How do a cannon and chariot combine on the same file?
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.
Direct answer
With the cannon behind the chariot, the chariot is the cannon's screen, so both attack the first piece beyond the chariot. That piece is attacked twice, and a defender who puts a piece in front of the chariot to stop it simply offers that piece to both, which is why this pairing is so difficult to defend cleanly.
Why blocking the chariot rarely helps
A piece placed to stop the chariot's advance along the file becomes the first piece beyond the cannon's screen the moment it lands there, so it is attacked by the cannon as well as the chariot. The exception is a check: a piece interposed between a checking chariot and the general blocks the cannon too, because the cannon then has two pieces in front of it.
Setting the pair up deliberately
Placing a cannon behind a chariot on the same file, rather than in front of it, keeps this option available: the chariot leads and threatens directly, and the cannon behind it adds a second attack on the first piece the chariot meets. See 馬後炮 for the same behind-the-front-piece idea with a horse instead.
Related questions
Does the order on the file matter?
Yes. The cannon usually gets more from being behind the chariot than in front of it, since the chariot then serves as its screen.
Is this pairing common in the opening?
Yes, it is one of the standard ways a Central Cannon attack is reinforced once a chariot's file opens.
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