a	b	c	d	e	f	g	h	i
9										9
8										8
7										7
6										6
5										5
4										4
3										3
2										2
1										1
	a	b	c	d	e	f	g	h	i

Modern chess starting setup. Each prime minister is to the left of its king.

Modern chess is a chess variant played on a 9×9 board. The game was invented by Gabriel Vicente Maura in 1968.^[1][2] Besides the usual set of chess pieces, each player has a prime minister and an additional pawn:

The prime minister (M) combines powers of a bishop and a knight.

The first match was played in Madrid at Escuela de Bellas Artes de San Fernando's cafe on March 18, 1968. The players were Gabriel Vicente Maura himself (White), and Bonifacio Pedraz Cabezas (Black).

Game rules

The starting setup is as shown. All the standard rules of chess apply, along with the following special rules:

• A player can castle either ministerside (notated "0-M-0") or queenside (notated "0-Q-0");^[1] in either case the king slides two squares toward the castling rook.
• When reaching the final rank, pawns can promote to one of the usual pieces or to prime minister.

Optional rule

In response to criticism that bishops are restricted to only one square color, the inventor proposed an optional new rule, if the players agree:

• One bishop may switch its position with a piece adjacent to it, provided that the bishop and the piece adjacent have not yet moved in the game. The switch is counted as a normal move.