6

I was looking at minimal combinations of material needed to force checkmate (K+R, Q+B, R+N+N, etc). You end up with a sort of threshold of how much material is needed, and that sort of assigns a strength to the king. But that made me wonder if K+K is sufficient material to force checkmate. Obviously this is normally impossible, but in the hypothetical endgame where white has two kings and black has one (and make the obvious loosenings of the restrictions on moving into check), could the two kings force checkmate against the one king?

Alternatively, one could think of it as white having a king and a fairy chess piece that moves exactly like a king. Is this enough material to force checkmate?

  • 8
    This question doesn't make sense using the Laws of Chess. A king cannot check another king, because that would involve putting itself in check, which is illegal. Of course, it is also illegal for a player to have more than one king. Since you mention using a non-standard piece, you are introducing the idea of an undefined chess variant. If you would like to specify the rules for the chess variant, you might get some replies. At the moment, there is no reasonable way to answer this question. – jaxter Jan 30 '17 at 22:22
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    I'm not sure why this was closed. This is a totally sensible question in the context of Fairy Chess, which I've always thought was on-topic here. – Steven Stadnicki Jan 31 '17 at 20:37
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    Specifically: "Questions about variants may or may not be accepted, depending how far removed from the standard game it is. In general, a variant which uses the same board and pieces as standard chess is an on-topic subject." This is clearly a variant using the same board and pieces. – Steven Stadnicki Jan 31 '17 at 20:42
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    @StevenStadnicki I oppose to reopen. This is not a variant, this is not chess. Anyway, there is an accepted answer so nothing we should do. – SmallChess Feb 1 '17 at 2:21
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    @StudentT I disagree emphatically - as I said, there are numerous fairy chess stipulations involving multiple kings. See, for instance, matplus.net/milanvel/FairyKings.pdf or jsbeasley.co.uk/encyc/175183.pdf . – Steven Stadnicki Feb 1 '17 at 5:50
14

If these are two real kings, it is not possible.

One requirement of checkmate is that the black king is in check which cannot be achieved with any of the white kings (because it would put the white king into check).

If you say that white has only one king and a "nonstandard chess piece that moves exactly like a king" (i.e. this piece can be put next to the enemy king), then yes, it seems possible and quite easy to mate the black king. Put the two kings for instance on c3 and f3, the black king on d5. As you can see the two kings almost cover the whole 4th rank. Pushing the black king to the side of the board and into the corner is quite easy, e.g. if black starts with 1. ... Ke5, 2. Kc4 Kd6 3. Kf4 Ke6 4.Kc5 ..... Once you have the black king around the corner you put white's real king on c3, f3, f6, c6 (depending on which corner) and mate with the "nonstandard chess piece" on one of f7, g7, g6; f2,g2,g3;b3,b2,c2;b6,b7,c7.

  • There must be typo a typo in the sequence "1. ... Ke5, 2. Kf4 Kd6"... – Evargalo Feb 14 '18 at 14:35
12

A King and a Man (or commoner; i.e., a non-royal King) can mate a lone King. The longest distance to mate on a standard 8x8 board is 18 moves.

The result quoted above was obtained by H.G. Muller in 2008, see this coment on chessvariants.com: http://www.chessvariants.com/index/listcomments.php?id=28770

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    Muller certainly got the result but I can't imagine that this wasn't already known earlier; I'd be a little surprised if the result (plus or minus a move or two) wasn't already known to T.R. Dawson or one of his compatriots in the early 20th century. – Steven Stadnicki Feb 3 '17 at 8:02
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    I just wanted to source my number, I didn't do deeper research in priority. – jknappen Dec 19 '18 at 17:08

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