Originally posted by AlethiaNumber of white pawns, the pawn structure (number of captures needed for its to happen) and number of missing(captured) black pieces. The third knight needs to be promoted from somewhere, and there just aren't enough pieces that might have been captured to get it to last rank.
Actually I guessed it was something to do with the fact the pieces could never get to that position.
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Originally posted by AlethiaI believe that was taken out of an actual game.
So you are right. The actual solution is dxe8=R K? 0-0-0-0!
At the time castling rules stated that as long as the Rook and King are unmoved, the king may moves two squares towards the rook and the rook moves to the other side of the king. After this FIDE changed the rules to only allow castling along the back-rank.
Question: What would you call this new castle if you had to name it? I'd call it castling fileside 🙂.