Frog Chess

This 10x8 chess variant resulted from my search for a 10x8 board variant that uses the standard chess army plus two pawns per side, along with an extra pair of symmetrically moving (and capturing like moving) minor pieces per side that have about the value of a N or B, again on a 10x8 board. In addition, I wanted to have no unprotected pawns in the setup. Among other things, Dr. H.G. Muller suggested to me that the frog piece type (i.e. ferz-threeleaper compound piece) might be suitable, not knowing I'd just begun to consider it seriously. After I had first thought of a setup for this variant, I discovered that it might have drawbacks, particularly due to an initial leap (i.e. on the file) by White's kingside frog. At this point Dr. Muller suggested another setup close to that one, and this became the final setup (again it was something I'd not very seriously given thought to). However, players who wish to might try using my early setup in games too, as it is not clearly infeasible.

A Game Courier preset page for play (with or without rules enforced) is available.

Setup

Note that the early setup I had for this variant is simply one with each of the adjacent frogs and bishops switched within both players' armies in the final setup shown above.

Pieces

There are 7 piece types in Frog Chess, 6 being the same as for standard chess (pawn, knight, bishop, rook, queen and king). The other piece type is the frog:

The frog is a compound piece that moves like a ferz (one square diagonally) or a threeleaper (i.e. leaps exactly three squares orthogonally, meaning on a rank or file). Note that it is not a colour-bound piece.

Rules

Castling is as in standard chess, except a king goes three squares sideways during the process (instead of two squares). Threefold repetition of position or stalemate is a draw as in chess, and similarly the 50 move rule is also in effect in Frog Chess (i.e. game drawn if no captures or pawn moves before 50 consecutive moves by both sides). Pawns move as in chess, and can promote to any piece type included in the setup, except for a king.

Notes

My tentative estimates for the piece values in Frog Chess: P=1; N=3.38(or 3.5 approx.); F=3.6(or 3.5 approx.); B=3.75; R=5.5; Q=B+R+P=10.25 and a K has a fighting value of 3.2 (though naturally it cannot be traded). Note that for standard chess, a N has been rated as high as 3.5, which I tend to agree with.

Dr. Muller's computer studies give the following minor piece values for on a 10x8 board: N=3; F=3.15; B=3.5(or 3.75 if part of a pair of Bs). Note that for standard chess, computer studies put N=3.25.

Dr. Muller has also found that on a 10x8 board with K & 2 minor pieces vs. lone K, 2 Frogs checkmate in 30 moves, F+B mate in 37, F+N mate in 39 and B+N mate in 39, all being in worst case situations for the pieces involved.

For those who might wish to have a physical 10x8 chessboard, Dr. Muller has mentioned elsewhere that a simple solution would be to cover up two ranks of a physical 10x10 chessboard. For those who might wish to search for a more elegant solution, at least in the past such boards were sold in Germany for the 10x8 variant Janus Chess (the pieces of its set could be somewhat suitable to play Frog Chess with, too). Here's a link about that game, with the specifics for ordering a set included:

Janus Chess

Note that ChessV currently supports Frog Chess.

Last revised by Kevin Pacey.