GNU Shogi manual: The rules of shogi

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### 2.1 The rules of shogi

Shogi is a two-person abstract strategy board game with full information (i.e. all pieces and moves are visible to both players at all times). It is in the chess family, being descended from the same ancestral game as international chess: the Indian game of Chaturanga. The two players are referred to as “Black” and “White”, with Black moving first (unlike in international chess, where White moves first), and with movement alternating between the two players. Note that “Black” and “White” are just names; the pieces are not colored. Instead, they are flat, wedge-shaped pieces which point towards the opponent. The identity of a given piece is indicated by two Japanese Kanji characters on each piece. In fact, only the top character is needed to identify the piece and thus only the top character is used in shogi diagrams. I will use alphabetical equivalents in the diagrams here; to see what the Kanji characters look like, start up xshogi (see xshogi) and compare the starting setup there with the starting setup in this file (see The opening setup).

The object of the game is to capture the opponent’s King. The board is a grid of 9x9 uncolored squares, and pieces are placed on the squares. Each player begins with 20 pieces, described in the next section. Capture is by displacement, as in international chess.

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#### 2.1.1 The moves of the pieces

Each player at the beginning of a shogi game has a total of 20 pieces of eight different types. The moves of the shogi pieces can be divided into three classes: “stepping” pieces, that only move one square at a time; “ranging” pieces that move any number of unobstructed squares in a line, and “jumping” pieces that can jump over obstructing pieces to reach their destination squares. Most pieces can also promote to different (usually stronger) pieces under certain circumstances (see the next section). All pieces capture the same way that they move (even pawns). The piece moves and promotions are as follows; each piece name is followed by the standard piece abbreviation:

1. The king (K). The king can move one square in any horizontal, vertical, or diagonal direction, just like the king in international chess. The king does not promote.
2. The rook (R). The rook can move any number of squares in a horizontal or vertical direction. The rook is the same as the rook in international chess (except that it can promote). A rook promotes to a “dragon king” or “dragon” for short (often just referred to as a “promoted rook”), which can move as a rook or can move one square in any diagonal direction.
3. The bishop (B). The bishop can move any number of squares in a diagonal direction. The bishop is the same as the bishop in international chess (except that it can promote). A bishop promotes to a “dragon horse” or “horse” for short (often just referred to as a “promoted bishop”), which can move as a bishop or can move one square in any horizontal or vertical direction. Note: the horse should not be confused with a knight (see below), as they are two completely different pieces.
4. The gold general (G). A gold general can move one square in any horizontal or vertical direction, or one square in a forward diagonal direction. Gold generals do not promote.
5. The silver general (S). A silver general can move one square in any diagonal direction, or one square straight forward. A silver general promotes to a gold general.
6. The knight (N). A knight can move one square straight forward followed by one square to either forward diagonal, jumping over intervening pieces if any. In other words, a knight moves like its international chess counterpart, but forward only. A knight promotes to a gold general. The knight is the only jumping piece, as in chess.
7. The lance (L). A lance can move any number of squares straight forward. A lance promotes to a gold general.
8. The pawn (P). A pawn can move one square straight forward. The pawn captures the same way that it moves, in contrast to international chess. There is also no initial two-space move for pawns and no en-passant capture. A pawn promotes to a gold general; a promoted pawn is usually known as a “Tokin”.

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#### 2.1.2 The opening setup

The opening setup for shogi is as follows:

       9    8    7    6    5    4    3    2    1
    +--------------------------------------------+
    | wL | wN | wS | wG | wK | wG | wS | wN | wL |  a
    +--------------------------------------------+
    |    | wR |    |    |    |    |    | wB |    |  b
    +--------------------------------------------+
    | wP | wP | wP | wP | wP | wP | wP | wP | wP |  c
    +--------------------------------------------+
    |    |    |    |    |    |    |    |    |    |  d
    +--------------------------------------------+
    |    |    |    |    |    |    |    |    |    |  e
    +--------------------------------------------+
    |    |    |    |    |    |    |    |    |    |  f
    +--------------------------------------------+
    | bP | bP | bP | bP | bP | bP | bP | bP | bP |  g
    +--------------------------------------------+
    |    | bB |    |    |    |    |    | bR |    |  h
    +--------------------------------------------+
    | bL | bN | bS | bG | bK | bG | bS | bN | bL |  i
    +--------------------------------------------+

Here, “b” stands for “black” and “w” stands for “white”, so that, for instance, “bL” means “black lance”. The numbers above the files and the letters to the right of the ranks represent the most common notation system used for shogi by westerners (the Japanese also use Arabic numerals for the files but use Japanese numerals for the ranks).

