Кіші сёги: Жапон шахматының көне түрі

Shō shōgi (小将棋 'small chess') is a 16th century form of shogi (Japanese chess), and the immediate predecessor of the modern game. It was played on a 9×9 board with the same setup as in modern shogi, except that an extra piece stood in front of the king: a 'drunk elephant' that promoted into a prince, which is effectively a second king. While 9×9 may not seem 'small', it was smaller than the other shogi variants prevalent at the time, which were the 12×12 chu shogi and 15×15 dai shogi. According to the Sho Shōgi Zushiki, the drunk elephant was eliminated by the Emperor Go Nara (reigned 1526–1557), and it is assumed that the drop rule was introduced at about the same time, giving rise to shogi as we know it today.

The objective of the game is to capture your opponent's king and crown prince (if present) or all other pieces.

The players alternate making a move, with Black moving first. (The traditional chess terms 'black' and 'white' are used to differentiate the sides during discussion of the game in English, but are not literally descriptive. In Japanese, the side moving first is referred to as 先手 sente, and the second player is referred to as 後手 gote.) A move consists of moving a single piece on the board and potentially promoting that piece or displacing (capturing) an opposing piece. Each of these options is detailed below.

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 lance or pawn, pieces that 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:

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, drunken elephant, gold general, silver general and the 9 pawns on each side.

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

The bishop and rook 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.

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 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 drunken elephant, 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, knight or lance reaches the farthest rank, it must be promoted, since it would otherwise have no legal move on subsequent turns.

When a player makes a move such that the opponent's king or crown prince could be captured on the following move, the move is said to give check to the king or crown prince; the king or crown prince is said to be in check. If a player's king or crown prince (sole one in play) is in check and no legal move by that player will get the king or crown prince out of check, the checking move is also mate, and can effectively win the game. A player is not allowed to give perpetual check.

A player who captures the opponent's king and crown prince (if present) wins the game, as does a player who captures everything else, leaving a "bare" (or lone) king or crown prince. 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 is one other possible (but fairly uncommon) ways for a game to end: repetition (千日手 sennichite). If the same position occurs four times with the same player to play, then the game is no contest. (Recall, however, the prohibition against perpetual check.)

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 8f. The first letter represents the piece moved: P = pawn, L = lance, N = knight, S = silver, G = gold, B = bishop, R = rook, DE = drunken elephant, 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 9i 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. For example, the start of a game might look like this:
1. P 7f P 3d
2. P 2f G 3b
3. P 2e Bx8h+
4. Sx8h S 2b