The only possible case where a pawn staying a pawn would help, that I can think of, would be in a case where you want to encourage a stalemate because the 8th-rank pawn can't move. If moving the pawn to the 8th rank exposes the opponent's king to a check, requiring the opponent to protect his King and then you have no legal move, it would a be stalemate, which may be desirable when the opponent has much more material. If this example below has a flaw (I just cooked it up), then something similar would work. The first move is the White Pawn to f8, promoting it to a Pawn - I can't show it in the diagram because it wants me to promote it to a piece!
Yyyokay.
So what does the above hafta do w/ "promoting" to a pawn ?
My apologies, I went a bit too far off topic by posting the diagram in post #82.
Not a problem. Highly instructive...TY eric
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