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This page is written by the game's inventor, Charles Gilman.

Decimal Quadruple Besiege

After Quadruple Besiege Chess I found that there were two ways of extending the principle to East Asian games and variants thereof, one for single sets on 2 7x7 boards and one for double sets on 2 9x9 boards. It has since occurred to me that two 10x10 boards can be used for a double-size version of my 30-piece Échecs De L'Escalier sets. There are four extra Pawns aside, but to compensate numbers of pieces with both orthogonal and diagonal moves are not doubled.


The two boards have two left-to-right joins, one of which is shown in the diagram below (the other can be imagined easily enough) and two top-to-bottom ones. Note that the latter join the top of the diagram's left half to the bottom of its right half and vice versa.


All pieces have extrapolations of their FIDE moves, but as only one of the four joins can be represented physically some guidance might be useful.
The PAWN moves orthogonally except when capturing, which it does diagonally. It always moves one cell. Pawns start moving toward the nearest join, and can never reach or cross their own long diagonals unpromoted. On crossing the join they move away from the nearest join. They can capture across an enemy long diagonal in either direction, including reversing a previous move if an enemy moves to the vacated cell. A Pawn actually on an enemy long diagonal may make a noncapturing move away from either nearest join, but capture only inward along the long diagonal. There are 24 Pawns aside.
The ROOK moves up to 19 steps orthogonally through empty cells. Unblocked, or blocked by only one piece per orthogonal, it can reach any cell on the orthogonals where it starts on both FIDE boards, including the intersection on the other board but not a null move to the cell where it starts. It is blocked from entering the other board from above/below/the left/the right by any piece below/above/right of/left of itself on its own board. It takes at least two pieces to block a Rook from a cell completely, four to block it from the other intersection. There are 8 Rooks aside.
The BISHOP moves up to 9 steps diagonally through empty cells. Using any one join and imagining the opposite one, any diagonal can be easily visualised as 10 cells of the same colour in a line, like a FIDE long diagonal, each diagonal then wrapping round on itself (not, as might be expected, on the one furthest from it). Unblocked, or blocked by only one piece per diagonal, it can reach any cell on the diagonals where it starts, except a null move to the cell where it starts. It takes at least two pieces to block a Bishop from a cell completely, four to block it from the other intersection. There are 8 Bishops aside.
The KNIGHT makes a 2:1 leap, which in this geometry is the same as a 9:8, 11:8, 12:9, 18:1, or 19:2 leap. Any leap that is visibly one of these on a board with one join is valid. Nothing can block a Knight. Note that 8:1, 9:2, 11:2, 12:1, 18:9, and 19:8 are not valid Knight moves. There are 8 Knights aside.
The QUEEN combines the Rook and Bishop as described above. There are 2 Queens aside.
The MARSHAL likewise combines Rook and Knight and the CARDINAL Bishop and Knight. There are 4 of each aside.
The ACE combines Rook, Bishop and Knight. There is 1 Ace aside.
The KING moves one cell orthogonally or diagonally, including between the top and bottom or left and right edges of opposite boards or between opposite corners of the same FIDE board. On two boards with one physical join this can be envisaged as 1:0, 1:1, 9:9, 10:9, 19:0, and 19:1 leaps - but not 9:0, 10:0, 9:1, 10:1, or 19:9. There is 1 King aside.


There is no initial double-step move, En Passant, or Castling.

Pawns reaching a non-Pawn's starting cell are promoted to any capturable compound array piece.

Checkmate and Stalemate are as in FIDE Chess.

This 'user submitted' page is a collaboration between the posting user and the Chess Variant Pages. Registered contributors to the Chess Variant Pages have the ability to post their own works, subject to review and editing by the Chess Variant Pages Editorial Staff.

By Charles Gilman.
Web page created: 2009-11-14. Web page last updated: 2016-03-22