Neutral King Chess is a variant of Orthochess that was invented by V.R. Parton in 1953. It is played with the usual Chess pieces, but there are no Queens, and only one King, which is Neutral, and may be moved by either side. The object is to checkmate the lone King. Neutral King Chess is described in Pritchard's Encyclopedia of Chess Variants.
Each side starts with six Pawns and six pieces, and there is a King belonging to neither.
+---+---+---+---+---+---+---+---+ 8 | r |:b:| n |:p:| |:::| |:::| +---+---+---+---+---+---+---+---+ 7 |:r:| b |:n:| p |:::| |:::| | +---+---+---+---+---+---+---+---+ 6 | p |:p:| p |:p:| |:::| |:::| +---+---+---+---+---+---+---+---+ 5 |:::| |:::| |:::| |:::| k | +---+---+---+---+---+---+---+---+ 4 | |:::| |:::| |:::| |:::| +---+---+---+---+---+---+---+---+ 3 |:P:| P |:P:| P |:::| |:::| | +---+---+---+---+---+---+---+---+ 2 | R |:B:| N |:P:| |:::| |:::| +---+---+---+---+---+---+---+---+ 1 |:R:| B |:N:| P |:::| |:::| | +---+---+---+---+---+---+---+---+ a b c d e f g h |
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The rules of Neutral King Chess are identical to those of International Chess, except when noted below.
The goal of the game is to checkmate the Neutral King.
This game can easily be played with a standard Western Chess set. Just choose one of the Kings and remember that is is neutral. It may be easier, however, to use a King from a different set whose color does not match either of those used for the other pieces.
This is a nice playing game, and unusually completely specified for a V.R. Parton design. It does seem to me that it could, however, benefit from a Ko rule, like that used in Go. That is, a move that returns the board to the exact same configuration that it had at the beginning of the previous player's move is not allowed. In other words, if one player makes a non-capturing move with the King, the other player may not on the immediately following turn move it back to the square it just came from.
This information is based on the description in Pritchard's Encyclopedia of Chess Variants.
There is an implementation of Neutral King Chess for Zillions of Games (both with and without a Ko rule). You can download it here:
Ed Friedlander has written an applet that lets you play Neutral King Chess against your computer. To play, click here.