It's kind of puzzle but I don't have the answer : is it possible to find a non-checkmate position that could never be reached in a game ?
With respects, of course, with the number of pieces available (so no position with 20 knights pls). I am thinking more of a position than no legal position could have preceded...
What do you think ?
plenty, for example any position where one player has all its pawns in their starting position, but one bishop has been moved, or the rook is not on the first rank
oh yeah... now that you say it that seems obvious aha.
It was still an interesting question, one I hadn't thought of before. I also thought about it for a moment before reading zenagian's reply and thinking it was obvious.
I think what he said was the only answer. I at first thought of two bishops on the same color, but obviously that could be achieved by promotion.
Any position where both kings are beside each other with no squares between them.
Any position where both kings are in check.
Any position where the following is not satisfied: number of white kings = number of black kings= 1.
Just imagine a position which matches the starting position only with the black knight moved from g8 to f6. That way you at least have to think about why this could never be achieved with a series of allowed chess moves :-)
The easiest way to find one is to just start a chess 960 game, the starting position is almost certainly not attainable in a regular chess game.
Wanna something special yet stylish?
lichess.org/editor/rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR b KQkq
You might have seen this position before. Black to move^^
There should (must?) be more complex solutions to your question, e.g. a position that was forcibly preceded by stalemate or where the last move is impossible.
What about this one? Black to move (stalemate). But what was white's preceding move?
lichess.org/analysis/standard/7B/8/8/8/PPP1P3/KR1N1P2/1pRN4/k2B1Q2_b_-_-PS:
Now that I thought about it, this is also one. White to move... But where did that pesky knight come from?
lichess.org/analysis/standard/8/8/8/p1p5/3p4/1n6/3b4/K1k5_w_-_-#0White King in check and Black to move? Wtf?
