Chu Shogi

Chu Shogi (中将棋, Middle Shogi). First documented ~1350 AD. The dominant form of chess in Japan for centuries until modern Shogi replaced it.

Overview

Chu Shogi is played on a 12×12 board with 46 pieces of 21 different types per side. Unlike modern Shogi, there are no drops. The defining piece is the Lion, a double-move piece so powerful that special rules govern its capture to prevent quick trades.

Win condition: Capture all of the opponent’s royal pieces. There is no check or checkmate — the game continues until the last royal is captured. Stalemate is assumed to be a win for the side delivering it.

Starting Setup

Pieces are listed by file (a–l = left to right from White’s perspective) and rank. White occupies ranks 1–5, Black mirrors on ranks 8–12.

Rank 1 (back rank)

Rank 2

Rank 3

Ranks 4–5

Key Pieces

Lion

The Lion makes up to two moves per turn, independently in any direction (even changing direction after the first). It may:

• Move or capture to any square within a 5×5 area around it
• Capture a piece, then move or capture again as a King
• Move to an adjacent empty square and return (passing the turn)
• Hop over a square (if moving to the same destination in one leap, with the middle square occupied)

Kirin

Leaps diagonally one square (Ferz) OR leaps exactly two squares orthogonally (Dabbaba). Promotes to Lion.

Phoenix

Moves one square orthogonally (Wazir) OR leaps exactly two squares diagonally (Alfil). Promotes to Queen.

Drunk Elephant

Moves one step diagonally in any direction, or one step forward/sideways orthogonally (cannot step backward). Promotes to Prince (a second King).

Promotion

Promotion is optional and occurs when a piece enters the promotion zone (the four ranks farthest from the player: ranks 9–12 for White). A piece can also promote when it captures inside the zone. Each piece may promote at most once regardless of its position.

Pawns may promote even without a capture upon reaching the last rank.

King, Lion, and Queen do not promote.

Horned Falcon and Soaring Eagle have limited Lion power in one/two directions respectively: they may make two consecutive steps along the same ray, continuing after a capture.

Prince (Two Royal Pieces)

A Drunk Elephant that promotes becomes a Prince — a second royal King. When a player has two royals, losing one is non-fatal; only losing the last royal loses the game.

Lion Capture Restrictions

To prevent quick Lion trades, two rules apply:

1. No protected trade: A Lion may not capture a protected enemy Lion if doing so exposes it to recapture (as if it were an absolute royal for one move).

• Exception: A Lion may always capture an adjacent enemy Lion (which could take it “in passing” regardless).
• Exception: A Lion capturing the enemy Lion together with at least one other non-trivial piece (not a Pawn or Go Between) may do so even if exposed to recapture.

2. Counter-strike rule: A non-Lion may not capture the enemy Lion if on the immediately preceding turn the enemy captured a friendly Lion using a non-Lion.

• Exception: Promotion to Lion during such a capture allows the fresh Lion to be recaptured.

Repetition Rules

Repeating a position (same side to move) is forbidden. Per the Japanese Chu Shogi Association:

• Perpetual check: the checking side must vary.
• If only one side is attacking with all moves since the prior occurrence, the attacker must vary.
• If both sides are only passing, the side that began passing must vary.
• If neither side attacks anything, a draw may be claimed.
• Otherwise, the side whose move caused the repetition loses.

(Rules trigger on the 4th repetition, as in modern Shogi.)

Baring Rule

King + any piece vs. lone King is a win, by convention, for the stronger side. Some interpretations extend this to a full bare-king rule (any pieces remaining = win), but this is disputed.

Source: chessvariants.com/rules/chu-shogi (H.G. Muller)