Chess variant

Did You Know?

• In The Chessmen of Mars, Edgar Rice Burroughs describes Jetan, a game depicting a war between two races of Martians.
• Chess boxing, a hybrid sport of chess and boxing, was depicted in a 1992 comic by Enki Bilal and later developed into a real sport.
• The Doctor Who episode 'The Wedding of River Song' depicts 'Live Chess', which introduces potentially lethal electric currents into the game.

Overview

The number of chess variants is vast, with thousands in existence. While some regional forms have histories as long as or longer than standard chess, most variants are modern creations by individuals or small groups seeking new twists on the traditional game. These variants can also spawn their own offshoots; for instance, Capablanca chess has led to many adaptations, and Horde chess is itself a version of Dunsany's Chess. Many variants were designed to solve a perceived problem with orthodox chess.

Chess960, also called Fischer random chess, was created by grandmaster Bobby Fischer to reduce the heavy influence of opening theory by randomizing the starting positions of pieces on the back ranks. A similar goal motivated José Raúl Capablanca, a Cuban world champion, who developed Capablanca chess. This variant introduces two new pieces, the marshal and the cardinal, which had previously appeared in Pietro Carrera's 17th-century chess variant.

Some modern variants are produced and sold as commercial board games, such as Icehouse: The Martian Chess Set, Omega Chess, and Chessplus. In the area of chess composition, certain variations are made not for full games but for crafting interesting puzzles, a field known as fairy chess. Fairy chess also gave rise to the term "fairy chess piece," which broadly describes any piece with movement rules different from standard chess pieces. Standardized notation systems have been created to describe these movements systematically.

A common feature of many chess variants is the inclusion of one or more fairy pieces, and physical models of popular fairy pieces are available from major chess set suppliers.

History

The chess family of board games began with chaturanga in India during the Gupta Empire. As the game spread, different regions adopted their own rule changes. In Sassanid Persia, a modified version called shatranj emerged, and it was this form that reached Europe through Arab contacts, especially in Spain. Meanwhile, chaturanga continued to evolve in India, with new rules and starting setups appearing over time.

Variants like the four-player chaturaji and the asymmetrical sarvatobhadra developed from it. Later Indian variants included a 14x14 board game described in the Harihara chaturaga of Prataparudra of Odisha, as well as Hyderbarad decimal chess on a 10x10 board and Hyderbarad shatranj kabir on a 12x12 board. Shatranj itself had several historical variants. One was complete shatranj, or shatranj al-tamma, which used a 10x10 board and introduced the dabbaba piece, a siege engine.

Islamic chess treatises often discussed these variants alongside classic shatranj for centuries. In the Shahnameh, Ferdowsi mentions a 10x10 shatranj variant that used a camel piece instead. Other 10x10 variants from the Muslim world included citadel chess, or shatranj al-husun, which added four extra squares at the board’s corners, giving the king a place to retreat. Another ancient Islamic variant was Byzantine chess, known in Arabic as shatranj ar-rumiya, an early form of circular chess. Some versions of this circular chess also included four citadels in the center.

Play

Unlike traditional chess, shogi, and xiangqi—which boast professional circuits and amateur tournaments—most modern Western chess variants are played casually. That said, a few have seen notable competitive events. Gliński's hexagonal chess held several tournaments during its peak in the 1970s and 1980s. Chess960 has also featured in tournaments, including an unofficial world championship match in 2018 between Magnus Carlsen and Hikaru Nakamura, plus official FIDE world championships in 2019 and 2022.

Crazyhouse has hosted prize-funded unofficial world championships on Chess.com and Lichess, attracting top grandmasters and experts. The Mind Sports Olympiad has run competitions for multiple chess variants. Online play is supported by servers like Chess.com, Lichess, and the Free Internet Chess Server. Software such as Zillions of Games and Fairy-Max can handle many variants.

Some chess engines also play a handful of them: the Lichess version of Stockfish, for instance, supports Crazyhouse, King-of-the-hill, Three-check chess, Atomic chess, Horde chess, and Racing Kings. Zillions of Games includes an AI that can play almost any correctly programmed variant to a reasonable standard. A few variants, like 5D Chess with Multiverse Time Travel, are impractical or impossible to play physically and exist mainly as video games.

Analysis and study

Most chess variants are similar enough to standard chess that their games can be written down using algebraic notation, though extra symbols are often needed. For instance, Millennium 3D Chess adds a third dimension, so a move like N2g3 indicates a knight moving to the g3 square on the second level. When fairy chess pieces appear, notation requires assigning new letters to represent them. Several publications have covered these games.

Variant Chess magazine, an official publication of the British Chess Variants Society from 1997, ran from 1990 to 2010, introducing many variants and offering detailed analyses. The Italian association of heterodox chess, A.I.S.E., founded in 1978 by Mario Leoncini, also released material on many variants. The more recent Abstract Games magazine discusses chess variants as well. A key figure in the field was David Pritchard, who wrote several books on the topic.

His most important work was an encyclopedia cataloging thousands of different games. After Pritchard died in 2005, John Beasley completed and published a second edition titled The Classified Encyclopedia of Chess Variants. A 2017 book, A World of Chess, provides a recent survey of historical and some modern variants. The Chess Variant Pages website, created by Hans Bodlaender in 1995, offers a growing catalog of variants, a broad collection of rules, and an encyclopedia of fairy pieces.

A handful of chess variants have been heavily studied by computers. Los Alamos chess, a 6x6 variant created in 1956 specifically for computers, was simple enough for the MANIAC I computer to play. Its victory over a beginner marked the first time a computer won a chess-like game against a human opponent. In contrast, Arimaa was designed in 2003 to be easy for humans but hard for computers, though by 2015 computers had surpassed human players.

While standard chess has not been solved, some simpler variants have been. Gardner's Minichess, played on a 5x5 board, has been weakly solved as a draw. A lengthy analysis of losing chess also weakly solved it as a win for white.