Okisaki shogi (御妃将棋 okisaki shōgi "Queen shogi") is a modern variant of shogi (Japanese chess). It was developed by Masayuki Nakayachi c. 1996 from suggestions by German chess player Ralph Blockhaus.

Okisaki shogi is similar to standard shogi, but is played on a 10×10 board. There are ten pawns and a queen, which moves like a queen in Western chess. The knights also move as in Western chess.

Rules of the game

Game equipment

Two players, Black and White (or 先手 sente and 後手 gote), play on a board ruled into a grid of 10 ranks (rows) by 10 files (columns). The squares are undifferentiated by marking or color.

Each player has a set of 22 wedge-shaped pieces, of slightly different sizes. From largest to smallest (most to least powerful) they are:

• 1 king
• 1 queen
• 1 rook
• 1 bishop
• 2 gold generals
• 2 silver generals
• 2 knights
• 2 lances
• 10 pawns

Table of pieces

Listed here are the pieces of the game with their Japanese representation:

English speakers sometimes refer to promoted bishops as horses and promoted rooks as dragons, after their Japanese names, and generally use the Japanese name tokin for promoted pawns. Silver generals and gold generals are commonly referred to simply as silvers and golds.

The characters inscribed on the backs of the pieces to indicate promoted rank may be in red ink, and are usually cursive. The characters on the backs of the pieces that promote to gold generals are cursive versions of 金 'gold', becoming more cursive (more abbreviated) as the value of the original piece decreases. Another convention has abbreviated versions of the original characters, with a reduced number of strokes. The first version has been adopted for this article, as the abbreviated version of 跳 is not known (this piece not appearing in standard shogi).

Setup

Movement and capture

Piece moves are as in standard shogi, apart from the queen (妃将 or 妃 hishō or okisaki "princess") and the knights (跳馬 or 跳 chōma), which move as in Western chess, and the lance, which can move directly forward or backwards (standard shogi knights and lances can only move forward.) 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 (meaning 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 knight is an exception in that it does not move in a straight line.

If a pawn, which cannot retreat or move aside, advances across the board until it can no longer move, it must promote.

Some 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:

Step movers

Some pieces move only one square at a time. (If a friendly piece occupies an adjacent square, the moving piece may not move in that direction; if an opposing piece is there, it may be displaced and captured.)

The step movers are the king, gold general, silver general and the ten pawns on each side.

Jumping piece

The knight can jump, that is, it can pass over any intervening piece, whether friend or foe, with no effect on either.

Ranging piece

The bishop, rook, and queen can move any number of empty squares along a straight line, limited only by the edge of the board. If an opposing piece intervenes, it may be captured by moving to that square and removing it from the board. A ranging piece must stop where it captures, and cannot bypass a piece that is in its way. If a friendly piece intervenes, the moving piece is limited to a distance that stops short of the intervening piece; if the friendly piece is adjacent, it cannot move in that direction at all.

Promotion

A player's promotion zone consists of the three farthest ranks, at the original line of the opponent's pawns and beyond (that is, the opponent's territory at setup). If a piece crosses the board within the promotion zone, including moves into, out of, or wholly within the zone, then that player may choose to promote the piece at the end of the turn. Promotion is effected by turning the piece over after it moves, revealing the name of its promoted rank.

Promoting a piece has the effect of changing how that piece moves until it is removed from the board. Each piece promotes as follows:

• A king, a queen, or a gold general cannot promote, nor can pieces which are already promoted.
• A silver general, knight, lance or pawn, when promoted, loses its normal movement and gains the movement of a gold general.
• A bishop or rook, when promoted, keeps its normal movement and gains the ability to move one square in any direction (like a king). This means the bishop is now able to reach any square on the board, given enough moves.

If a pawn reaches the farthest rank, it must be promoted, since it would otherwise have no legal move on subsequent turns. Because they can back out, the rules in standard shogi making it mandatory to promote knights and lances in the final ranks do not apply to okisaki shogi.

Drops

Captured pieces are retained in hand, and can be brought back into play under the capturing player's control. On any turn, instead of moving a piece on the board, a player may select a piece in hand and place it—unpromoted side up and facing the opposing side—on any empty square. The piece is then one of that player's active pieces on the board and can be moved accordingly. This is called dropping the piece, or simply, a drop. A drop counts as a complete move.

A drop cannot capture a piece, nor does dropping within the promotion zone result in immediate promotion. Capture and/or promotion may occur normally, however, on subsequent moves of the piece.

A pawn may not be dropped on the furthest rank, since it would have no legal moves on subsequent turns. Because they can back out, the restrictions in standard shogi on dropping knights on the last two ranks and lances on the final rank do not apply to okisaki shogi.

There are two additional restrictions when dropping pawns, as in standard shogi:

1. Nifu (Japanese: 二歩): A pawn cannot be dropped onto a file (column) containing another unpromoted pawn of the same player (promoted pawns do not count). A player with an unpromoted pawn on every file is therefore unable to drop a pawn anywhere. For this reason it is common to sacrifice a pawn in order to gain flexibility for drops.
2. Uchifuzume (Japanese: 打ち歩詰め): A pawn cannot be dropped to give an immediate checkmate. (Although other pieces may be dropped to give immediate checkmate.) A pawn may, however, be dropped to give immediate check.

The ability for drops in okisaki shogi give the game tactical richness and complexity, as no piece ever goes entirely out of play.

Individual pieces

Below are diagrams indicating each piece's movement. Pieces are paired with their promotion. Pieces with a grey heading start out in the game; those with a blue heading only appear on the board after promotion. Betza's funny notation has been included in brackets for easier reference.

Game end

A player who captures the opponent's king or all other pieces^{[citation needed]} wins the game (unless the bared player immediately follows this baring by baring his own opponent, in which case it is a draw). 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.)

There are two other possible (but fairly uncommon) ways for a game to end: repetition (千日手 sennichite) and impasse (持将棋 jishōgi).

If the same position occurs four times with the same player to play, then the game is no contest. However, if this is the result of perpetual check, the checking player loses. For the position to be considered the same, both the board position and the pieces in hand must be identical.

The game reaches an impasse if both kings have advanced into their respective promotion zones and neither player can hope to mate the other or to gain any further material.

Game notation

The method used in English-language texts to express shogi moves was established by George Hodges in 1976. It is derived from the algebraic notation used for chess, but differs in several respects.

A typical example is P-8g. The first letter represents the piece moved: P = pawn, L = lance, N = knight, S = silver, G = gold, B = bishop, R = rook, Q = queen, K = king. Promoted pieces have a + added in front of the letter. e.g., +P for a tokin (promoted pawn). The designation of the piece is followed by a symbol indicating the type of move: - for an ordinary move and x for a capture. Next is the designation for the square on which the piece lands. This consists of a number representing the file and a lowercase letter representing the rank, with 1a being the top right corner (as seen from Black's point of view) and 10j being the bottom left corner. (This method of designating squares is based on Japanese convention, which, however, uses Japanese numerals instead of letters. For example, the square 2c is denoted by 2三 in Japanese.)

If a move entitles the player to promote the piece, then a + is added to the end to signify that the promotion was taken, or an = to indicate that it was declined. For example, Nx7c= indicates a knight capturing on 7c without promoting.

In cases where the above notation would be ambiguous, the designation of the start square is added after the designation for the piece in order to make clear which piece is meant.

Moves are commonly numbered as in chess.