Place the white King on the board...
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Thanks, rooperi.
a is trivial: +Ka4#
b is not so trivial: +Kc5, 1. axb6ep#
Put Kc5. White has 13 pieces; the missing three pieces go to exfxgxh4, so b and c pawns didn't capture. The only possible pawn retraction is thus b7-b5, which allows e.p. capture. Can Black moved some piece before?
Rooks and bishops are locked. Ka3-a2 is impossible; the knight on b1 has no last move. Kb3-a2 is similarly impossible due to Qc2 having no last move. So the king didn't move last. Queen cannot come from a3 or b4; it checked White's king and then lifts the check, illegal. If the queen came from b3, Black is checked by the queen and there's no legal retraction for the queen. Thus no Black piece moved last, and thus Black's last move was b7-b5. Forward play 1. axb6ep#.
chaotic_iak wrote:
a is trivial: +Ka4#
.......why is the ep capture not possible here?
rooperi wrote:
chaotic_iak wrote:
a is trivial: +Ka4#
.......why is the ep capture not possible here?
Last move may have been -1...b6-b5.
Oh, right, I forgot to specify that one. Yes, last move might be -1... b6-b5, so White cannot capture en passant and it's a mate.
I've just found another 'Place the White's king on the board', which is pretty much more simpler than BigDogg's original problem, but interesting nevertheless.
Problem extrated from The Chess Mysteries of the Arabian Knights, by Raymond Smullyan.
The_Worstiest wrote:
I've just found another 'Place the White's king on the board', which is pretty much more simpler than BigDogg's original problem, but interesting nevertheless.
Problem extrated from The Chess Mysteries of the Arabian Knights, by Raymond Smullyan. Pieces:WBa4, BKd1, BRb5, BBd5(I've tried to post a diagram with such position, but it didn't worked. Not sure where i went wrong there).
Heh, I can only hope to someday make a problem as awesome as that one.
chaotic_iak wrote:
b) is not so trivial: +Kc5, 1. axb6ep#
Put Kc5. White has 13 pieces; the missing three pieces go to exfxgxh4, so b and c pawns didn't capture. The only possible pawn retraction is thus b7-b5, which allows e.p. capture. Can Black moved some piece before?
How can you be sure that Black's pawn wasn't already on b6 in that case, making the axb6# e.p an illegal move? I don't got it.
The_Worstiest wrote:
chaotic_iak wrote:
b) is not so trivial: +Kc5, 1. axb6ep#
Put Kc5. White has 13 pieces; the missing three pieces go to exfxgxh4, so b and c pawns didn't capture. The only possible pawn retraction is thus b7-b5, which allows e.p. capture. Can Black moved some piece before?
How can you be sure that Black's pawn wasn't already on b6 in that case, making the axb6# e.p an illegal move? I don't got it.
If the white king was on c5, black's pawn couldn't have come from b6 where it would be checking white's king. It must have come from b7.
Placing the white king on the fifth rank next to the pawn to eliminate the single pawn step is the oldest and simplest trick in composing these e.p. puzzles. In some cases it's a dead giveaway of an e.p. puzzle.
Remellion wrote:
The_Worstiest wrote:
chaotic_iak wrote:
b) is not so trivial: +Kc5, 1. axb6ep#
Put Kc5. White has 13 pieces; the missing three pieces go to exfxgxh4, so b and c pawns didn't capture. The only possible pawn retraction is thus b7-b5, which allows e.p. capture. Can Black moved some piece before?
How can you be sure that Black's pawn wasn't already on b6 in that case, making the axb6# e.p an illegal move? I don't got it.
If the white king was on c5, black's pawn couldn't have come from b6 where it would be checking white's king. It must have come from b7.
Placing the white king on the fifth rank next to the pawn to eliminate the single pawn step is the oldest and simplest trick in composing these e.p. puzzles. In some cases it's a dead giveaway of an e.p. puzzle.
I was for some unknown reason thinking on that b) case with the White's king still out of board, believing that any other square would work, e.g, d6, e5, f8, rather than the only one c5.
Indeed, as you said, Black's b-pawn couldn't be on b6 otherwise White's king would be in check. So, it has been come from b7, and the last moves were 1...b7-b5 2.axb6# e.p. Thanks for the clarification.
These statements are in general very simple(I've been reading some of these tecniques on BigDogg's thread 'Retros for Dummies' lately), but still very possible to forget sometimes.
a) such that white is checkmated.
b) such that white has mate in 1.