What is the rib in xiangqi?

These answers restate the rules implemented by our open-source engine, which follows the WXF laws for movement, checkmate and both repetition rulings: a side that forces a repetition by perpetual check or perpetual chase loses rather than drawing. The chase half has not been validated against the official casebook. Where an answer refers to a specific position, that position lives on the linked reference page, where the build verifies it before publishing.

Why the rib matters

The general lives on three files: the centre and the two ribs. If a chariot controls one rib, the general cannot step onto that side, and any check down the centre file becomes much harder to meet. A chariot on the rib also aims at the palace's corner points, where the advisors stand, and can pin or attack them. A chariot occupying the rib is one of the standard attacking set-ups, and a common attacking plan is to get a chariot onto the rib with tempo.

Rib and centre together

The centre file belongs to the central cannon and the general; the ribs belong to the chariots. Combine them and the general runs out of room: one piece checks down the middle while the rib piece covers the side step. Many mates in the checkmate patterns are built this way. See attacking the palace for how the pieces divide the work.

Defending the rib

As defender, keep an eye on your rib files. An advisor on its corner point blocks one, and the general itself can step onto a rib to escape the centre. The danger is the moment an enemy chariot reaches a rib with your advisors unable to cover it. Trading off the attacker's chariot, or blocking the file early, is usually cheaper than defending against it later.

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