '05 17:32
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