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Is there any position, where moving a pawn to last rank but not promoting it to any piece would be the best move?

By the way, I know this is an illegal move. Assume it is legal.

Edit: Now we have a nice answer from Dag Oskar which ends with stalemate. That's good. But I wonder, if there is winning position, winning by not promoting, and the only winning move is not promoting.

Edit #2: I think a winning position is impossible, as this seems to be occurable when opponent stalemates with promotion. If opponent is not stalemating, then there is no point of not promoting anyway. But if opponent stalemates with a knight, then bishop or rook doesn't stalemate, and etc. It's impossible to have a position where knight, bishop and rook stalemates. So, in every such position, there will be a correct promotion. Not promoting won't be the best move anyway.

Therefore, I'm accepting the answer.

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up vote 17 down vote accepted

Here is an example:

[fen "8/4P3/8/4p1p1/2p3Pp/p4p1K/k1p2P1P/8 w - - 0 1"]

1. e8 leads to stalemate next move, while all legal promotions lose to 1... c1=Q followed by 2... Qf1#.

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2  
Good one. So, it makes sense because promoting enables moving, but a pawn on last rank can't move, so introduces stalemate ideas. I wonder if theres a position wins by not promoting. – Saibot Jan 5 at 22:53
    
Yup, this works. Same idea with 7 units instead of 13: move bKa2 to g1 and you can remove two White pawns (f2,h2) and four Black (a3,c4,e5,f3). 1 c8Q c1Q 2 Qb5(f7,f8) stops Qf1# but 2 . . . Qe3+ mates (and even 2 . . . Qf1+ still wins). – Noam D. Elkies Jan 7 at 1:06
    
@NoamD.Elkies Can you confirm that a position where not promoting would be the only winning move is impossible? – Dag Oskar Madsen Jan 7 at 1:26
2  
Actually constructing such a position is very difficult but not impossible. Your argument shows that at least some of the promotions cannot result in immediate stalemate, but stalemate can still be forced later. The first example I know was constructed about 15 years ago by Matt Bengtson and published in Hochberg's Chess Braintwisters. I can't find the position immediately but can ask Matt for it. – Noam D. Elkies Jan 7 at 3:36
    
@NoamD.Elkies That would have been great. I'm really curious about how such a position looks like. – Dag Oskar Madsen Jan 13 at 12:36

The Matt Bengtson problem Prof. Elkies mentions is:

[Title "Matt Bengtson, Chess Braintwisters (Burt Hochberg), no. 103. White to move & draw."]
[fen "4kn2/3p1pPp/4pPpK/6P1/8/2p5/1b6/8 w - - 0 0"]

1.

The start of the solution-line can't be shown in PGN as White's 1st move is illegal: 1. g8=Black queen Qg7+ (anything else stalemates White) 2. fxg7 c2 3. g8=Q c1=Q 4. Qxf7+ Kd8 5. Qe8+ Kc7 6. Qc8+ Kb6 (Kd6 7. Qc5+) 7. Qc6+ Ka7/Ka5 8. Qb7/Qb5, drawing. White's queen is then taken for stalemate. Solution line taken from Chess Braintwisters.

(This is in answer to a comment by Prof. Elkies to Dag Oskar Madsen's answer, but, it seems, the syntax that activates the PGN-viewer in answers doesn't do so in comments.)

A similar oddity from the same book:

[Title "John Beasley, EBUR, 1996. White to move & win."]
[fen "5r1K/2k1P3/3N1Bqp/N2Q1B1P/8/8/8/1R6 w - - 0 0"]

This problem was reprinted as no. 107 in Burt Hochberg's Chess Braintwisters.

White is in check, and his only reasonable move is to capture on f8 (1. Qg8? Qxg8#). But 1. exf8=R allows stalemate after 1. ... Qg7+ because the new rook guards d8 after 2. Bxg7. Similarly, 1. exf8=N guards d7 allowing 1. ... Qh7+ and stalemate, and 1. exf8=Q/B guards d6 allowing 1. ... Qg8+ and stalemate. The answer is 1. exf8! (no promotion). Now 1. ... Qg7+ 2. Bxg7 releases d8; 1. ... Qh7+ 2. Bxh7 releases d7; 1. ... Qg8 2. Qxg8 releases d6. 1. Qxf6+ destroys the stalemate at once, and White wins. Solution line and discussion taken from Chess Braintwisters.

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This cannot be the position. The question is not about promoting to the wrong color, it's about not promoting at all. – Dag Oskar Madsen 9 hours ago
1  
The second position seems to be the real deal, though. Amazing that it's possible! – Dag Oskar Madsen 8 hours ago

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