Taikyoku shogi

Taikyoku shōgi (Japanese: 大局将棋; lit. "ultimate shogi") is the largest known variant of shogi (Japanese chess). The game was created around the mid-16th or 17th centuries (presumably by priests) and is based on earlier large board shogi games. Before the rediscovery of taikyoku shogi in 1997, tai shogi was believed to be the largest physically playable chess variant ever. It has not been shown that taikyoku shogi was ever widely played. There are only two sets of restored taikyoku shogi pieces, one of which is held at Osaka University of Commerce. The only played game in recent history was played in 2004 for the Japanese television show Fountain of Trivia, which took 32 hours and 41 minutes, spanning over three days, and a total of 3,805 moves.

Because the game was found only recently after centuries of obscurity, it is difficult to say exactly what all the rules were. Several documents describing the game have been found; however, there are differences between them. It is not clear how accurate the rules given by modern sources for the game are, because many of the pieces appear in other shogi variants with a consistent move there, but are given different moves in taikyoku shogi. The board, and likewise the pieces, were made much smaller than usual for the other variants, making archaeological finds difficult to decipher. Research into this game continues.

Taikyoku shogi is very different from other large-board shogi variants: tenjiku shogi, dai dai shogi, maka dai dai shogi, and tai shogi. The most notable differences lie with the piece movements and their promotions.