Kō shōgi (廣将棋 or 廣象棋 'broad chess') is a large-board variant of shogi, or Japanese chess. The game dates back to the turn of the 18th century and is based on xiangqi and go as well as shogi. Credit for its invention has been given to Confucian scholar Ogyū Sorai.
Unlike standard shogi, pieces may not be dropped back into play after being captured. Promotion rules are complex, and the fates of several pieces are interdependent.
The objective is to capture the opponent's commanding pieces: The general, plus, if present, the governor; otherwise, the banner or middle army.
Two players, Black and White, play on a go board ruled into a grid of 19 ranks (rows) by 19 files (columns) with a total of 361 intersections.
Each player has a set of 90 pieces of 34 different types. The pieces are round and flattened like go stones. In all, the players must remember 65 different moves. The pieces are generally of the same size, though black pieces may be slightly larger than white pieces.
Each piece has its name in the form of one or two Japanese characters marked on its face, in white on black stones and in black on white stones. On the reverse side of most pieces are other characters in red; this side is turned up to indicate that the piece has been promoted during play.
Listed below are the pieces of the game and, if they promote, which pieces they promote to. *Pieces marked with asterisks are not found at setup, and only appear with promotion. Many of the translations into English are suggestions only.
Below is a diagram showing the setup of one player's pieces. The pieces are placed on the intersecting lines of the board and not in the squares. The way one player sees their own pieces is the same way the opposing player will see their own pieces.
The players alternate making a move, with Black moving first. A move consists of moving a piece on the board and potentially capturing a piece or pieces and promoting a piece or pieces. Each of these options is detailed below.
An opposing piece is generally captured by displacement: That is, if a piece moves to an intersection occupied by an opposing piece, the opposing piece is displaced and removed from the board. A piece cannot move to an intersection occupied by a friendly piece (that is, a piece controlled by the same player). However, some shooting pieces are unable to capture by displacement, and therefore cannot move to an intersection occupied by an opposing piece.