Next: Drops, Previous: The opening setup, Up: The rules of shogi [Contents][Index]

#### 2.1.3 Promotion of pieces

In sharp contrast to international chess, where only pawns can promote to higher-ranked pieces, most of the pieces in shogi can promote. The promoted ranks are discussed in the section on piece moves (see The moves of the pieces) but are repeated here for reference:

Pawn

  promotes to gold general (called a ‘tokin’ in this case only).

Lance

  promotes to gold general.

Knight

  promotes to gold general.

Silver general

  promotes to gold general.

Gold general

  does not promote.

Bishop

  promotes to “dragon horse” or just “horse” for short. The horse can move as a bishop or can move one square in any orthogonal direction.

Rook

  promotes to “dragon king” or just “dragon” for short. The dragon can move as a rook or can move one square in any diagonal direction.

King

  does not promote.

The three ranks furthest away from each player constitute his/her “promotion zone”. A player may, but is not required to, promote a piece after making a move in which the piece begins and/or ends in the promotion zone. Thus you can promote a piece when moving the piece into the promotion zone, out of the promotion zone, or entirely within the promotion zone. Promotion is mandatory in these cases:

1. You must promote a pawn or a lance after moving it to the last rank.
2. You must promote a knight after moving it to either of the last two ranks.

These forced promotions ensure that a piece cannot be moved to a square from which it would have no further move.

Pieces “dropped” onto the board (see Drops) always drop in the unpromoted state, even if they drop into the promotion zone.

Next: Winning the game, Previous: Promotion of pieces, Up: The rules of shogi [Contents][Index]

#### 2.1.4 Drops

When a player captures a piece, that piece is not removed from play. Instead, it becomes the property of the capturer and can re-enter play by being placed on (almost) any vacant square during the player’s move. This is known as a “drop” and counts as a full move (in other words, you can either move a piece on the board or drop a piece onto the board during your move, but not both). All pieces drop in the unpromoted state. Pieces may be legally dropped in their promotion zone, but they do not promote on that turn.

There are several restrictions on drops:

1. A pawn may not be dropped onto a file if there is already an unpromoted pawn belonging to the same player on that file. It is legal to drop a pawn on a file which contains a promoted pawn belonging to the same player, however.
2. A pawn may not be dropped to give immediate checkmate on the move. A pawn is, however, permitted to be moved on the board to give immediate checkmate. This is a curious rule, and if anyone knows the reason for it I would appreciate it if they would contact me and explain it to me :-)
3. A pawn or piece may not be dropped onto a square from which they would have no legal move. This means that pawns and lances may not be dropped onto the last rank, and the knight may not be dropped onto the last or second-to-last rank.

It is entirely permissible (and often advisable) to drop a piece or pawn between one’s King and an attacking ranging piece. For this reason, the final checkmating move is nearly always an attack on the King from an adjacent square (except for an attack by a Knight).

Captured pieces are said to be pieces “in hand”.

The drop is the primary distinguishing feature of Japanese chess, shared with no other popular chess-type game. It gives shogi a very aggressive quality, and dramatically increases the number of possible moves once a few pieces have been captured. Another interesting feature of shogi is that exchanges complicate play rather than simplifying it (as in international chess), because of the drop rule.

Next: Draws, Previous: Drops, Up: The rules of shogi [Contents][Index]

#### 2.1.5 Winning the game

A game of shogi is won by capturing the opponent’s king. In general, this is done by checkmating the king: attacking the king in such a way that the king cannot be defended no matter what the defending player moves. Note, though, that there is no rule that requires a player to defend a king which is being attacked. However, if he does not defend his king, the opponent is entirely free to capture it on the next move, thus winning the game. As in international chess, in practice most games end by resignation when one player realizes that he cannot escape checkmate.

Next: Handicaps, Previous: Winning the game, Up: The rules of shogi [Contents][Index]

#### 2.1.6 Draws

There are very few draws in shogi; only about 1-2% of professional games end in a draw. One reason for this is that material can never be depleted as in chess, because captured pieces are constantly re-entering play as a consequence of the drop rule. In fact, most of the ways a game can be drawn in chess are not allowed in shogi:

- Draws cannot be offered.
- There is no fifty-move rule.
- A stalemate counts as a win for the stalemater. Stated otherwise: if you can’t move, you lose.
- Perpetual check is illegal (see below).

