Promoting to a bishop?

Cool idea. Most examples of promoting to rook or bishop are positions where promiting to a queen would stalemate the opponent, it's nice to see that it can be also reverted.

Panagrellus

#22

@mkubecek

I came across this example in a previous Lichess forum discussion, where @ayrtontwigg posed this challenge:

"CHALLENGE:
Create a chess problem (in regular chess), where one of the moves has to be an underpromotion to a Rook or Bishop, and the purpose of the underpromotion is not to avoid stalemate. Note: The underpromotion move has to be the only correct move in the solution."

lichess.org/forum/general-chess-discussion/hardestimpossible-composition-challenge?page=1

The example above (#19, the defensive stalemate) meets the criteria of the challenge, because the purpose here is not to *avoid* stalemate, but to *force* it.
The elusive beast is a position where underpromotion to a Bishop is the only correct solution, but it has nothing to do with stalemate at all. Probably such a position cannot exist, but I'm not convinced by the previous forum posts (in the old thread I just linked) that claimed that this can be "proven logically"

mkubecek

#23

Well, the obvious part it that a queen can make any move that a bishop can so that the trick must be making an advantage from not being able to make those extra moves. Avoiding a stalemate and forcing a stalemate are clearly examples of such advantage but a proper proof that it has to be one of those is a different story. Naturally, to be able to prove such claim, one would have to start by providing an exact definition of "nothing to do with a stalemate". :-)

(Technically, the original study does not actually enforce a stalemate but uses it as a threat but that still has something to do with a stalemate.)

NM AyrtonTwigg

#24

I'm still 99.99999% sure that, if stalemate counted as a loss for the player who cannot move, then there would never be a reason to underpromote to a rook or bishop.

So, "something to do with stalemate" means that a player underpromotes to a rook or bishop to avoid stalemate and win the game, or a player underpromotes to a rook or bishop to stalemate himself and prevent a loss. Those are the only choices.

Brian-E

#25

If stalemate was a loss for the player unable to move, I think the only reason for underpromotion to rook or bishop would be psychological. Suppose the opponent was short of time, and suppose promoting to a queen would very obviously force the opponent to capture the new queen, whereas the best response to promoting to a lesser piece would not be so clear, this would give the opponent something to think about in their time trouble.

FM AuraZ0