Shogi variant

There are a number of shogi variants played on boards larger than 9×9. These variants are all quite old, and were possibly all played without drops. Michael C. Vanier says, "It is thought that the really huge games (dai dai and up) were never really played to any significant extent [...] and were devised merely so that the creators could have the fun of inventing enormous games, amazing their friends and confounding their enemies. However, the games up to tenjiku shogi at least appear to be quite playable, assuming one has the time."[1]

The same 12th-century document which describes the Heian form of shogi also describes a variant played on a 13×13 board, which is now called Heian dai shogi (平安大将棋). As with the smaller Heian shogi, the rules for this game have not been completely preserved.

The most popular large-board variant is chu shogi (中将棋), played on a 12×12 board. The name means medium shogi, and the game is sometimes so called (or called middle shogi) in English. Chu shogi has existed since at least the 14th century; there are earlier references, but it is not clear that they refer to the game as we now know it. Chu shogi is best known for a piece called the lion, which moves like a king but twice per turn. The game was still commonly played in Japan in the early 20th century, but has now largely died out. It has, however, gained some adherents in the West. The main reference work in English is the Middle Shogi Manual by George Hodges.

Other large medieval shogi variants were wa shogi (11×11, sometimes played with drops), dai shogi (大将棋, "great shogi", 15×15), tenjiku shogi (天竺将棋, literally "Indian shogi", but meant "exotic shogi", 16×16), dai dai shogi (大大将棋, "great great shogi", 17×17), maka dai dai shogi (摩訶大大将棋, "ultra great great shogi", 19×19) and tai shogi (泰将棋, "grand shogi", 25×25). These variants date back at least to the 17th century. Tai shogi was thought to be the world's largest chess variant, but recently records of an even larger variant, taikyoku shogi (大局将棋, "ultimate shogi", 36×36), was discovered. However, there is no evidence that any of them were commonly played apart from dai shogi. While a few sets for dai dai shogi, maka dai dai shogi, and tai shogi are known to have been made, they appear to have been intended as display pieces and not for actual playing. Furthermore, the sources for the rules of almost all the larger variants tend to disagree with each other on many particular issues, even including the very moves of the pieces, such that only for chu shogi and dai shogi is it well-known what the historical rules were, and some small lacunae still arise in the latter with rare situations.

Of the historical large-board variants, only wa (11×11), chu (12×12), tenjiku (16×16), and maka dai dai shogi (19×19) have gained a limited following today. There is a society for chu shogi in Japan, as well as some efforts to revive maka dai dai shogi, though both efforts have changed the rules slightly from the historical ones – more significantly for maka dai dai shogi, unlike for chu shogi whose former popularity still lies within living memory. Tenjiku shogi gained some Western following around the turn of the millennium, although not with the historical rules.

The most recent traditional large board variant is ko shogi (廣将棋 or 廣象棋 "wide shogi", 19×19), which is played on a go board and incorporates elements of Chinese chess. Ko shogi is unusual for the interdependence of its pieces and the complex rules of promotion, but likewise there is no evidence that it was ever played.