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This page is written by the game's inventor, Jose Carrillo.

Modern Prime Ministers Chess

Prime Ministers Chess (PMC) is an adaptation of Gabriel Vicente Maura's 1968 Modern Chess (9 columns, simple reverse symmetry, symmetric castling to either side, an extra pawn, the Prime Minister (B+N) and the Bishop Adjustment Rule) to a 9x8 board.


The initial layout is identical to Maura's Modern Chess: Bishops, Knights and Rooks at the 3-leftmost and 3 rightmost squares placed just like in Orthodox Chess; the King in the middle square of the first rank (on the e-file); the Queen to the right and the Prime Minister to the left of the King. The 9 Pawns are placed on the 2nd rank.

The 9x8 board has dark squares at the corners on one of the 9-squares sides, and light squares on the other 9-squares side. It is irrelevant which side (White or Black) is playing with dark or light squares on their side.

You can play 9x8 Prime Ministers Chess on a 10x8 board (i.e. Capablanca Chess board) by covering the squares on the 'a' or 'i'-file; or on a 9x9 board (i.e. Modern Chess board) by covering the squares on the 1st or 9th rank.

Bishops start on the same color squares, but in opposite colors from one army to the next (White's Bishops may start on the light squares and the Black ones on the dark squares; or vice versa White's Bishops on the dark squares and the Black ones on the light squares). The Bishop Adjustment Rule enables the players to swap one of their Bishops to the opposite color.

While the setup described above (with Prime Minister to the left and Queen to the right of the King, and with reverse symmetry) is the original and prefered setup, the symmetry of the board allows three additional and alternate setups. The setups below are all valid Prime Ministers Chess starting layouts, for which the game can still be played under the same rules:

Note that the first alternate setup on the left also displays simple reverse symmetry, while the other two alternate setups use direct symmetry accross the board.

The code name for the main Prime Minister Chess layout (the layout same as Maura's Modern Chess) is PMC1 (or just PMC). The code names for the alternate layouts above are PMC2, PMC3 and PMC4 respectively.

When playing OTB, players can choose randomly which one of the 4 setups to play by fliping a coin twice. The first flip determines whether the game will have reverse or direct symmetry. The second flip determines whether the Prime Minister will be to the left or the right of the King. The Queen will then go on the opposite side of the King.


Orthodox Chess pieces are used, plus a Prime Minister (Bishop+Knight) and a 9th Pawn per side.

Practical Value of the Pieces (adjusted to an 8x8 board)

Gabriel Vicente Maura's Prime Minister (from his book Mathematical Thesis of Modern Chess):

Kings and their Prime Ministers

Homemade Prime Ministers

Knight crowned by small Bishop, Bishop crowned with small Knight, and a crownless King.

The Prime Minister is the only piece that is able to give a checkmate on it's own. Sample Prime Minister's checkmates:


Most Orthodox Chess rules apply, including the objective of the game, the way pieces move and capture, en passant, check, checkmate, and the various draw situations (i.e. stalemate, insufficient mating material, threefold repetition, 50-move rule). Pawns may promote to a Queen, Minister, Rook, Bishop or Knight. The Castling and the Bishop Adjustment Rules are below.


Castling in PMC is long (O-O-O) to both flanks of the board, just like in Maura's Modern Chess.

This table shows where the King and Rook end up and the notation for each type of castling.

White castles a-sidec-castlingO-O-OcKc1, Rd1
White castles i-sideg-castlingO-O-OgKg1, Rf1
Black castles a-sidec-castlingO-O-OcKc9, Rd9
Black castles i-sideg-castlingO-O-OgKg9, Rf9

Castling may only occur under the following conditions:

These rules have the following consequences:

The Bishop Adjustment Rule

Players on their turn, are allowed to convert one (and only one) of their Bishops to the opposite color square by swapping places with any piece adjacent to them. Neither the Bishop nor the piece to be adjusted with may have moved before the Bishop swap. The Bishop adjustment will count as a single turn, and a move for both the Bishop and the piece swapped with.

The Notation for the Bishop Adjustment is 'Bx <=> piece adjusting with', where x is the coordinate the Bishop is before the adjustment (i.e. Bc<=>M stands for a Bishop on the c file adjusting with the Minister).

Sample Bishop Adjustments

José Carrillo - Luis Menéndez
MRC position #2,264
May 2008


Position after 3... e6; and after 4.Ba<=>N Bg<=>M (both White and Black Adjust their Bishops on the 4th move)


Prime Ministers Chess was proposed by José Manuel Carrillo-Muñiz, from Puerto Rico, in June 2008.

Game Courier Preset

Prime Ministers Chess preset

Game Courier Logs

Game Courier Logs for Games of Prime Ministers Chess

To see actual games that have been played on-line, follow the link above.

Other Variants by the Author:

Other Pages by the Author:

List of items authored by: José Carrillo

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 Jose Carrillo.
Web page created: 2008-06-01. Web page last updated: 2008-06-01