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Nicola Lupinacci (2008-08-01 13:19:52)
ChessPosition (see diagram)
A problem from J. D. Beasley
What was White's first bishop move?
Normajean Yates (2008-08-03 01:46:50)
ok - noted - will try!
Will try - if successful, will post answer after 24 hours. [White's original-f1-B was obviously captured on its own square as it couldn't have moved..]
Normajean Yates (2008-08-04 03:10:23)
not easy - only trivial progress made ..
the trivial part : the black B on board is clearly the promoted original-e-pawn. Hence that pawn must have made exactly 3 or 5 captures in order to promote on the light square b1. That is 3-or-5 out of 6 possible [as the original white-f1-B was captured on its original square].
Running a fever so unable to concentrate and progress beyond that yet. So Nicola please withold the solution for 3-4 days!
If someone else solves it and posts the solution then I say in advance 'well done!'
Normajean Yates (2008-08-04 03:25:03)
after the prev post: - more progress
Now one obvious clue is asking the question: okay black's e-pawn promoted to a bishop on b1: the bishop we now see on g6. Now: how did that black B come out from b1? Obviously via a2. So white's b-pawn moved to b3 *after* the promoted bishop left b2.
It follows that:
First, the black pawn promoted to B on b1. *Then*, after the promoted bishop got out via a2, *then* the white b-pawn moved! So the black pawn made exactly 5 captures to promote. Further, the White B's first move was *after* the black P's promotion to B and then the promoted B getting out via a2.
It should not be too difficult after this ... :) lets see..
Heinz-Georg Lehnhoff (2008-08-04 17:57:20)
Maybe another try ...
I think your plan is not the right one, because you cannot capture the white queen (or the rook of h1) with the black e-pawn on his way to b1. According to your plan the white queen only can go to d1,e1,f1 or g1 before the promotion of the black pawn.
Nicola Lupinacci (2008-08-05 00:02:35)
Heinz-Georg Lehnhoff is right
The pawn made five captures, but if promotion took place before the c1 bishop moved there would only have been four pieces available for capture, namely the a-rook, the a-pawn and the two knights.
Svante Carl von Erichsen (2008-08-05 00:49:28)
The white b pawn can't be the original a pawn, because then a2 or b3 would have been blocked all the time and the new black bishop could not have gone where he is now. Also, as Normajean already noted, the b pawn can only have moved after the bishop was already made.
So, the black e pawn needs to have captured his way all the way to the a file and then to b1 and finally back out. What were these captures? The first two are easy - two white Knights. Then, the white a pawn can have been moved one to the right through a capture, and finally, the a white a rook can have been captured to get the black pawn to the a file. However, now there is no piece left to be captured for the black pawn to get to b1!
There is only one solution: the white bishop must have got out there without a pawn before him moving. That way, the queen and another rook would be available for capturing. The only way for him to get out there is to be captured. This means that the current white bishop at c1 is a promoted pawn.
Conclusion: the black e pawn captured: 2 white Knights, two white Rooks, and the white Queen to get to b1 and back out before the white b pawn ever moved. Before that, a black Knight captured both white Bishops. The white a pawn afterwards promoted to bishop and finally went to the original bishop's square.
Now, where did the white pawn promote? There are only two squares available, b8 and d8. To reach d8, the pawn would have needed 5 captures, but only 4 black pieces are missing in action (promotion never adds pieces). So, it promoted at b8, and there is only one way out of there without disturbing the black pawns: Ba7.
Nicola Lupinacci (2008-08-05 22:57:59)
Svante Carl's solution is correct. White first bishop's move is Bb8-a7
Normajean Yates (2008-08-05 23:16:20)
yes that's right.- well done Svente Carl
My try was wrong I saw - because 5 white pieces are not available for capture if my argument were right [ the white Q, f1-B and h1-R being locked in before the promotion then] :(
Svente Carl is right - well done - conveyed from me too!
Normajean Yates (2008-08-05 23:24:48)
and the difficult part was LATER!
And the difficult part (with the surprising conclusion) was AFTER what I did [and did wrongly :)]
Who but a retro-chess afficionado would have imagined that white's first B-move was Bb8-a7!
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