rccall@dartvax.UUCP (R. Christian Call) (02/16/84)
< for the blank line muncher > I hope !heurikon!jeff doesn't mind me posting the solution to his puzzle on the net. I'm sure he'll let me know if he *does* mind. WARNING: read on no further if you still want to struggle with this one. 1) Mate in two. We have to consider how this position came up. Clearly, Black's QNP and KRP haven't ever moved, so he couldn't have moved one of them; and with all the material surrounding his king he couldn't have played K-K1; therefore, he must have moved either his QP or KBP, and since he couldn't have played it from Q3 or KB3, it had to be either P-B4 or P-Q4, which leaves White with an en passant capture -- PxP ep, any, P-B7 (or Q7) mate. 2) Which pawn was it? That's the real question. Consider first White's pawn structure. In order to get into that position, White must have made at least ten pawn captures. All in all, Black has lost exactly ten pieces and pawns. Therefore, all of Black's pieces and pawns were captured by white pawns. Specifically, Black's Queen Bishop must have been taken by a pawn, but in order to do so it must have left QB1. Since we know that Black's QNP has never moved, the Bishop must have moved out via Q2 -- which means that the QP must have moved. Therefore, Black's last move cannot have been P-Q4, and it must have been P-KB4. (And that's why the puzzle has only one solution.)