Dai shogi

Objective

The objective of the game is to capture the opponent's king and, if present, the prince, which counts as a second king; or to capture all the other pieces leaving a bare king or bare prince. Unlike standard shogi, pieces may not be dropped back into play after capture.

Game play

Two players alternate, making a move with Black moving first. (The pieces are not differentiated by color; the traditional chess terms "Black" and "White" are only used to indicate who plays first, and to differentiate the sides during discussions of the game.) A move consists of moving a piece either to an empty square on the board or to a square occupied by an opposing piece, thus capturing that piece; and optionally of promoting the moving piece, if the move enters the promotion zone, or if it is a capture and any part of it is in the promotion zone.

Game equipment

Two players, Black and White (or 先手 sente and 後手 gote), play on a board ruled into a grid of 15 ranks (rows) and 15 files (columns) with a total of 225 squares. The squares are undifferentiated by marking or color, unlike a Western chess board.

Each player has a set of 65 pieces of 29 different types. In all, a player must remember 36 different moves. Each piece has its name written on it in Japanese kanji. The writing is typically in black. On the reverse side of most pieces there are characters to indicate the piece's promoted rank, typically written in red. The pieces are wedge-shaped and their orientation indicates which player they belong to, as they point toward the opposing side. The pieces are of slightly different sizes, from largest to smallest (most to least powerful) they are:

Listed below are the pieces of the game and, if they promote, the pieces they promote to. Names are rough translations that have become somewhat standardized in English. Pieces are listed alphabetically by their English name.

The promotions apply only to pieces which start out with the ranks in the left-most column, that is, pieces with these ranks written in black; promoted pieces with those same ranks written in red may not promote further. Pieces which only appear upon promotion, that is, names which only occur written in red, are marked with an asterisk. The king, queen, and lion do not promote.

¹ The pronunciations of 龍馬, 奔王, 反車, and 白駒 are irregular. The regular forms ryūme, hon’ō, hansha, and hakuku are also seen.

Setup

Below is a diagram showing the initial setup of the board.

Movement and capture

An opposing piece is captured by displacement: That is, if a piece moves to a square occupied by an opposing piece, the opposing piece is displaced and removed from the board. A piece cannot move to a square occupied by a friendly piece, that is, by another piece controlled by the moving player.

Each piece on the game moves in a characteristic pattern. Pieces move either orthogonally (that is, forward, backward, left, or right, in the direction of one of the arms of a plus sign, +), or diagonally (in the direction of one of the arms of a multiplication sign, ×). The lion and knight are exceptions in that they do not move, or are not required to move, in a straight line.

Many pieces are capable of several kinds of movement, with the type of movement most often depending on the direction in which they move. The movement categories are:

Promotion

The promotion zone is the 'enemy camp', the farthest five ranks of the board, which are mostly occupied by the opposing player's pieces when the board is first set up. When a promotable piece makes a move entering the promotion zone, or makes a capture within the promotion zone—including moves entering, leaving, or moving entirely within the zone—it has the option of "promoting" to a more powerful rank. Promotion is effected by turning the piece over after it moves, revealing the name of its promoted rank. Promotion is not mandatory if the unpromoted piece could move further on a later turn, and in some cases it may be beneficial to leave the piece unpromoted. Promotion is permanent and promoted pieces may not revert to their original rank. If a piece is not promoted upon entering the promotion zone, then it may not promote until it leaves the zone and reenters unless it makes a capture.

Promoting a piece has the effect of changing how that piece moves. See below.

If a piece that cannot retreat or move aside advances across the board until it reaches the other side, it is trapped. This applies to the pawn, stone general, iron general, knight, and lance. This would hardly occur in practice, because all of these but the knight promote to pieces that keep their old moves, and stalemate is a loss for the stalemated player. The situation of the knight is unclear, as it promotes to a piece that does not keep its old moves, and thus there could be a reason to defer its promotion. In chu shogi, which is descended from dai shogi, this situation applies to the pawn, which therefore gets a second chance to promote at the last rank on a non-capture: this second chance can likewise be declined, leaving the pawn as an immobile "dead piece" (死に駒). Whether this rule applies to the knight in dai shogi is uncertain, both because this rule might be a later refinement to chu shogi, and because the Edo-era sources have numerous lacunae when describing the rules of the variants other than sho shogi and chu shogi.

The promotion rules of dai shogi may have changed significantly over time. The promotion rules in the earlier Heian shogi and Heian dai shogi provide for all weak stepping pieces to promote to the gold general, which is true for sho shogi and modern shogi. However, in chu shogi many of these pieces have changed promotions to ranging pieces in the initial setup. Dai shogi has a mixture of these rules: the weak steppers or limited rangers unique to dai shogi all promote to the gold general, but those present in chu shogi keep their promotion from the latter game. It is likely that these differing promotions in chu shogi are a later historical innovation, that was later copied back into dai shogi when chu shogi became more popular than dai shogi.

Individual pieces

Following are diagrams that indicate the movement of each piece. Pieces are listed roughly in order, from front to back rows, with pieces making similar moves paired. Pieces with a grey heading start out in the game; those with a blue heading only appear on the board as a promoted piece. Betza's funny notation has been included in brackets for easier reference, with the extension that the notation xxxayyyK stands for an xxxK move possibly followed by an yyyK move, not necessarily in the same direction. Larger numbers of 'legs' can be indicated by repeated application of 'a'. By default continuation legs can go into all directions, but can be restricted to a single line by a modifier 'v' ("vertical", interpreted relative to the piece's current position on its path). The default modality of all legs is the ability to move and capture: other possibilities are specified explicitly. Square brackets are used to make it clear what operators the a modifier chains together: thus DaK would denote a dabbaba move followed by a king move, but D[aK] would denote a piece that can move as a dabbaba, or twice as a king.

Repetition

A player may not make a move if the resulting position is one that has previously occurred in the game with the same player to move. This is called repetition (千日手 sennichite). Note that certain pieces have the ability to pass in certain situations (a lion, when at least one square immediately adjacent to it is unoccupied, a horned falcon, when the square immediately in front of it is unoccupied, and a soaring eagle, when one or both of the two squares immediately diagonally in front of it are unoccupied). Such a pass move leaves the position unchanged, but it does not violate the repetition rule, as it will now be the turn of the other player to move. Of course, two consecutive passes are not possible, as the first player will see the same position as before. However, evidence from historical chu shogi mating problems suggests that this prohibition does not apply to a player who is in check.

Check and mate

When a player makes a move such that the opponent's only remaining royal (king or prince) could be captured on the following move, the move is said to give check; the king or prince is said to be in check. If a player's king or prince is in check and no legal move by that player will get it out of check, the checking move is also mate, and effectively wins the game.

Unlike Western chess, a player need not move out of check in dai shogi, and indeed may even move into check. Although obviously not often a good idea, a player with more than one royal may occasionally sacrifice one of these pieces as part of a gambit.

Game end

A player who captures the opponent's sole remaining king or prince wins the game. In practice this rarely happens, as a player will resign when checkmated, as otherwise when loss is inevitable.

A player who makes an illegal move loses immediately. (This rule may be relaxed in casual games.)