There are only two legal ways in which a draw can occur:

1. A position (including the pieces in hand) occurs 4 times with the same player to move (called “Sennichite”). However, if this is caused by consecutive checks (direct attacks on the King, threatening to capture it on the next move) by one side, the player giving these checks loses the game. In other words, perpetual check results in a loss for the attacker who recreates the same position the 4th time.
2. Both players have moved their King into the the promotion zone (or they cannot be prevented from doing so) and the Kings cannot be checkmated. A King who has entered the promotion zone is known as an “entering King”; due to the forward orientation of most shogi pieces, it is very hard to mate such a King. In that case the players may decide to count their pieces as follows: the King does not count, the Rook and Bishop count as 5 points, and all other pieces as one point. Promotion is disregarded. If both players have at least 24 points the game is a draw (called “Jishogi”). If a player has less, he loses the game.

   Of course, a player can refuse to count pieces when he still has mating chances or chances to gain material which would affect the outcome of the counting. There is no strict rule about what to do if this is not the case, but nonetheless a player refuses to count up (e.g. because he does not have enough points for a draw). It has been generally accepted that in such a case the game ends and the pieces are counted after one player has managed to get all his pieces protected in the promotion zone.

Next: Notes for chess players, Previous: Draws, Up: The rules of shogi [Contents][Index]

#### 2.1.7 Handicaps

Unlike international chess, shogi has a well-established handicap system which is used when players of different strengths play against each other. Handicaps range from small to huge, which makes it possible for weak players to play against even very strong players and have an even chance of winning.

Shogi players are ranked as follows: the weakest rank is around 15 “kyu”, which represents a beginner. 14 kyu is higher than 15 kyu, 13 kyu is higher still, and so on until you get to 1 kyu. The next highest rank is 1 “dan”, followed by 2 dan, 3 dan and so forth. The highest amateur rank is 6 dan; professionals go up to 9 dan. However, professional ranks are not the same as amateur ranks; a professional 1 dan is much stronger than an amateur 1 dan. This system is similar to that used by go players (and also other Japanese sports such as karate).

A handicap consists of the stronger player playing White and removing one or more pieces from his side of the board at the start of the game. These pieces are permanently removed from play; they are not in hand.

The following is a list of the accepted handicaps, from weakest to strongest. The degree of the handicap, represented by the position in the list, represents the difference in rank between the two players for which the handicap is appropriate. These rules are taken from the books “Shogi for Beginners” by John Fairbairn and “The Art of Shogi” by Tony Hoskings (see References and links) and, I believe, represent current Japanese practice.

1. The stronger player removes his left lance (on 1a).
2. The players play a two-game match; in the first game the stronger player removes his left lance (on 1a), while in the second game he removes his bishop.
3. The stronger player removes his bishop.
4. The stronger player removes his rook.
5. The stronger player removes his rook and left lance.
6. The players play a two-game match; in the first game the stronger player removes his rook and left lance (on 1a), while in the second game he removes his rook and bishop.
7. The stronger player removes his rook and bishop. This is usually called a “two-piece” handicap.
8. The stronger player removes his rook, bishop, and both lances. This is called a “four-piece” handicap.
9. The stronger player removes his rook, bishop, both lances, and both knights. This is called a “six-piece” handicap.
10. The stronger player removes his rook, bishop, both lances, both knights, and both silvers. This is called an “eight-piece” handicap.

Another advantage of playing handicap games is that the handicaps alter the optimal strategy for both players. For instance, handicaps all have their own opening lines which may bear little or no resemblance to those used in non-handicap shogi. This means that when learning handicap shogi, you are essentially learning completely new games which use the same equipment!

The reader may wonder how on earth a player giving an eight-piece handicap, say, could possibly hope to win. Don’t forget, though, that in shogi the opponent’s pieces can be captured and then become part of one’s own army. Thus, if the opponent plays badly enough, the number of pieces will soon even out.

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#### 2.1.8 Notes for chess players

Here are a few miscellaneous things that may confuse chess players. Some of these have been mentioned elsewhere, but they bear repeating.

1. There is no queen.
2. Pawns capture the same way they move. There is no initial two-space pawn move and no en-passant move.
3. There is no special castling move. There are a large number of possible defensive formations referred to as “castles” (see Sample game) but there is no need for special moves to create them.
4. A given piece can only promote to one other kind of piece.

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