Rules for playing Chu Shogi

Introduction

Chu Shogi (Middle Shogi) is a very ancient game. It was mentioned in diaries as long ago as the twelfth century and therefore predates modern Shogi (and the modern game of Western Chess) by centuries.

Chu was the most popular of the enlarged forms of Japanese Chess, and still had many adherents in parts of Japan until very recent times. Chu Shogi is the only variant (except Shogi itself) for which sets are still commercially available in Japan.

There are many unusual and powerful pieces which make Chu a very exciting and challenging game. The game is dominated (particularly in the early stages) by the Lion, a piece totally unlike any piece in Western Chess.

There is no provision for returning captured pieces into play in Chu; the game may therefore seem more familiar to players of the western game than modern Shogi.

The Game

Chu Shogi is played on a board of 12 x 12 squares and each player has 46 pieces (including 12 pawns).

As in all Shogi games, the pieces are flat and wedge-shaped and are not distinguished by colour. Although the pieces are of uniform colour the first player is still conventionally referred to as Black and the second player as White. Ownership of the pieces is indicated by the direction in which they face, with a player's pieces always pointing towards the opponent.

The players make alternate moves, with the object being to capture the opposing King. If the opposing player has obtained a Crown Prince by promotion, that piece must also be captured in order to win the game.

The game can also be won by capturing all pieces except the King (the Bare King rule), if you only have a Gold General left on your side. (This interpretation is due to George Hodges). Note that this only makes a difference to the result if (without this rule being in force), the opposing King could immediately capture the Gold General, thus getting King versus King (which would be decided by the repetition rule).

On each turn a player can move one piece according to its power of movement to a vacant square on the board, or to a square occupied by an enemy piece (in which case the enemy piece is captured and removed from the game)

In the case of the Lion and pieces with Lion power a second move can sometimes be made in the same turn.

The Pieces

The Piece Help screen provides the names, notation symbols, promotion details, and powers of movement for all of the pieces in the game. The Pieces

Jumping Pieces

The Kylin and Phoenix (and those pieces with Lion powers) are the only pieces in Chu Shogi that have the power to jump over occupied squares. As indicated by red circles on the Piece Help screens, the Kylin can jump to the second square in any orthogonal direction, and the Phoenix may jump to the second square when moving diagonally.

The Lion

The Lion has a very unusual move, and a number of special rules involving its capture.

If the 8 squares immediately adjacent to the Lion are called the A squares (shown as Dark Blue Circles on the Piece Help screen), and the 16 squares two away from the piece are called the B squares (represented as Light Blue Circles), then the Lion may do anyone of the following things in a single turn:

• Move directly to any A or B square, jumping an intervening square if necessary;
• Capture a piece on an A square and continue moving one more square in any direction from the point of capture, making another capture if the 2nd square is also occupied by an enemy piece.
• Capture a piece on any A square without moving (this is known as igui and counts as a turn).
• Move to an adjacent square and return to the starting square (effectively passing the turn).

The following restrictions apply to the capture of Lions in Chu Shogi:

• A Lion may capture an opposing Lion on a B square, only if it also made a capture on an A square (unless the captured piece was a Pawn or Go-Between), or if the opposing Lion is undefended.

  Should your Lion be attacking an opposing Lion (on a B square), but it is so positioned that it is between the opposing Lion and an otherwise unobstructed protecting piece, then the opposing Lion is still protected, so it cannot be taken by your Lion. The defending piece is called the Hidden Protector.

  The question has been raised (by Nick Bardsley) as to whether a double-capture should invoke the hidden protector rule, if the first piece is a Pawn or Go-Between, and the presence or absence of this piece affects the hidden protector rule. After much consideration, I have come to the probable conclusion that the hidden protector rule does not apply in this circumstance (and that is how the program actually behaves). This could be a matter of debate.

  A Lion may capture an opposing Lion on an A square at any time, without restriction.

• If a player captures a Lion with a non-Lion piece, the opponent may not capture a Lion except with another Lion, on his very next turn.

These rules ensure that the Lions which are the most powerful pieces in Chu Shogi are on the board for most of the game.

The Horned Falcon and Soaring Eagle also have Lion power, but only in the directions indicated by Blue Circles on the Piece Help Screens. There are no special rules concerning the capture of Horned Falcons or Soaring Eagles.

The Crown Prince

The Drunk Elephant is potentially a very important piece, as it promotes to a Crown Prince.

A player who gains a Crown Prince effectively acquires a second King as the Crown Prince must also be captured (or bared) before the opponent can win the game.

Promotion

Each player has a Promotion Zone consisting of the four ranks (rows of squares) furthest away from him. All pieces except the King, Lion and Free King have a promoted rank and can promote on entering, moving within, or leaving the Promotion Zone. Promotion is not compulsory, but is subject to the following restrictions:

• If a piece does not promote on entering the Promotion Zone it may not promote on it's next move unless making a capture. The piece may, however, promote on any subsequent move (as long as part of the move is within the Promotion Zone).
• If a Pawn is not promoted on entering the Promotion Zone, it must remain unpromoted until reaching the last (twelfth) rank, at which time it must promote.
• A Lance must promote on reaching the last rank (as it would otherwise have no further legal move).

Capture

Unlike in Shogi, captured pieces in Chu can not be dropped back into play. A captured piece is removed from play and takes no further part in the game.

Handicap Play

There are at least two different systems for handicap play at Chu Shogi. At some point in the future, this program will implement the elaborate system given on page 49 of the Middle Shogi Manual

Notation

The following notation system is used for recording Chu Shogi games in this program.

The files are designated by numbers (1 to 12), and the ranks by letters (a to l). The files are numbered from right to left (in the Japanese fashion), and the ranks from top to bottom (from Black's point of view). The top right square is therefore 1a.

A move is described by giving:

1. The number of the move, according to western customs.
2. The designation of the piece (eg: Ln for Lion); this designation is preceded by a '+' if it is at its promoted rank,
3. Then the starting square,
4. Followed by the method of moving;
   • '-' for a simple move on the board,
   • 'x' for a capture,
   • 'x!' for an igui capture,
   • '!' for a pass move,
5. Then the destination square is recorded,
6. Finally if the piece promoted on that turn, this is recorded by adding '+' after the move, or if promotion was possible but was refused, the symbol '=' is added.
7. When a piece makes a double capture with 'Lion' powers both captures are shown in the order that they were made. (eg: a Lion on 3g capturing a piece on 3h and then capturing another on 2i, would be represented by Ln 3g x 3h x 2i).
8. This system is based on the official notation system of 'The Shogi Association', but has differences; the main one being that in the official system the starting square is only included if more than one piece of the same type can reach the destination square. This program has provision for supporting this in the future, but I can see no good reason for doing so.

Touch and Move

The rules of Chu Shogi specify a strict rule for touch-and-move. This program will attempt to simulate these restrictions, if you select the tournament mode from the Options menu (this is for masochists only, but it is good self-discipline).

Repetition

Repetition is forbidden in Chu Shogi. This program reinforces the rule by not allowing a move to a position that has occured before, with the same player to move. If you make such a move, you are forced to take it back, unless you have turned on tournament mode, in which case you lose.

In Mating Mode, the rule enforced is that Black must vary.

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