Originally posted by Jirakon
I'm thinking the black h pawn promoted on g1 to a rook and everything white left that rank. Then the new black rook got to d6, the white bishop captured it, the black e pawn captured the bishop, and the white pieces went back to rank 1. I don't have time to try it out though.
The problem is: how do you get past wPg and wPh without one of them capturing? And even assuming that difficulty can be solved, if I ...hxg2, wB is still on f1, and Pg2 will be forced to capture it [or Rh1] next. If I take further up the board, wPh2 has to capture as soon as I step on g3.
A White promotion has the same problem. I almost need to play gxh7 to get past h6, which is permanently guarded by Pg7, but the minute I land on g6, ...hxg6 is forced unless I have another capture. As if that weren't enough trouble, bRh8 is trapped in the NE corner if ...exd6 has not yet been played. wP would have to capture it if it's on g8, and it would have to capture wPh7 if it's on h8.
One long shot is that somehow a P could sneak through with discovered check. The other side could then get out of check instead of capturing. I can't find any good checks yet, though.