Ken Regan's Tandem Pawn Chess

by Kenneth Regan
2/13/2014 – "Some years ago Frederic Friedel of ChessBase asked for a game that was reasonably like chess but would give humanity a chance against today's computers," writes IM Ken Regan, Associate Professor at the University of Buffalo, NY. He has produced a new chess variant in which two pawns are strapped together initially. The aim is to make a game that is harder for computers to play.

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Tandem Pawn Chess

I read the ChessBase news article "A New and More Challenging Chess Variant" with interest. Azlan Iqbal proposes a variant that is designed to rekindle the interest of computer scientists in chess programming – and be enjoyable to humans as well. His "Switch-Side Chain-Chess" features just one simple rule in addition to that of the real game: either player has the option of switching armies with the opponent should a ‘chain’ (i.e. a link of pieces of any colour) form on the board. Overall this is a fun idea. However, in my opinion there should be a limit on the number of times one can switch sides. This makes conserving one's "turnabouts" a long-term strategic factor, which would in turn make the game more computer-resistant – while avoiding lengthening the game tree even more than with unlimited switches.

IM and Associate Professor of Computer Science Ken Regan

Tandem Pawn Chess, a chess-like game that favors human-type thinking, is my first attempt to fit the bill, by emphasizing longer-range pawn play.

The setup is the same as standard chess, except every pawn is a "tandem" of two pawns, which may decouple or stay yoked on any move. Tandem pawns may be made by taking two pawns of a somewhat smaller size, so both will fit in the square, optionally yoking them together with a twist-tie.

  • A tandem may move one or two squares on its first move, or one of its members may move one or two squares.

  • A tandem may capture a piece or single pawn either with both pawns moving and staying yoked, or with just one making the capture and then being protected by the other.

  • A tandem may capture a tandem, however, only by moving both pawns. These capture rules are also in effect for en-passant captures by tandems.

  • A single pawn or any other piece may capture a tandem with no restrictions.

  • Pawns cannot (re-)couple back into tandems.

  • A tandem can promote like an ordinary pawn, and both members are replaced by the new piece. Note also that just one of the tandem may elect to move and promote; this still leaves a single pawn on the seventh rank.

Finally there is one special move, called a "rocket move": If the square behind and two squares before a tandem are not occupied, the tandem may decouple with one pawn moving one step backward and the other two steps forward. The rocketing pawn must move two squares not one, and cannot be captured en-passant. Thus a tandem can threaten to promote from the sixth rank. A rocket move can also leave a pawn on the first rank. This pawn is entitled to move two squares forward from there, and also to move two squares if it has advanced to the second rank by move or capture, with en-passant rules in effect in both cases.

These rules imply that if a position is legal in standard chess, having no tandems, then the play and applicable rules from that position forward are the same as in standard chess.

The intent of Tandem-Pawn Chess is to create more considerations for positional play. In particular, minor pieces are less valuable when hemmed in by double ranks of decoupled pawns. The game also creates new vistas for pawn storms and endgame studies. Sacrifices of minors for two pawns, or better a tandem plus a single pawn, may more frequently be advantageous.

There are to date no computer implementations of the game. Frederic Friedel of ChessBase has asked for a game that was reasonably like chess but would give humanity a chance against today's computers. The aim of Tandem Pawn Chess is to make a game that is harder for computers to play relative to humans.

Kenneth W. Regan, Amherst (Buffalo) NY USA

See also

2/2/2014 – A new, challenging chess variant
Ever since desktop computers can play at its highest levels and beat practically all humans, the interest of the Artificial Intelligence community in this game has been sagging. That concerns Dr Azlan Iqbal, a senior lecturer with a PhD in AI, who has created a variant of the game that is designed to rekindle the interest of computer scientists – and be enjoyable to humans as well: Switch-Side Chain-Chess.

Kenneth W. Regan is an Associate Professor in the Department of Computer Science and Engineering at the University at Buffalo, The State University of New York. He is also an International Master in chess with a peak rating of 2409 (in July 2011).


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